Stop the surge! How to PROPERLY set the idle on an 89-93 Foxbody Mustang.

[@Riffs_Garage]

Finally, someone who shows the right procedure for an idle reset. The only advice I would offer is disconnecting the tps while performing the base idle reset. I've learned through tuning these cars that tps voltage is a myth. There's a wide range that the voltage can be set in. I think it's .70v-1.2v, and it'll be fine. The reason the .98v was thrown out there is because it's in the middle of that range. There's nothing wrong with setting the voltage to .98v just not necessary. Also, for those curious what SPOUT stands for. (SP)OUT= SPARK OUTPUT. Good video explaining how idle works and how timing directly affects idle.

[@happygilmore8768]

0.98volts is the actual setting Ford used at the factory to make all of the engine settings when tuning the ECU...Ever heard of a thing called " Engine Load"? Engine load dictates how an A9L reads and alters the tune numbers...Its done using complicated math inside the processor and the settings set inside the ECU gives it a preset operating range or voltage value , frequency range , degrees or even time setting for each sector .. Theres this lil thing called a checksum setting that the computer auto generates after doing a calculation of all the internal settings as a whole and the ECU verifies the current state against this checksum number..... Any changes made to an ECU via a tuning chip alters this checksum value number which gives the ECU a different outlook on the state of the current combo..... If the checksum number the computer is sensing doesnt match Fords number the computer doesnt do accurate calculations as per the combo................... A stock checksum number for a stock Mustang 5.0 Five speed car is 60638 and the computer follows what the boundries of the checksum dictates..Dropping the TPS voltage without making appropriate changes in the TPS scaling tables drops the engine load calculation number and throws off injector timing calculations aswell as where the engine runs on the spark also injector timing table and once you go beyond the 12% adjustability youre running dangerous..... If you change the combo in any way from bone stock you must update the internal settings inside the ECU which gives a new checksum number which is done with a tuning chip or even a StarTool used by Ford... My new checksum number is 6861 and must be noted for when i need my ECU repaired or reflashed or ill get the stock 60638 reinstalled...... What most dont realize is if you had a Ford Dealership thats known for performance vehicles like Crown Vics & Mustangs that had the $3300.00 StarTool youll find that they offered a progressive tune package where they finetune the tune on your vehicle as per current altitude , engine state and MAF Flow etc which gives the ECU a new checksum number especially If you paid for this service after installing Fords preformance accesories like camshaft headders etc you were given the info for ECU repairmen to verify or like stated above it will yield in you getting a stock checksum in return.........Its the same ECU tune they do on all police cars too but that wasnt ever discussed and also to mention that when copcars are sold at auction the ECUs are supposed to be reflashed with the stock checksum number and speed limiters...LOL kzbin.info/www/bejne/n6S8mpWwbMeqqZI

[@austinjames3525]

So glad you’ve posted this video. I was battling my 95 GTs surging idle before it blew the head gaskets in 2022. I’m rebuilding the 302 as a 306 and hope to make these changes when it goes back together soon!

[@BrandonKnight-il9xs]

Did u fix urs? My 88 blew something I'm not sure yet I just know so far k-seal sealed whatever it was up

[@happygilmore8768]

Blew the headgaskets you say?...Thats what happens when you change the engine combo and still have the stock checksum setting inside the ECU...When you change engine load and dont make appropraite changes things like blown headgaskets happen when you are operating in a lower load range with a higher spark advance... My advuce would be to get a tuning chip and follow the tutorials by Leech tuning as hes the closest guy on the internet to giving the real poop about how the A9L really works and how to make the appropriate tune changes as the combo changes so the ECU's processor can process the right checksum number.... kzbin.info/www/bejne/n6S8mpWwbMeqqZI

[@dannyingamells6642]

Hi, Joe- just got my new, new new INNOVA timing light with the built in tach. Word of confession here...I'm working on a Cal 88 thunderbird with 5.0 engine. ALL STOCK. My car does not come with the sensor you have on yours that runs through the air intake (MAS air sensor). Going to take your advice and hook up and check the timing with spout disconnected to verify 10° and do the idle stopper screw with IAC disconnected to 750. After adjustments are made, turn off car and replace spout and IAC and I should hopefully stop the surge!

[@thisisyourcaptainspeaking2259]

Did these throttle bodies have a mystery teflon coating around/on the butterfly that's likely long gone after all these years?

[@imacarguy27]

This is extremely helpful. Going to give this a go tomorrow. Installed my cam in October and still havent gotten it exactly how i want it. Once you plugged your IAC and timing spout back in, did you do the base idle reset procedure when you run it with loads off for 2 mins, shut the car off for 2 mins and then run it with electrical/hvac loads on for 2 mins?

[@fu1543]

That to I'd like to know

[@brandonknight7240]

Very similar to my 89 build, i built mine into a 331 scat stroker with a trickflow top end kit 170 heads stage 1 cam holley systemax upper and lower, mine had mac shorty headers also and at that point during breakin it did great, had stock distributor and throttle body, the issues showed up after a bbk 75mm throttle body and bbk 1-3/4 longtube install, i have a dead cylinder i think so i just got everything to upgrade the fuel and fire componets - procomp distributor and msd coil and adjustable fuel regulater also high dollar 24lb injectors with motorcraft o2 sensors and the correct o2 extension wires, i made the ones on it now, hope all this stuff helps

[@Jack-q4o]

Excellent ! Chasing surge for a decade. How did we Bravo Joenot think that yes the computer is adjusting timing as we are adjusting idle screw

[@DilutionDavid]

Thanks I will try that I was just removing iac I still couldn’t get the car below 1000 rpm’s without shutting off. I will try your way and see what happens thanks

[@kevinsmith-wd1zj]

Did this work for you?

[@Joesmusclecargarage]

@kevinsmith-wd1zj Of course. It has worked on every Fox I have touched.

[@engabdulsalam11]

⁠@@Joesmusclecargaragedid you disconnect these while the car running and then connect them after adjusting the idle screw also when the car running? Thank you

[@Joesmusclecargarage]

@engabdulsalam11 Disconnect the IAC and SPOUT before starting the car.

[@larrywizorek5006]

Thank you for this information. I have a 93 Hatchback with a 331 trackheat heads and intake with a Comp Cams 276H-R14 cam. This procedure worked very well for the most part. Once the car is up to temp and it is shut off, it will not idle. It has a giant surge or two and stalls. It does seem easier to catch it with the throttle now. It is idling at around 850 rpm. If you have any suggestions, they would be greatly appreciated. Thank you. Larry W.

[@dannyingamells6642]

Joe, thanks again for your advice. My issue starts when I start the car, which starts fine. As you know, when you start the car, it runs a little rich for a while, then leans out for the fuel econo my. On either a hot or cold start, when the leaning begins, it surges and loses power. It won't shift (automatic) unless you put the pedal to the floor and it shifts hard and could damage the trans. If I disconnect the EGR hose to the diaphragm, this issue is greatly reduced to a point where you can drive the car without pulling over and waiting 30 to 45 seconds for this terrible condition to stop. After 30 or 45 seconds of hell, the computer adjusts the issue and the vehicle drives normally until I start the car again. I don't like driving with the EGR disconnected because the vehicle is not tuned for it, and I do not know a hot dog tuner in Cal that will delete the process from my ECM. I have replaced the CAT, tune-up, and all the EGR components including the brittle plastic tubing. The fuel pump was replaced a few years back, and it has no trouble starting. I have a new fuel pump relay but again, she starts fine. Replaced the PCV and the nasty screen below it. No check engine light, and the vehicle is an 88 which is OBD 1. I bought the car with a cold air intake and when the condition started I was able to find the original airbox off an 86 Mustang and verified it was the correct part. The thing is, when I tried to do a base idle reset I followed Brew2L advice and did not have a tach, and just did the reset "by ear." I would replace the o2 sensors, but no Check engine light. I'm getting my new timing light with the built-in tach tomorrow from Amazon and I'm going to give your solution a shot. I figured if the base idle was set too low the "lean episode" which might be a normal thing for the ECM, might be my problem. The fact I was only disconnecting the IAC and not the spout should make a difference, because all my "former adjustments" would just return to the same state after stopping the car. Thanks again for the great informative content, for answering my questions, and if you have ever encountered a vehicle that shows my symptoms and you were able to solve it, love to hear it.

[@NoLimitRacing100]

Thanks alot been having idle issues for awhile now never could find out why and what was going on till I watched your video

[@snowcat2178]

Hey! When you did all that you said in the video did you adjust the tps sensor with the volt meter? Thanks in advance. My 88’ gt is surging pretty bad especially when it’s cold.

[@Joesmusclecargarage]

Yes. Any time the minimum air screw on the TB is touched, the TPS needs to be reset.

[@snowcat2178]

@@Joesmusclecargarage ok great thanks for the quick reply. Hopefully if I have time tomorrow I can give it a try.

[@tylercapece138]

I used this method to adjust the idle on my 94 F-150 (same cam, but stock heads and intake) and at initial startup it runs fantastic, but now as soon as the speedometer senses movement the idle shoots up to 1,700 rpm...any ideas?

[@BigKidsRC]

Great tip on this I have an e cam in mine do you know what setting to set my timing ? Should I start with 10 degrees BTC and go up from there? Thankyou for the input 👊✌

[@JayVwantoC]

Thanks for the helpful video. I have a very similar engine setup except mine has a B303 cam with 75mm throttle body (placed in a 68 mustang). What did you have your initial timing set at? Or what should I be looking for when setting it?

[@Joesmusclecargarage]

My initial was at 16 degrees. Cams like the E,B, and TFS1 bleed off a lot of compression due to the overlap. I would put a vacuum gauge on it, start at 14 and see what it likes.

[@Jason-yv2bw]

For clarity, is this cold or at operating temp when doing this procedure ?

[@Joesmusclecargarage]

Operating temp

[@josecisneros2801]

Hi all, I’ve been setting my base idle in a different ways, some work better than others. I will use this method and see how stable my idle gets. I have that little plate in between the TB and the IAC. I guess I will combine a couple of methods adjusting the throttle stop to 0.010” + 1.5 turns with a feeler gauge and then adjust the air flow via the set screws on the throttle plate all of these wit that IAC and spout disconnected. Only one question do I have to disconnect the battery after all the adjustments were done for a computer reset, or it doesn’t matter???? Thanks for sharing👋🏻

[@Joesmusclecargarage]

@@josecisneros2801 The battery should be disconnected afterwards.

[@BrandonKnight-il9xs]

Mine is close, it's a 331 stroker trick flow 170 heads stage 1 cam holley upper and lower 75mm throttle body 24lb injectors and mine had Mac shorty headers but I convinced myself it needed more flow so I put bbk 1 - 3/4" longtubes and the sound isn't as good, shorties just sound way better, I'm thinking of putting dumps right at the ends of the mufflers but still keep tail pipes in place

[@djhotgq25]

Can you post the link of that plat you put on the Iac

[@Joesmusclecargarage]

@@djhotgq25 LMR sells them for $55.

[@DilutionDavid]

So did you fix it with the iac plate or remove iac wire and timing plug. I have the same problem right now and I’m losing my mine I can’t get it to idle below 1300 rpm’s. I checked everything. I have a 347 afr 185 head holy intake and Anderson 41 cam this is driving me crazy

[@Joesmusclecargarage]

I remove the adjustable IAC plate and set the idle with the IAC and the SPOUT disconnected. Get it to operating temperature, turn the car off, disconnect the IAC and SPOUT, set the idle as low as you can get it without dying out. Then shut the car off, plug everything back in and let the EEC learn and the IAC will control the idle speed. Try to get the RPM under 700 when you set it though. It’ll go up to around 850-900 on its own once it’s all said and done.

[@mattsgarage6385]

I have a 2001 cobra with stage 2 comp cams, intake, and full exhaust. She runs great except when I pull up to a red light and come to a full stop the engine fails to catch idle and the revs drop. Usually the revs fall to about 400 and then it recovers idle at 850. It starts up fine but when I rev the car from idle it always dies. The IAC and IAC wiring harness have all been replaced and the issue is unresolved. No one seems to know how to address the issue. Does this fix work with new edge cars as well? I've been having this issue for years and am dying to have a normal idle. Thanks man.

[@Joesmusclecargarage]

No. Only A9L and A9P cars.

[@therocket280z7]

The surge caused by the cam, that causes low idle vacuum like 10-12in, is because the cam doesn't have enough Lobe Separation Angle(LSA) for Fuel injection(FI). FI requires about 20in of idle vacuum to operate the Fuel Pressure Regulator properly. If it doesn't make enough vacuum at idle rpms to actuate the FPR, there will be around 20% too much fuel being put in, until enough rpms are hit to create at least 17-20in of vacuum. I'm not saying he's doing the idle procedure wrong at all. But, it would run as well as a stock motor if that cam had a few more degrees of LSA. Similar stock factory performance engines, with similar cam specs, run around 116-117 LSA so they can have 20in of vacuum at idle. I don't know why so many aftermarket cam companies haven't figured that out, but I assure you it's a wide spread problem...

[@Joeshomegarage]

Thanks for the video I just went through a mess trying to get my 88 supercharged notch to start. I set the idle at around 750 with the spout and iac unhooked. Shut the car off and plugged them back in and let it run for a bit. It's idling nice and smooth but staying right around 1k RPM. Should I do it again or is the iac off? I do have a 306, b cam, paxton supercharger not sure about the heads. Has a maf conversion too.

[@Joesmusclecargarage]

A B cam might like to idle at 1000, depending on the heads, compression, idle vacuum, etc. My TFS1 idled at around 900-950. Any lower and it would surge with the air on.

[@Joeshomegarage]

@@Joesmusclecargarage that makes sense. That's about where it idled when I bought it. I only drove it a few times then started fixing everything wrong with the car. It just wouldn't start last week so I ended up deleting the msd 6 al box, msd distributor and coil and just putting a new distributor in it. I think it was built 20 plus years ago and been sitting a long time. Thanks again 👍

[@GreenToFeelBlue]

So when do this, do you still unplug the battery like all the other places suggest? So the process would be, start car, get to operating temp, unplug iac and spout connector, set idle using idle stop screw, shut off car, unplug battery, reconnect everything, start car?

[@Joesmusclecargarage]

You got it 👍

[@GanjaSmoker-tk1xm]

​@@Joesmusclecargarageyeah but when would.you set tps I'm guessing after you have idle screw set?

[@kevinsmith-wd1zj]

Where does setting the TPS come in during this procedure? Also Accufab says not to adjust the stop screw as it is preset by them???

[@Joesmusclecargarage]

The TPS gets reset just like any base idle reset. Shoot for .090-.098 once minimum air is set. The factory TPS is technically “non adjustable”, but they have wiggle room. I always drill the holes a bit larger to allow movement.

[@dannyingamells6642]

Hi Joe...appreciate all your help. Okay, the Smog guy says my idle should be 850 RPM...so, grabbed a tach, as my thunder chicken did not come with one, and with spout and IAC disconnected, set my idle at around say...700 or 750, as after replacing spout and IAC plug, the IAC will elevate the RPM to around 800 or 850, or should I adjust the RPM to directly 850? with IAC and SPOUT disconnected? Thanks in advance.

[@Joesmusclecargarage]

Set it to 700. The IAC should have full control of the idle speed.

[@kevinoutdoors8504]

Any tips for a 1988 with idle surge. It's a customer's car and I'm running out of ideas and hair lol. I see it has all kinds of trick flow accessories and even trick flow heads. I'm not sure what's on the inside and the customer has no idea as well.🤷🏻‍♂️🤷🏻‍♂️🤷🏻‍♂️

[@Joesmusclecargarage]

Is the car SD or MAF? The Commiefornia 88s were MAF. If the car has aftermarket heads, odds are it has a cam. SD cars don’t play well with modifications, and most people convert them to MAF. It’s an easy conversion and is much more forgiving.

[@jedk9523]

Will this work on a 5.8? I swaped a 5.8 from a 92 bronco into my 86 tbird a while ago and in park/N it runs around 2100 rpm. I have checked vacuum lines, tps, and iac.

[@Joesmusclecargarage]

Yes. The same basic idle reset procedure applies to all EEC-IV equipped vehicles

[@lintsausage]

Will this fix it running rich at idle? I installed a trick flow stage 1 cam and it runs and idles great just the richness at idle ive checked fuel pressure, adjusted tps, it was fine before I did the cam i dont get if.

[@Joesmusclecargarage]

Any aftermarket cam is going to smell fat at idle. The EEC is going to keep the A/F stoich, but the “richness” at idle is cause by the overlap of the cam.

[@ratrodo3113]

It still idle surges with the spout and iac disconnected. I’ve tested every sensor ran codes got computer refurbished. Previous owner said it has a b cam. Also have checked for vacuum leaks. Been chasing this problem for months. Iac adjuster plate is the only way to get it to run halfway decent.

[@Joesmusclecargarage]

How low are you able to get the idle with the IAC and SPOUT disconnected? What is your base timing at? The B cam isn’t a big cam. I just set one up in a buddy’s car a few weeks ago. Idles smooth as can be at 800rpm with no surge.

[@reeseb9768]

The problem with my 331 with e cam trick flow heads my car idles real high soon as I crank it and I can't get it to come down... any suggestions I'm not the most skilled diy mechanic but I listen well

[@fu1543]

So just to clarify, start car up get it to operating temp, pull iac and the spout connector set rpm turn car off reconnect everything and done? Then restart car

[@Joesmusclecargarage]

Pull the IAC and SPOUT before you fire it up. Set the idle, shut it off, then reconnect the IAC and SPOUT

[@fu1543]

So at the end of this I did the base idle reset and now its all good

[@thruitallauto2538]

So all your doing is unplugging the iac, and the distributor spout set your idle while running, then plug everything back in

[@Joesmusclecargarage]

Pretty much

[@Jack-q4o]

Fattfox makes a nice TFI relocation kit....that current on distribution TFI location wii as you probably know leave you stranded

[@sto1asgoetia600]

Do you have an actual video show how this is done, hell I'm right now trying to find the idle screw

[@Joesmusclecargarage]

No. The verbal instructions are simple enough to follow.

[@sto1asgoetia600]

What if the set screw is an Allen wrench type and the bolt is ceased? Should I hit it with a little penetrating oil? Cause I did the iac and spout disconnected and attempted to use the screw but it wouldn't budge And my fox is idling at 1100 pm just about

[@Joesmusclecargarage]

@sto1asgoetia600 Give it a shot

[@sto1asgoetia600]

Letting it sit now, I tried firing the car back up and now it's back below 1000rpm idle, also gonna leave it sit for now, my crank pulley is wobbling really bad and FedEx delayed my part till tomorrow, and it's going into the shop for a new tie rod, I don't wanna damage something in the engine

[@wades5thscaleforlife872]

What did you use for a cold air intake

[@Joesmusclecargarage]

@@wades5thscaleforlife872 The factory airbox with the silencer removed. That is more than adequate until you’re DEEP in the 11s.

[@dannyingamells6642]

Can this apply to an 88 Ford Thunderchicken with a 5.0 engine?

[@Joesmusclecargarage]

Yes

[@dcldrummer]

Will it work the same on a sn95?

[@SawyerFord13]

Would I set the idle speed in park or drive with e brake on? I have an automatic

[@Joesmusclecargarage]

Doesn’t matter

[@SawyerFord13]

@@Joesmusclecargarage when I go from park or neutral to drive the idle changes dramatically lower

[@Joesmusclecargarage]

@SawyerFord13 It’s supposed to. There’s a load.

[@SawyerFord13]

@@Joesmusclecargarage right so if I set my idle in drive as opposed to park that would change everything ?

[@Joesmusclecargarage]

@SawyerFord13 Set it in park like it’s supposed to be set. Set the idle where you want it, and factor in the RPM drop when it goes into gear.

[@cassandralesh8536]

It's in the factory service manual.

[@Joesmusclecargarage]

I’m well aware

[@rajsub5594]

Should show us idle with ac off

[@Joesmusclecargarage]

I dumped the car a month ago

[@andrewlopson3394]

​@@JoesmusclecargarageAfter all that work, you sold the car?...just got tired of it?

[@Joesmusclecargarage]

@@andrewlopson3394Yeah, I didn’t have much interest in it at all. That was my 6th fox mustang. Getting rid of that car gave me the space to finally paint and finish my LS swapped 67 Chevelle.

[@andrewlopson3394]

​@@Joesmusclecargarage Chevelle...Awesome!...I have a coworker with a '70 Chevelle--his pride and joy (might as well be a part of his family)...with a worked over 400 big block and exhaust valve for the optional wide open effect...it lives down stairs in his man cave with his cased miniatures of every Chevrolet car ever made....OK--understood haha.