DANGEROUS to Drive! Ram Camper Van STALLS after Hot Soak - Part 1

The owner of this mint Dodge Ram 3500 Camper Van says this truck is DANGEROUS to drive after a hot soak. It's reluctant to start, and STALLS out at stop signs and traffic lights...not a safe situation!
He's taking it on a cross-country trip soon, and wants the issue fixed before making the trip.
Let's see if we can make the big beast act up, and figure out what's wrong without firing the parts cannon.
Enjoy!
Ivan

[@jackpatteeuw9244]

I am familiar with the Ford idle speed algorithm. First, you have to understand the engine operates in 3 different modes: closed throttle, part throttle and WOT. The modes are determined by the TPS. If you are in closed throttle mode and you add a small amount of throttle, not enough to enter part throttle, the ECM algorithm WILL take away IAC ! If you add enough throttle to enter part throttle mode, you are correct in that the IAC will pre-position for when you take your foot off the throttle. There is no direct feedback from the IAC. The ECM believes that if it commands X number of steps, the IAC actually moved that many steps. The current position, in steps, is created during engine cranking. First, the IAC close completely (0 counts) and then it steps forward to it's starting position. Now it knows where it is at and all additional steps are added or subtracted from that number.

[@jump429]

I went through this with fleet of full size Ram vans in the early 2000s all had similar problems. You will probably find it will act up not want to start vapor lock even run bad if the fuel tank is low and you drive it around for a while. All of the vans I was working on had the filter/sponge in the tank clogging if you do a volume test when they were acting up the fuel would start to spit out, pump was cavitating I found the filters clogged around 100K. Driving would slosh around the fuel cause it to start running better or full up tank would run better crazy pain to figure out at first and before I figured out the first one had 2 more doing same thing.

[@DavidGuns]

I had a 2001 Dodge Van and was doing almost the same thing after a hot soak. Turned out to be the PCM/ECM due to the circuit board inside was cracked and when it got hot the crack would open up more stalling it out.

[@hikerJohn]

Good comment but this one runs fine hot. Did yours act JUST LIKE this one, only acting up after you turned it off? (trying not to watch to the end before reading comments) :o)

[@DavidGuns]

@@hikerJohn same symptoms

[@txdm9383]

I'm thinking since it seems like the battery is weak the battery voltage is dropping too low during cranking and the PCM is losing it's learned idle memory, the throttle body is probably dirty as well compounding the issue.

[@mattcat231]

I have seen this exact thing 3 different times and it was 3 different issues every time, 1997 Dodge Dakota 5.2 had a PCV valve issue where it was pulling oil, then it would only idle with the IAC at about half open (43%). Next was a 1998 Dodge Ram 5.2 that sounded an awful lot like this van, the starter was drawing so many amps that it was pulling the keep alive memory out of the ECM causing an idle relearn every time it was started. Next was a 1998 Dodge Durango 5.2 that had an intake manifold gasket leak, which had me chasing my tail because they usually leak when cold, but this one was leaking into the lifter valley and not at the top by the valve covers. Gave it the Charleroi Chimney, aka Avoca Smoka, and found it that way

[@randy1ization]

the loss of comm error that kept popping up may support your theory of the Iac trying to do relearns. Im wondering if it has a bad main ground somewhere. its also sluggish to turn over the engine..

[@AlexHernandez-sc4vg]

PCV, I like this idea aswell

[@Tomsfoolery.]

The pintle on the end of the IAC motor may be dirty. Back in the dealership days, we ran into similar situations on the magnum engines and cleaning the pintle on the IAC would straighten things out. That being said, we also had several PCM failures that would often give similar symptoms. Looking forward to part 2!

[@jeffcompton6937]

I was thinking from the 5 minute mark of this video if you've worked on a pile of old dodges like I have you should already be looking at your battery condition and the alternator output. It sounds just like it has to relearn idle rpm everytime you're starting it which it shouldn't need too unless the battery is to weak and the ecm keeps resetting that value

[@letzrockitrite8469]

I had a similar symptom on an older vehicle.... it was the electronic ignition module inside the distributor cap.... back in the day it turned out to be a recurring bad batch of them but it was replaced in Oregon, Utah and Colorado on a nightmarish trip... I know those folks will be grateful Ivan

[@classicwefi]

A weak battery or voltage drop in the battery cables will cause this problem on those magnum engines it causes the pcm to loose the learned IAC steps until you have a key cycle and restart with proper voltage. Cleaning the throttle body would be a good idea. I fixed a lot of these working at the Dodge dealer .

[@roberthammond6232]

Throttle body cleaning should be regular maintenance on this vintage Chrysler. The V6 run very poorly with a dirty throttle body.

[@randy1ization]

yes, the sluggish cranking and comms loss are both big clues.

[@kc360awareness]

I have been looking for this exact comment. Had a couple of these in a church van fleet…. Dead or low battery would cause then to lose their learned idle.

[@kevincrawford6734]

Well done Robert, Think simple....always works with old Mercs..😊

[@randy1ization]

@@kc360awareness most batteries nowdays are junk. they lose charge fast when not started or maintained regularly. neighbor bought a new wallmart battery 6 months ago, he let the car sit and rarely started it.. he came over wanting help to change the alternator , insisting it couldnt be the battery. I jumped the car, and checked the alternator, it was good. tried charging the battery, would not take more than 6.5 volts from my commercial charger,, he took the NEVERSTART battery back to wallmart and they changed it out. problem solved.. used to be u got a 5 to 7 year prorated warranty on batteries, now I think 3 is the most u can get, because they KNOW the batteries arent going to last. also 90 percent of all batteries sold in the US are made in Mexico and they slap different brand stickers on them.

[@baxrok2.]

Thanks Ivan!

[@bellasvistas3463]

I keep refreshing your page looking for the next video. I hope it will help me fix my van.

[@alialjuboori7968]

Let's go bro! I appreciate the way you teach and explain things 💯 much love ❤️

[@rickgalla3377]

Great video Thank u from staten island

[@roxanneabbott8424]

My first thought was dirty throttle body, but what do I know? Cant wait for part 2 Ivan!!!

[@PineHollowAutoDiagnostics]

Roxanne you know more than you think 😉

[@Dirtyharry70585]

@@PineHollowAutoDiagnostics think sma beat you on a jeep

[@roxanneabbott8424]

@@PineHollowAutoDiagnostics thank you Ivan!!!

[@russellhltn1396]

When you first described this, I wondered if this was a variation of the old vapor lock situation - the gas in the fuel rail would boil and cause all kinds of problems. Given this is a return-less system, all that vapor would have to be consumed before things got back to normal. I'd be checking the fuel pressure. Maybe I'm wrong, but that would be a fast easy check to rule out weak fuel pump or pressure regulator. In fact, I'd do that before starting a deep dive into the computer readings.

[@heatmizr13]

Load shedding might be a possibility. Your skills and knowledge are outstanding Ivan.

[@HotRod-wv4vm]

Can’t wait to see P2

[@Super8_150]

Air filter, pcv, throttle body clean, IAC clean, fuel filter, fuel pump, new battery, and for sure new wiper blades. That's my parts cannon burst from the keyboard. If none of that works, then PCM. If that doesn't work, then heat shield all fuel lines. If that doesn't work, then send it to Rainman Ray. If that doesn't work, have Ray send it to South Main.

[@IDKWTFID]

STOP MAKING US WAIT LOL

[@AntonioClaudioMichael]

Good morning bro @Pine Hollow Auto Diagnostics

[@antoniomancini4894]

I am sure you will figure it out because you are the greatest at figuring things out great Channel

[@brianm9007]

Alright, I'll throw my hat in the ring. Assuming the logic in the computer is not corrupted, could it be closing the IAC while simultaneously opening either the purge valve or the EGR? It would assume the extra air lost from closing the IAC would be compensated for by the extra air added from the purge or the EGR system? I know you tested the purge valve, but you tested to make sure it wasn't leaking, correct? But, if the purge wasn't OPENING under command, or the line was restricted/blocked (or the canister the same), this would prevent the extra air from being added by the EVAP system. This would also explain (maybe!) why it happens after the engine has warmed up.

[@AP9311]

Very interesting diagnosis Ivan. It sounds like the iac isn't commanding correctly. Looks aftermarket part. But i don't know to much of the iac stuff. But I'd say you're on the right track. I'll wait see part 2!! Awesome explanation of your version of the issues on it. Great job!!

[@billsmith2212]

From my experience on my 1987 GM , they can sometimes get a build up of carbon around the pintle . When it had worn , there were rub marks where the pintle would seal against the plenum . I suspect that was side play in the shaft . Nothing wrong with a relearn . And if that is an off brand replacement , it could be a joker in the deck !

[@nct9466]

I had a Chinese motorcycle (CSC RX3 as in USA) and it would do a similar thing with carbon on tip and inside the passage as it used this type of Delphi AIC....

[@brianr9049]

i had similar symptoms with my old Chrysler and every time it was a dirty throttle body, but who knows, it could be many things. i don't recall if it only did it after driving it for a period but i do specially remember you could tap the gas at traffic lights to keep the engine running lol

[@johnleinen7167]

Ivan, note the starter is getting ready to give up, more than likely its original and these sound exactly Ike that.

[@KarateSensei71]

I worked for GM/Delphi for 40 years in Product Engineering, your thought process is 100% spot on and you followed a very convergent problem solving method, love your videos.

[@blueskiesmobileauto4253]

Cool issue Ivan! The van sounds like the classic Chrysler start and die after a battery disconnect. I wonder what the default steps would be if you were to unplug the iac while it was running. Looking forward to the fix!

[@cullenmiller8170]

Awesome video. A friend of mine owns a 2000 Dodge Durango with the 5.9 ltr engine. It has a problem on cold start below 40 degrees Fahrenheit. It's a start stall You feather the throttle to keep it going and after it warms up it runs perfect. I had a launch scan tool and couldn't find any helpful data. Now that I bought a used Verus I'm hopeful. Specially after watching this series I might be able to figure it out. It seems like all the inputs it would use looked fine when looking at data pids. Go Ivan go. 😂

[@lvsqcsl]

We had a 2001 Dodge van as a company truck and the purge solenoid was indeed sticking. Took a couple of tries, but the dealer finally got the issue corrected. I think that was almost the last year they made those. 2002? Great video!

[@tallbrian100]

House wiring Romex in the engine bay. LOL

[@fiero880]

I had a weird similar issue on a 94 GC 5.2. I didn’t have a scanner and after chasing everything done the hard way, the purge solenoid was allowing fuel vapors to enter the throttle body at idle and would killer the engine or make it run horrible for a short period of time. I found two bad vacuum check valves and possible bad signal wire from the pcm. Now your engine is the 2nd or 3rd gen vs the 94 I was working on. But the circuit was powered by a 12 v supply and the pcm would supply ground to the purge solenoid to activate it. Once activated it would not complete the vaccum to not command vapors into the intake.

[@flatdaddio]

Wow, I'm getting the same thing with my 2004 Lincoln. Took it to a shop they changed the plugs and coils and it still happened after. They kept it and could not find the problem. My car has stalled, but most of the time I get misfires until I drive down the road. I was looking at the IAC, but I also suspect there may be an issue with the EGR. I can't wait to see what you find!!

[@Sandmansa]

I have to agree with you on the scanners Ivan. My Launch pad 2 and Thinktool pros have the exact same limitations on some vehicles. This is why I also keep a Snap-on Tritan D10 around to help with the other things my go-to scanners can't do. Now for the ram van.... My guess is the IAC is getting stuck in the bore. It might just be gummed up with carbon. Also sounds like the starter motor is getting really tired. Might be worth suggesting replacing that before the owner takes off on a long trip.

[@hometownautomotive2110]

Used to be common on Mopars for the purge canister to leak small grains of charcoal. The small grains would get caught in the purge valve holding it open. Usually presented as hard start after fill up as the partly stuck open purge valve allow the fumes to be forced into the intake while filling the tank. But would also happen after hot soak if some of the charcoal was stuck in the purge valve. Usually you could just remove the purge hose and shake it and find small particles falling out. Also may explain the low stepper #s trying to make up for the vacuum leak

[@edwinlomonaco6754]

Now that I'm watching. I also thought checking the throttle body for build up. Sometimes the iac is working too hard to keep the engine running due to the throttle body being dirty.

[@TheOriginalDaveJ]

I think this. Maybe the throttle body needs a clean as it's sticking. Computer is trying to compensate for this through the IAC. If it was anything to do with the EGR it would be down on power throughout the gears (possibly)

[@brycelund4112]

This problem only happens when it’s hot. That would rule that out as a possible issue.

[@litz13]

Well, this is basically what the Sea Foam cleaning does, as it'll get sucked right through the IAC as part of the process.

[@johnwaby4321]

That's a nice problem Ivan 👍👍

[@AntonioClaudioMichael]

I agree Failing fuel Injector and or leaking and the bad purge solenoid being stuck open sounds more realistic on the symptoms @Pine Hollow Auto Diagnostics

[@ferrumignis]

The IAC (Steps) reported parameter is only telling you how many steps the ECU has applied, the ECU has no way of knowing the actual position of the stepper. If it's intermittently sticking and losing steps or not able to be driven fully to it's home position to get the zero step position then you would expect the reported step value to change as you are seeing.

[@nickmalone3143]

Shouldnt the motor re-home with key on to reinitialize the step counter ?

[@boogerhead0]

@@nickmalone3143 It will, but again may immediately lose steps if gunked/sticking.

[@ferrumignis]

@@nickmalone3143 Yes, it moves to one end of its range to zero the step count but if part of the steppers range of movement is bad (i.e. sticking) then it could get a bad home position or it could lose steps immediately after getting home amd moving to the stored open loop idle value. It seems to be able to control idle pretty well sometimes, so I suspect only part of the motion is tight rather than all of it.

[@sewing1243]

If it had a carburetor I'd suspect vapor lock in the fuel lines or the carburetor due to heat.

[@calholli]

I wonder if your ThinkTool pro would have the IAC pid under basic OBD2 data? Just a thought.

[@DaddyBeanDaddyBean]

When those exact symptoms happened on my car, they diagnosed a bad power valve; I rebuilt the carb and it ran much better. I don't think that is the problem here though. ('65 Mustang) 😁

[@mathewfarnsworth1860]

Just had a similar issue with a 5.3 and noticed 5 minutes after shutting down the pressure would drop so put the shut off valves on the fuel lines and isolated the pressure on the rail and still dropped and so got new used injectors and solved the problem. Was basically flooding the engine causing long cranks. But like you said mine cleared right up after starting and ran fine.

[@antoniomancini4894]

My guess is EGR valve although I'm going to continue watching great Channel

[@patrickengle9344]

heat's been known to damage/distort coils/ICMs on vehicles in which the modules are placed in the distributor or on the body. A 93 camry had a problem in which the coil was placed in the distributor eventually warping the housing but what was strange the ecm cut off the fuel injectors suggesting a fuel problem because it detected an "over heat" situation, a Ford aspire had the same problem with overheating ICMs

[@theemooneys]

I remember one time back mid 90 on a hot summer day a lady came out of the store and her dodge truck had a crank no start. It had the old school throttle body injection. I opened the throttle fully and closed it and the truck started and ran fine. I had a neighbor with an 80 Lincoln that was hardly driven. Ford mechanic told him if it would not start to push the accelerator to the floor once and then start it. Must be pressure build up in the intake.

[@Kacavida11]

6:20 whisky tango foxtrot, theres a kid in the back, ... oh... its a photo, huh thats a good one

[@jeffbaldwin9842]

I think you said it yourself: kinda slow to crank. I'd start with the battery. Good stuff!

[@bernardaflores1720]

Time to sent a quick message to customer service from Think Tools. It is crazy what some scanners can do while others not so much!

[@jamesallen9366]

Father in law had the same problem with 2000 ram pickup 2500. His was a bad tork converter. Locking in at low RPM at red lights! She's a beaut Clark!

[@blueribb99]

I have a 98 Jeep Grand Cherokee 4.0L that had intermittent low idle, almost causing it to stall when stopping at traffic lights. I put up with it for a while and last year decided to try a new OEM IAC, which was very expensive ($155). I no longer have intermittent low idle. I also had a weak battery which caused a similar issue with both idle and stalling. I forgot to mention that reading the comments on Amazon for the IAC Motor, they said DO NOT buy a cheaper aftermarket part - only buy OEM. There was a HUGE difference in price, but I bought the OEM as recommended.

[@calholli]

For the IAC not being there on your thinktool -- if you just file a report to them about it missing, they will know that it needs to be updated and get it fixed. I know on the Xtool's, they are good at fixing bugs like this within a week or two, and they have nearly a dozen updates everyday; luckily I have 3 years of free updates... Also, I wonder if IAC would have been there if you checked under basic OBD2 data on your thinktool?

[@jtjones4727]

Could it also be that you overlooked it? I think they may all be listed as AIS or related to AIS, or adjusted idle speed or something like that.

[@ecaparts]

It’s not a bug, just a missing PID or feature. We are talking about a 22 year old Dodge. I don’t think they care. In the past, I reported a glitch to LAUNCH when I was having a problem with a special function on a GM. Never heard anything and nothing came of it. These Chinese scan tools have many problems but they overall work good enough. It is what it is. Even a $10,000+ scan tool from Snapon doesn’t get you any special support. When there is a glitch you can bend over and pay to upgrade and see if anyone listed to you…

[@autotek7930]

My company works directly with Autel and we can send reports to them and they always fix our issues. The thing is a lot of our techs don't report them lol. We also help develop special service tools especially for ADAS

[@bluegizmo1983]

I've got a very similar problem with my 1995 GMC Sierra 1500 4.3L TBI. Runs great most of the time, but on really hot days in the desert where I live, like 90+ degree days, once the truck heat soaks is start choking and stalls. The difference is with mine, giving it more throttle makes his choke worse and die faster! Once it happens the only solution is to roll to a stop and let it cool down for about an hour then it's fine again. Pretty sure it's not the TBI either, as I replaced the entire TBI unit and it's injector with a brand new unit and it still happens. It's an OBD1 vehicle too so I can't get any useful information from it like an OBD2 vehicle.

[@JohnStoneNC]

Van needs its throttle body cleaned and has a dirty pintle on the IAC. Clean it all with scotch brite pad and some carb cleaner. Good as new.

[@alansoccer2003]

My money is on a dirty iac and throttle body. If I remember right base idle on the older dodges are. Like 550-600 and the iac is almost closed at idle

[@Mark-om4jr]

I agree. That has been the issue 99% of the time in my case's.

[@alanmcclelland5245]

Only on hot start ?

[@vpimike2646]

You are definitely on the right track, Ivan. I would check each of the inputs to the ECM that it uses to control the IACV. All cars vary, but typically the ECM monitors load parameters from A/C, headlights, rear window defogger, power steering pump pressure switch, neutral start switch, etc. Perhaps your research service will explain how the input parameters impact the ECM's strategy to control the IACV. I know you already have this figured out and I'm looking forward to your resolution in part 2. 😊

[@willemstreutgers1154]

Seen the trottle% staying extreme low during this hot soak so check the trottleposition sensor signal plse. Also lost comm. during cranking due to worn battery will cause lots of weird probs.

[@rjm7168]

I think the bootstrap generator has defromenized ... 🤪

[@brianw8963]

Interesting for sure. My thoughts would be a guess at best, so I’ll wait till tomorrow and say “that’s what I thought”.

[@boomer9900]

Heat + electronics can lead to problems. Unrelated, but 2 interesting stories to tell. 1. Ford Ranger - failed to restart after hot soak, first a small problem then progressed to 45 minute wait. Turns out it was a broken wire in the ignition coil that was ok when cold, but went high resistance when hot. 2. Chevy Celebrity - MPFI 2.8L V6 - cold start problem. On cold start the idle would vary up and down for 2 minutes until engine stabilized. The IAC was going in and out in and out. It went in so much that normally a cold start required 3 times with the key to stay running. This was a real head scratcher. Issue was faulty "cold start fuel injector". Some cold start injector unrelated to the 6 main injectors was supposed to spray for a few seconds after cold start and cut out with bi-metallic strip. This strip failed so it got less fuel on initial start and threw the computers idle regulation strategy completely nuts for a cold start, as the computer hunted for the proper idle. The algorithm failed because it depended on this extra injector fuel at start. That one was tough. For this one I'm waiting for pt. 2, it could be so many things. Try unplugging the IAC when it is at the correct number of steps 88 or so and then try starting the engine when it's acting up and bam you know its at least iac related for sure.

[@johnz8210]

I'm thinking I'd have that air filter off next and see how dirty the TB is, air filter itself, and check the battery - it does crank kind of slow. Those didn't like a weak battery. Then go from there.

[@peterbenson3776]

What else effects the response of the IAC valve? Any other variable factors?

[@coreybabcock2023]

Yep the regulator is part of the fuel pump assembly and I had to change the assembly out by cutting a square hole in the floor of the van I had I should have kept that van and repaired it but it's been over 2 years now and I had a 03 ford Taurus ses too

[@danieldavis8651]

Probably should check the engine temp sensor as well I believe that plays on how the iac functions.

[@scientist100]

Fuel delivery is what is affected by coolant temp.

[@killerclown1740]

I was thinking the same thing.

[@Iceeeen]

Was really annoyed when he had everything selected except engine temp. It's the number one thing to check with this kind of behavior. Especially the blue bosch sensor always seam to go bad this way. Good from cold but gives way to warm reading on a warm start and the engine runs lean

[@Arnthorg]

Iac stiff and is missing steps or some other variable vacuum leak since the steps were continuously changing at idle?

[@hpelisr]

The motor of the IAC is sticking and not adjusting to command, forcing the computer push numbers down. I would also look at intake a little closer.

[@antonoudenhoven7573]

My car had the same issue,turned out to be the head gasket. But there are so many things that could cause this problem

[@TheOmegaman69]

As usual, a very interesting case. I would, off the top of my head as I haven't looked at service manual or schematics or anything, that depending on how the ECM determines the engine load, this may or may not be a possibility. If after a heat soak say maybe the alternator is hot and misreports the load (current draw), assuming the ECM determines load from the current draw of the alternator, rather than looking at a lot of sensors individually, the latter which is possible of course. Then once engine is running a few minutes the alternator (or some current sensor if equipped) starts working normally and engine runs good. Seems that monitoring the current load of the alternator would be a more efficient method of determining the load than looking a many individual sensors, which I sure the ECU does do for many things. I do not know for sure how the load is determined by the ECU on this particular vehicle. One test that could be done would be to do a heat soak then turn on some loads, headlights, blower, A/C, etc. before starting and then start while monitoring the IAC target and actual. If the ECU does not raise the IAC in this case, then this could be the cause, i.e., problem alternator or current sensor. The ECU should open the IAC considerably under this condition regardless of how it determines the engine load. Then again, it could be nearly every sensor on the vesicle and this idea/guess, could be completely wrong. Mostly, just thinking out load with initial thoughts. One other thing would be, I think, to ask the customer if they are getting gas at a different gas station or something like that (maybe this new 15% ethanol gas that some stations have). I don't think this is a Flex Fuel vehicle, so the ECU may not know the alcohol level of the fuel and therefore this may be irrelevant. Again, a very interesting case.And, thank you for taking the time and putting in all the extra work to make this video for everybody.

[@nickmalone3143]

Damn ethanol ...."for the environment" but pollutes more and less milage than gas ... our geniuses in state legislators and in congress

[@mikechiodetti4482]

I'd start with that battery! I once had a tps on an older Dodge Van cause the AIS motor to move intermittently with just off idle slow throttle movement. New tps fixed the problem.

[@dwaynemedlin8683]

Windings in a coil that shorts out when hot changing the path and resistance, confusing the pcm. That maybe,and it’s a custom van. Often I have seen have a next year update than the stated year.

[@inothome]

TPS, idle relearn and address the slow, hot cranking. The TPS and throttle position looked funky, but also not there in person pressing pedals......

[@elchefe7701]

Is the endpoint-calibration switch of the the stepper motor o.k.?

[@MrBorntoroll]

Great case! As always! Does it have EGR? Maybe it is not closing , map sensor reports incorrectly and IAC closes to correct?

[@AlexHernandez-sc4vg]

EGR, another usual suspect Def worth a look

[@calholli]

2mins in, sounds like a IAC sticking if it has one. Or could be a purge valve.. But those should throw codes. So this could be interesting.

[@huntnfishnuts5880]

The IAC motor can get carbon fouled on these, the jeep 4.0 engines where more common with the hot soak no start. They had a TSB for that to install insulators on the injectors. If the 360 looses battery voltage it will reset the idle memory and want to stall. Starter sounded like if was laboring to crank it over??

[@Nikoshasib]

I am still thinking coolant temp sensor or MAP sensor. If your coolant temp reads incorrectly it may cause the ECU to tell the IAC to do weird things when warm. Also if your MAP was reading incorrectly or dropping out you might have a situation where the ECU doesn't tell the IAC to do the right thing. The IAC isn't an input in this equation but an output. What signals does the ECU make it's decisions on to command IAC? TPS, coolant temp, MAP?

[@AlexHernandez-sc4vg]

W/o watching part 2, My guess is MAP. The IAC appears to operate perfectly

[@anthonygrant317]

I agree with everyone else, either the PCM info input is corrupt or its response. Nice case.

[@brianknight6661]

Also, have seen EGR valve stick on those motors.

[@citichap]

I have a 97' Dodge Ram van with the 3.9L engine. I had almost the same problem, found loose hose lines going to the charcoal canister under the right side of the van. Put hose clamps on to fix it.

[@scientist100]

That will not cause this issue as the purge valve is normally closed so it cant vacuum air in. All the charcoal does it trap fuel fumes and then the PCM commands the vent valve to close and open the purge valve to absorb those fumes into the intake manifold when the pressure is high. Normally you could have the charcoal removed and vent the fumes into the atmosphere and will not cause any issue except when the monitoring occurs which is what I described and will set a large gross leak code. The purge valve may never be commanded open if the fuel tank pressure is always atmospheric pressure and some cars will set a code also at the fuel tank pressure sensor.

[@mikeafa1]

Is the KZbin plaque on the wall new? For 150k subscribers? If so congrats to a fine car surgen.:)

[@TheWaelabo02]

Sound to me dumping gas to intake through Purge Solonid or injection system if run rich after starting. But if not run rich , I have to check 5volt signal and cmp & ckp sensor signal. I will keep watch now and see what happens . Than you .

[@jimforsyth2.]

those old chryslers had a problem with it iac resetting with a dead battery or replacment . the throttle body gets dirty and it doesn't comp thinking it's clean . trying to return to 13 steps with a good clean blade gap. stall on decell and start up

[@joshboyer8449]

Have you inspected the throttle body yet? If not check the TB and clean, if nothing changes a clean TB will only help. Hope that helps

[@danielkearns3600]

Start simple especially with noticeable slow cranking especially if there going on a trip and failing to start later. Test battery, starter possible voltage surge enough that it loses iac learned values. Would clean tbi and if replacing iac do not use aftermarket parts have had these issues years ago after trying to save money on iac motors. Would do hard reset if cleaning and replacing iac by disconnecting battery and turning headlights on to pull capacitors in computer to clear any learned values and test drive above 30 mph.

[@10100rsn]

PCM may have a dying capacitor, MOSFET, IGBT or a bad connection somewhere. If it is the old style tin can JTEC computer then you'll get some stuttering at lower speeds or when you hit bumps because the older PCM has a daughter board with a connector that comes loose and many other problems that creep up with age. Sometimes you can cure the problem by backing out the lefthand screw on the front plate and cause it to stall by touching the same screw... This is never the connectors on the harness like some may think, it is the PCM side when its the old tin can JTEC computer...

[@jessicav2031]

One possible reason I can think that the computer might drop IAC is if it thought the throttle was not being pressed. Perhaps there is something weird with TPS that caused the computer's learned idle threshold to be too high? In that case, pushing the throttle would raise RPM but since the computer still thinks it is idling, it would drop the counts to try to maintain the lower RPM. I would investigate the TPS signal for an intermittent fault.

[@mikefoehr235]

Interesting theory. Does this van have throttle by wire...I think it is too old for that.

[@jessicav2031]

@@mikefoehr235 If it did, it wouldn't have an IAC right? :)

[@Dtapia63]

@@jessicav2031 💯

[@maintenanceman1015]

I think you right those systems have a tps they get hot spots on them . Others thought powers and grounds dodge has terrible grounds

[@davidturner4639]

TPS showed plausible numbers on the scanner but that's an average. I think the TPS has some bad spots in it.

[@billmoore6520]

Have seen a lot of floating throttle position sensors causing a similar issue on dodges. Tap on the tps while watching the voltage on the sensor, it will not usually set codes.

[@scowell]

TPS my guess also.

[@jwray9799]

MAS sensor...readings are temp dependent and will effect AF mix, delayed by the air horn length. IAC will try to compensate but the delay causes over shoot..

[@vapecatt]

I've had this kind of issue on GM products for some unknown reason. It's very random. I always thought of it as I had to make it relearn. I still have no clue why it occurs.

[@stevetaylor2445]

Seems like it needs the minimum idle setting adjusted similar to obd1 gm vehicles? Should TPS not be .5v?

[@dtls6353]

My guess would be an out of spec IAT, and heat soak on top of that. what would be fuel trims before the soak and after? 🤔

[@franksprecisionguesswork501]

I think you proved the iac is working (mechanically)perfectly. So why is the ECU commanding a low position? My guess is incorrect sensor feedback. I’d check temperature sensor, tps and tps position calibration . You didn’t show fuel trims during the symptoms, but My guess is they are nominal. We know the ECM has no actual feedback so in has to go through a calibration process some time in the scheme of things. I don’t know if it’s a one time operation at start or periodically during a time when the engine is part throttle an not expected to idle. It’s not attempting to increase the idle because it’s not trying to open the iac so I think it’s trying to calibrate but then again maybe you need a new flux capacitor!

[@billmonroe8826]

Always start with a good battery. It seems this one shows signs of weakness so before I go any farther, I'm checking that first before I scratch my head more. lol Too bad that Snap-on Verus is so pricey!

[@PineHollowAutoDiagnostics]

You can get one on eBay for not too much...but maybe Bidenflation has changed that lol

[@billmonroe8826]

@@PineHollowAutoDiagnostics Don't you be condemning that Russian agent, Ivan. lol

[@stigonutube]

non genuine iac control valve is my guess, bought a few cheap non oem in past recently and they look the part but just does not work as good as OEM and yes was 30bux vs $300 OEM mitsubishi.

[@edwinlomonaco6754]

My off the cuff guess would be iac or egr. Both could get stuck once engine is at operating temperature. We'll see. Part 1 here we go.

[@stevewalker412]

Magnums dont have egr

[@fredwalker839]

For what this is worth,,, in the early TBI days with GM ( same theory) I replaced many IAC ‘s , cleaning worked most of the time, carbon on it’s seat makes the 12v stepper trying to compensate , gets them “hot” & not doing what the pcm is telling it to do! Just think, that stepper is running constantly & like you and me, we get “tired!”OEM only, no “slant eye crap ! LOL & clean plates

[@Super8_150]

Hate to break it to you, but every dealer has their parts department shelves filled with "OEM made in China" parts. US buyers want cheap and no pollution here. China has plenty of cheap labor and could care less about environmental stuff pumped out of their factories.

[@williamnordin7976]

I've had a similar issue with a 91 mustang gt and an 01 explorer sport trac. I could drive them all day long. The second I'd turn them off they won't start for 45min. Turns out the place I was getting gas at was killing my fuel pumps. They wouldn't come on when I'd try and restart until they cooled off. The explorer was under warranty. I explained what it was doing. The next day they said it was ready and there was nothing wrong with it. I picked it up and drove it for a while then went back and turned it off. Made the dude come try and start it. It wouldn't start so I asked him if there was really nothing wrong with it?

[@CodycoWeb]

Back to basics, fuel injected engines like these all flare when started. When you start them the rpm’s should flare to like 1100 rpm’s then drop back to base idle. Hot or cold they all flare. This engine isn’t doing that. This needs to be fixed before attempting to diagnose any issues. Clean bore and the IAC to get this working. The steps is a learned value from where the motor stops after seating and backing out a given duty cycle command. Also the starter draw sounds like it may be resetting the learned idle control. Check the basics and fix the idle flare issue and check battery voltage during cranking.

[@TheWaelabo02]

Map , tps and coolant sensor were basic sensors input to control IAC. Before go deep mack sure alternator change Good , sensor ground and 5vol reference ok .

[@abdouallahuniverse5689]

That RPM 640 wories me, it is too low, it should be more than that,and 90 percent IAC commade also a problem too much IAC command at idle, it may need minimum idle adjustment to spect, with IAC and purge valve disconnected, like honda CRV 99, no one know about mimimum idle with IAC and PUrge valve disconnected . till i found it on the repair book bought from autoparts store autozone, and when i checked the minimum idle, i found it too low like 420, and it should be 480, i turned the adjustment screw till it get to 480, and then connected back the IAC and purge vlave, and cleared DTC codes and my idle problem, fixed, it should be different procesure for that kind of car, but since it has throttle cable and IAC, then there is a minimum idle adjustment with IAC and purge vlave disconnected. But first you need to check and clean the throttle body and IAC from any carbon deposit.