Foxbody issue for 2 years

Thepreacher413

New Member
Oct 3, 2022
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0
1
I’ve been having this issue for 2 years. Hasn’t been drove because I can’t fix it. When I crank it up cold it’s fine, then when it drops to idle rmps it will dip to 200 rpm real fast and then back to 700 back and forth fast until it dies. When I rev it up, it will come back down to 1000 rpms and hang there for 2 seconds and then come back down to 700 before it starts surging again. And it’s pretty rough feeling. I have done everything foxbody guys have told me to do. I’ve cleaned the egr, the maf, the iac. There’s no vacuum leaks. I have replaced icm, spark plugs, wires, rotor, rotor cap, ignition coil, thermostat, cleaned throttle body and put new gasket on it. I cleaned the maf and iac but they could still be bad idk. Can someone please help. Btw by temp gauge doesn’t work at all. I think it’s a temp sending unit but it might play apart in a electrical problem if y’all think it’s that which I hope it’s not because that will be a nightmare. Oh yeah the tps is set to 0.98 with a base idle reset. Thanks
 

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
39,455
15,302
224
WHat year is the car?

What does it do if you unplug the IAC? Does the idle still surge? What sort of modifications are done on the motor?

How have you verified there are no vac leaks? Did you use a smoke machine?
 

Boostedpimp

15 Year Member
May 8, 2003
1,433
565
154
Sounds weird but I just went through this with one of my cars. I went over everything multiple times for months until I got the idea to spend the ten minutes to pull the the ECU and take a peak at it.. I always assumed it was fine since I was getting the code 11 which is the system check. I've had failed ecu's in the past which either would cause the fuel pump to run continually or not at all. Against my better judgement I pulled it and it ended up having a failing power supply, voltage regulator and leaking capacitors.
 

Thepreacher413

New Member
Oct 3, 2022
7
0
1
Sounds weird but I just went through this with one of my cars. I went over everything multiple times for months until I got the idea to spend the ten minutes to pull the the ECU and take a peak at it.. I always assumed it was fine since I was getting the code 11 which is the system check. I've had failed ecu's in the past which either would cause the fuel pump to run continually or not at all. Against my better judgement I pulled it and it ended up having a failing power supply, voltage regulator and leaking capacitors.
I really hope that’s not the problem but I will have to look. Ecu’s are crazy exspensive nowadays and I have no clue on how to soder a capacitor
 

CAMTWO1070

Active Member
Dec 17, 2021
141
43
38
Sounds like your problem could be that you need a new halls effect sensor inside the distributor or could be wiring related or the coolant temp sensor or the IAT sensor isnt grounding or is going bad,,Here are the specs for them to do tests by...

20*C-3.1V, 40*C-2.2V, 100*C-0.5V

Here are the specs for the Intake Air Temp sensor..

0*C 3.9V, 20*C 3,1V, 40*C 2.2V

What I like to do is pull up my Moates dashboard then see what the sensors say against a calibrated thermometer and point n aim temp gun plus my good old portable weather station I take to the track....

For your temp oe IAT sensor issue its easy to change the sensor just make sure the thing is grounded good....

I'd try removing the 02 sensors and cleaning them in lemon juice and then cleaning the lemon juice off with rubbing alcohol...

Do you have the TAB TAD,Thermactor and EGR still hooked up?

Have you tried to pull up error codes and is the CEL on?

Have you tried checking to make sure you have the right TFI module and that your distributor is in good working order and grounded good plus set at 10* BTDC? ......

Id do a voltage check to make sure everything thats supposed to be 12v like MAF,Injectors,EEC relay fuelpump relay and IAC matches the battery voltage.......? If not your salt n pepper shakers may need to be cleaned up...

Have you checked the ground wires to make sure none are busted?

Have you done a fuel pressure check?

Have you tried testing the injectors with the cheap fuel injector tester on amazon?
 
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CAMTWO1070

Active Member
Dec 17, 2021
141
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$129...not bad and they get it right.
Yep....I had 3 computers repaired by them . All worked as intended afterwards and not so as intended before......LOL

When I did business with them they were in Florida...Now theyre based out of Georgia as I have to send another one on on Monday morning for repair.....
 

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Mindseye007

Active Member
Oct 21, 2020
162
18
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Sounds weird but I just went through this with one of my cars. I went over everything multiple times for months until I got the idea to spend the ten minutes to pull the the ECU and take a peak at it.. I always assumed it was fine since I was getting the code 11 which is the system check. I've had failed ecu's in the past which either would cause the fuel pump to run continually or not at all. Against my better judgement I pulled it and it ended up having a failing power supply, voltage regulator and leaking capacitors.

what does the failing power supply, voltage regulator Look like?
 

KRUISR

5 Year Member
Apr 16, 2015
1,364
608
133
And the iac idles higher when unplugged like it is suppose to
Actually its the reverse. Idle should drop when IAC unplugged.

What procedure are you using for Base Idle Reset (I have seen a few different versions)? This is the one I have had success with:

Go to post #9 for the steps.