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help with surging idle

FatBoyGrimm

FatBoyGrimm

New Member
I recently purchased my first fox body, it has some modifications, AFR heads, BBk throttle body, Trickflow Intake, and a mild street cam(not sure which kind or what degree lobe). I am having a problem With the car surging at idle. I have cleaned the MAF sensor which helped a little and after retraining the idle it still surges for about 45 sec. then balances out around 800 rpms.I can even turn the A/C on, but the second i have to stop with the rpm's at 1500 or higher the car shuts off. and it only does it when the A/C is on. otherwise it drives fine. I am trying to fix this issue with out deleting the A/C. has anyone had this issue. and does anyone know a way to fix it
 
Blown347

Blown347

Moderator
Staff member
Check TPS voltage and clean the IAC. Those are usually idle problems. The TPS with key on engine off should be less than 1 volt. And the IAC gets gummed up from time to time.

So far as the AC I think that is a separate issue. I'll see what I can find on it.
 
FatBoyGrimm

FatBoyGrimm

New Member
thanks for the info. after testing the TPS sensor it measured good. Right around .8 volts. and the IAC i just replaced. but i have heard that aftermarket IAC's Don't always work right. But not sure if that is true.
 
John2002

John2002

Guest
I went down that same list as you, do you know where the PVC valve is??? After I changed that it ran way way better. Also, I don't know if you still have O2's on your exhaust but they also needed to be replaced on my car.
One more thing that made a difference was that "spout connector" (don't ask..LOL) its that small gray tab on the other end of the wire loom that plugs into the bottom of the distributor. I don't know why but it seems to oxidize a bit. Oh...one more thing I had to find out the hard way...a worn out TFI!!! When they get hot they make a big differece on engines performance when the engine gets hot. Its a hard to get off if you don't have a thin wall 5 mm socket..... These things all seem to give the OBD week or delayed signals when they start to wear out...My buddy had to borrow and old scanner to help me with ghosts in my OBD...Good Luck...
 
FoxBodyMustangs

FoxBodyMustangs

Administrator
Staff member
FatBoyGrimm said:
I recently purchased my first fox body, it has some modifications, AFR heads, BBk throttle body, Trickflow Intake, and a mild street cam(not sure which kind or what degree lobe). I am having a problem With the car surging at idle. I have cleaned the MAF sensor which helped a little and after retraining the idle it still surges for about 45 sec. then balances out around 800 rpms.I can even turn the A/C on, but the second i have to stop with the rpm's at 1500 or higher the car shuts off. and it only does it when the A/C is on. otherwise it drives fine. I am trying to fix this issue with out deleting the A/C. has anyone had this issue. and does anyone know a way to fix it
Click to expand...

Check all your vacuum hoses one may have popped off somewhere or an old hose...
 
FatBoyGrimm

FatBoyGrimm

New Member
yeah. I checked the PCV valve when i cleaned the MAF sensor, and I have EGR delete so no cat's or 02's. I did a smoke test on the vacuum system and no leaks popped up. as far as the TFI it looks to have been replaced when the MSD Distributor was installed. is there a way to test the TFI before removing it or replacing it?
 
Blown347

Blown347

Moderator
Staff member
FatBoyGrimm said:
yeah. I checked the PCV valve when i cleaned the MAF sensor, and I have EGR delete so no cat's or 02's. I did a smoke test on the vacuum system and no leaks popped up. as far as the TFI it looks to have been replaced when the MSD Distributor was installed. is there a way to test the TFI before removing it or replacing it?
Click to expand...

The TFI would make it to where your car would shut off randomly, and not start for a while when it got hot. TFIs fail from heat. So I don't think that's the problem.

Do you have that little plug for the end of the EGR harness? That can cause problems as well if the EGR is deleted. It fools the computer into thinking its receiving an EGR signal.
 
Blown347

Blown347

Moderator
Staff member
Buy the plug above. You can keep the EGR delete this will just fix the problems associated with deleting it.
 
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