Foxbody surging idle/hard start when Hot - Part 2

[@9011combo]

Man.. i got the same problem with my car..been watching you now..

[@thefoxlife3431]

Thanks for watching. I ended up with 6 videos on my starting issue. It’s finally fixed. 👍

[@dougfoster8809]

Have a 92 GT, does the same thing, was thinking computer was drove enough to keep everything in check. since then problem has not been as bad every 5 drives it does it, shot in the dark, rooting for you too! driving helped mine alot!

[@dank8846]

I'm rooting for you to find something, as I'm having a similar issue. If I have to do a hot start, I have to rev it up as I'm starting it to get it to run. It will also RPM "hunt" for a few seconds, but then run fine after that.

[@thefoxlife3431]

Good luck. I’ll keep everyone posted on my progress. Sounds just like my issue also.

[@stenjohnson6149]

Me too!

[@bobs.3346]

Not too sure if you figured out the hot start issue. I had the same scenario, cold start no problem, run for 10 minutes then shut it off, no start but cranked no problem. Strong smell of fuel, injectors pulsing, good spark but won't fire. Replaced TPS, ignition switch, distributor, TFI module, cap, rotors, wires, spark plugs. All parts from Ford other than the distributor which is from MSD. As mentioned cold start no problemo, hot start no fire. Turns out it was a burnt trace on the underside of the computer which I viewed with a magnifying glass, pin 46 I believe. Local computer shop made the repair and now it starts hot with zero issues. Hope this helps someone else out and I do have pictures if required.

[@thefoxlife3431]

Thanks for the info. I did have my computer rebuilt over the winter and this issue started a few months later. I originally thought my computer was causing another issue where my car would die while running. That ended up being a bad PIP sensor in the distributor. I may have to send the computer back if I don’t get this figured out.

[@bobs.3346]

@@thefoxlife3431 It definitely put my troubleshooting skills to the test. I didn't catch the computer issue first time I removed it as I only took the cover off of it. Second time around I took the cover off and removed the circuit board from the metal base that it was attached to. The burnt trace was on the underside of the circuit board and not on the top side. I did take pics that I can forward to you if you're interested.

[@AwakeDude911]

same here looks like my 87 gt when i try to fire it up ....stared at the basics..... grounds, smoke ,fuse able links piston psi check.....found out my coolant temp sensor and spout connecter was getting under a volt 0.63v when they should getting more volts (TPS was getting the 5 volts) so i think i have a Boken wire in the harness or a mouse chewed some wires ..waiting on a new harness as the computer was rebuilt last month by ecu repair in Florida....

[@thefoxlife3431]

Finding these gremlins is frustrating. I’ve also had my computer freshly rebuilt and tested by FoxResto. It ran great after that, until this issue pooped up. It sound like we’ve done a lot of similar things. You could also check your salt and pepper shaker connectors. I cleaned mine and opened up the male terminals a little to get better connections. Good luck.

[@EASTCOASTIMPERIAL]

What instrument cluster is that? Yooo, your ride is clean FRFR!!!! 💯 🎉

[@89gt5.0]

So i had a similar issue not long ago. It’s worth checking. Mine would start fine at times and then start and die instantly. I didn’t think about it at the time but i also had the bbk fender well kit and got tired of the way it looked so i put the stock air box on with a new filter and issue was resolved. The filter was plugged up but it didn’t look that bad

[@thefoxlife3431]

Thanks for the info. I’ll check the filter and MAF but they were replaced in 2020 and I only drive it about 500-800 miles a year. I wouldn’t think it’s plugged. But you never know.

[@nashhernandez461]

If no Fuel presure check the small hose in the Fuel pump

[@gx21a]

Sorry for the wall of text. TL;DR- I had a similar symptom due to a loose TFI connector, check out that wiring. Troubleshooting suggestions for fuel or spark to help with what to focus on. I had similar symptoms when I accidentally jostled the TFI connector loose (not completely, but barely making contact) when I was working on something else. I only found out that was the cause when I accidentally bumped into it again as I was troubleshooting. I am sure your cause is not exactly the same since you swapped TFIs (and I am sure you snugly connected them), but symptoms are similar, making me suggest that you look at the wiring going to/from the TFI. For reference, here is what plugs into the TFI: from top to bottom, 1- PIP out, 2- SPOUT in, 3- START SIGNAL in, 4- RUN POWER in, 5- COIL NEGATIVE, 6- IGNITION GROUND. If you did not already know about it, I also suggest you google 'veryuseful(dot)com fox mustang' (not sure if YT would block urls) and take a look at the wiring diagrams which might help with the troubleshooting. ScannerDanner also had a good video on Ford EEC-IV No Spark Diagnostics on a Bronco. With key on -running or not-, you should be able to get spark. You mentioned fuel pump, but before you swap that, check that the pump functions and is getting power and is building pressure. First, you should hear it (it's getting that initial power), which I could in your video. You can remove a spark plug and crank (keep area ventilated and unplug coil first!) and you should expect to smell fuel. Test pump wiring upto and past the relay. Questions to ask- does your car have anti-theft or any other device that may be in between any signaling for ignition? Check the safety switch that prevents start up if the clutch isn't depressed (neutral gear switch and I think this would prevent the starter from even engaging if it was bad)? For testing the MAF, just unplug it, the ECU will use predetermined values. Don't worry man, a lot of us have been where you are and I hate to see you throw away money to replace something that may have nothing to do with your issue. Granted, you did need a FPR replacement. Other ideas (or blind stabs)- Engine Coolant Temperature sensor. Not to be confused with the sending unti that goes to the gauge cluster. Maybe PIP (although your distributor looks fairly new). Some folks may try to also pin it on the ECU... but try everything else first before you consider that. Just make sure its ground look good. Verify normal/abnormal conditions before you start it up and when it gets hot and not starting. What do the voltages look like. Again, sorry about this short novel. And even if I am dead wrong about the cause or what tests I suggested (I am in no way an expert or a certified mechanic), I hope I at least get you in the right direction and wish you good luck in determining the cause and fixing it.

[@migismalls4862]

If it wasn’t for that only happening when hot. I would have suggested it could be your ignition switch connector (wires on column not the tumbler for your keys). They have a tendency of separating and don’t let the car stay on.

[@thefoxlife3431]

Yeah, I had the ignition switch in the column go out last year. It would shut off while driving. That’s at least one thing that I don’t have to worry about.

[@think1stproductions]

The TFI MODULE will do that after it gets warmed up to operating Temps etc. The fuel pressure shouldn't dip on revving up.

[@xstreetracer3474]

Next time it happens try cycling the ignition 4 or 5 times on the 5th cycle try starting the engine. if the engine starts and runs then most likely the fuel pump is the problem... another way to get an idea as to whether or not you're having a fueling issue is to ask a friend to watch your fuel gauge when you try to start the car.. good luck god bless

[@rolandtamaccio3285]

@600wheel , how you been ? ,,, I know these injectors can clogg , but are they known to leak ? Running very rich and surging , fuel mileage is atrocious. There's a whole list of things I have eliminated . Just trying to decide whether to clean my injectors or replace them . Originals with 120 thou on them . Engine is untouched original in '91 Mark VII . It's definitely not the pressue or regulator , or leaking reg . I run a pressure gauge full time . Also check TPS parked and running with volt meter taped to windshield ,,, !

[@eddymac2052]

Had the exact problem with mines for months, really annoying. Timing was too high also had to adjust throttle screw and tps sensor. Starts every time now and idels smooth

[@plumbbob3778]

I'm having the exact same problem. Had my ECM repaired (all capacitors replaced) and circuits inspected as it was only producing 4V to the fuel pump instead of 12V. I also changed fuel filter and TFI module with no improvement same as you. Have you pulled your ECM and looked it over? I will post my results after I put the A3M back in. My car is a 1993 coupe currently using an A9L I bought used to try and fix a problem with it shutting off while driving. I suspect the A9L has issues so I'll have it fixed as a spare and run the A3M I just had fixed. Thank you for the excellent videos, you have WAY MORE patience than I have. Hopefully this will fix my problem, and if it does probably your problem too. Fingers crossed...

[@s3w349]

Please understand I am not criticizing. You need to watch some Pine Hollow auto and or South Main Auto videos. They don’t typically work on older cars but they both go through a lot of crank no start videos without using the parts cannon. Definitely one thing I’ve learned is because it’s a new part doesn’t mean it is working properly ( or at all ) good luck

[@thefoxlife3431]

Thanks for the info. I’ve not heard of either of this channels. I mostly look for Fox specific examples in my searches but have started branching out on this issue. My investigation has definitely allowed me to find a couple issues, such as the leaking FPR. I just haven’t found the no-start when hot cause. I hate the fact that new parts I installed within the past year could be the cause of this and you can’t assume a new part is good.

[@s3w349]

@@thefoxlife3431in other car videos I’ve seen the coil can be the culprit. Yes even new ones( China crap ) ignition module or actual ignition switch on the steering column. Not sure everything you have checked. I watch a video foxbody704 I believe and he goes to a guy that works on foxes I think exclusively it may be worth getting in contact with him. I’ll have a look for the video

[@s3w349]

My apologies wrong name. GearHead704. Under the heading Everything with my 4eye

[@thefoxlife3431]

I have had a few suggestions to look at the coil and it is brand new so it could be related. I didn’t have this issue before I purchased the ignition kit with a new distributor, coil, TFI and wires. I had a bad PIP in my factory distributor so I bought the kit. have swapped the TFI with one that I already had and it didn’t help. I’ll try the same with the coil that I removed. Thanks for the support.

[@thefoxlife3431]

I know that channel and the shop he uses a lot is Fox Resto. I sent my computer to him for a capacitor replacement and bench test of all the circuits. He’s got a lot of knowledge for sure.

[@xstreetracer3474]

If you already verified that you have good fuel pressure (at the time of no start) then I'd suggest you look towards the Distributor module. it is possible that the module maybe overheating causing a no start once the engine is hot

[@thefoxlife3431]

I’m still diving into the fuel pressure side of things. I’ve never really watched it that close before so I’m not sure what “normal” really is. I recorded the gauge when starting and it jumps to 40psi and then instantly goes to 20psi before I try to start it.. I’m thinking the fuel pump has an issue because it also looses pressure very quickly after I shut the engine off.

[@xstreetracer3474]

@@thefoxlife3431 That definitely sounds like a fueling problem. I doubt that it's a stuck open injector But it wouldn't hurt to pull the dip stick and check the oil for fuel. going by your description it's most likely the fuel pump. you shouldn't be having excessive fuel pressure drop off like that.

[@Roc900]

Nice Build… What Front Spitter do you have?

[@thefoxlife3431]

Hi, thanks. The splitter is from @makersgarage.

[@richardmikolajczakjr5016]

Check resistance of the coolant temp sensor cold and then recheck after it warms up possibly sensor is out of range and computer is thinking engine is cold and giving same amount of fuel on a hot restart?? Do you have spark when this happens hall affect sensor in distributer could be dropping out after a hot soak.. also unplug your mass air flow sensor I’ve seen these cause many no start issues on the early fords

[@jeremycopeland3835]

Had the same problem. I had a ready to run distributor and water got in to it and caused some corrosion. Everyday it started once a day.

[@MarkJackson-b7g]

Love the video , Man . Make sure when you install a new part .that the part is good . I don't know how many new parts I have gotten for my 91 Mustang and the new part was no good . O and you will get it . I think that you just have 3 things wrong with your mustang . You found 2 .

[@thefoxlife3431]

Yeah, it definitely seems so be combo of sudden issues. I don’t believe in coincidence so Im trying to find a connection to all of the issues. More to come.

[@awhitness]

When your car is idling and you disconnect the IAC what happens? If it dies adjust the throttle until it will stay running and reconnect the IAC. Also have you checked vacumme with a vac gauge? (Check when cold and hot)

[@thefoxlife3431]

When this first started to occur, I checked timing, unplugged IAC and adjusted idle to 700rpm, adjusted TPS to 0.97ish and then turned off the car and plugged the IAC back in. I unhooked the battery for about 30 minutes and then did a base idle reset. By the time I am ready to do the second 2 min run under load, it usually takes a few tries to get it started. It will run just fine with the IAC unplugged, if it’s not already hot.

[@awhitness]

​@@thefoxlife3431 Have you had a chance to check your vacuum? Sorry if Im saying something already checked. I just recently struggled with an 88 GT. Checked vaccum and it was only 11hg. turned out to have 2 very small vacuum leaks in the smog evap EGR system. gave me fits. Also I would focus on when it started to act up, and what work or change was made on the car. Wish the best.

[@robhunter2435]

Check your fuel injectors, make sure they are not leaking , Even one can cause a flood condition and create a hard start when hot. When the engine is cold the fuel in the intake has evaporated overnight allowing the car to start but once started the injector leaks fuel into a hot engine flooding it. Your fuel pressure drops too fast indicating a leak. Pressure should stay at high 30s for at least a minute and very slowly drop.

[@thefoxlife3431]

Yeah, I’m going to look at them more closely. I think the fuel pressure drop is too fast to be a fuel injector. It would have to be pouring out because my pressure goes from 40 to 0 in about a minute. I already changed the fuel pump and it didn’t help. I’ve removed the injectors, 4 at a time, from the lower intake manifold and didn’t see any leaks when I cycled the key a few times.

[@winstonfortin237]

Hi...just passed over your 2 videos... You show every time start up, warm up and then shut off. After a short while you will try to start up with no luck.....but how is the driving experience....does it drive well with good power ?? Will the engine stay one without dying at any moment ?? Incase you have any ignition upgrade like ignition box or even coil upgrade....I would say go completaly back to stock and see what happens. Those ignitions systems are known to suddenly start working bad. Had 2 times bad experience with this. Hope my suggestion might be your problem solver , good luck

[@holmesteang3152]

I'm going through the same thing bro pulling my hair out on my foxbody. Parts after parts after parts I'm running out of ideas smh

[@murphyslaw5.095]

Have you checked the idle air control valve or the MAF?

[@thefoxlife3431]

Thanks for the message. I did swap the IAC with no effect. I’m going to look at the MAF based on your comment and a few others.

[@richardmikolajczakjr5016]

Also check all your 5volt ref circuits and see if any of the sensors are pulling down the circuit make sure you 5 volt ref isn’t getting lost coming out of the computer itself Also a faulty baro sensor will do this

[@jaydenharvey723]

I’m chasing this same problem on a fresh 4 to 8 swap

[@thefoxlife3431]

If you figure it out, let me know. I’ll do the same. Good luck with the build.

[@jr79841]

I recently had a similar problem, it ended up being a distributor despite being new

[@thefoxlife3431]

I have another one on the way. I’ve got a couple more ideas to try before I open it. Hopefully I can return it and not worry about it soon. 👍

[@fpvjt146]

Take your fuel cap of on a hot start. See how much vaccum comes out. Your fuel pump might be fighting itself if you have your EGR capped off.

[@thefoxlife3431]

Thanks for the suggestion. That is something I hadn’t thought of yet and will give it a try. More to come.

[@christophergriffin8344]

Do you have a different mass air flow meter to try?

[@thefoxlife3431]

I don’t have a spare but I’m going to remove it and take a look at the sensor. It was replaced in 2020 and only gets driven a few hundred miles a year so I hope it’s Ok.

[@neilleavell]

So where's part 3 at did you get it back to running or what?

[@thefoxlife3431]

Part three is out and I’m getting closer.

[@1calvin]

I noticed your CEL light doesn't come on... JMO unplug the mass air and see if it starts (goodluck)

[@thefoxlife3431]

I’m not 100% but I’ve seen several videos that talk about ‘87-‘88 V8 cars didn’t have a CEL. The bulb wasn’t even added to the gauge cluster. 🤷‍♂️

[@rolandtamaccio3285]

Will somebody please explain to me why Ford didn't just regulate air/fuel with pulse width , without all that vacuum b.s. ,,, ? ,,, btw , will a regulator cause a '91 5 liter to not run at all , or just barely ,,, ? ,,, It's not the ignition runs fine on starting fluid ,,, !

[@rolandtamaccio3285]

Evidently it was necessary or financially expedient to do it this way because GM also has something similar ,,, ?

[@bassplayer426]

My issues turned out to be the ECU needing rebuilt.

[@thefoxlife3431]

Where your symptoms like mine? Would it start and run just fine when it was cold but not want to start anytime after that? I had my computer rebuilt a few months before this issue started. I guess it could be the issue though.

[@dentonpage3802]

Change the spark plugs, they are so fouled from the leaking regulator.

[@thefoxlife3431]

Yeah, I replaced them as soon as I saw what the old ones looked like. It hasn’t helped my no-start when hot issue but it was definitely needed.

[@ZR1VengefulMMAGTS]

I had similar issue on a vehicle after chasing it for weeks turned out to be fuel pump check valve leaking back into tank causing fuel to vaporize / vapor lock in rail and cause no start / rough start and idle.

[@thefoxlife3431]

I’ve ordered a pump to have ready in case it goes out. My plan is to look around the tank and see if anything looks odd. My fuel level gauge seems to have stopped now also. 🤷‍♂️

[@ZR1VengefulMMAGTS]

@@thefoxlife3431 good deal! I started changing lots of parts to upgrade however last item was fuel pump and that solved everything hopefully it gets dialed in nothing more annoying than chasing problems down however you seem to have good mechanical knowledge you will get it all sorted out!

[@kelsoc5222]

Fuel pump problem.

[@evielknievel4972]

Fuel filter.

[@ecc5119]

Change the timing chain.

[@smashyaface349]

just sell the car to me and stop worrying about it!

[@thefoxlife3431]

Ha, I’ve been cursing her enough lately that I’ve threatened to sell her. 😳

[@EASTCOASTIMPERIAL]

Lol

[@RedHammerBodyShop]

First off stop just letting go of the key and letting it snap back. Lol Jesus