Engine is surging from 600 rpms-2500 rpms after i start the car. it does this til it finally cuts off. it comes and goes sometimes it will do it and other times its fine, but it seems like it only does it when its hot. if i start the car for the first time in a few days, it will start and run fine, but once it heats up it wants to surge. the car has no EGR, no smog pump, and i put a new IAC valve on it. please help.
Engine Surging!!!!! Please Help!!!!!
- Thread starter Chris Walker
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have you pulled codes?
i have not heard of it with stangs, but on a Porsche i had many moons ago, i fixed a surge with a new lambda sensor. for some reason, when it went into closed loop, that sensor was making the idle wander/surge.
good luck.
i have not heard of it with stangs, but on a Porsche i had many moons ago, i fixed a surge with a new lambda sensor. for some reason, when it went into closed loop, that sensor was making the idle wander/surge.
good luck.
88stangmangt
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get the car warmed up to operating temp. Then unplug the Idel air control. If the car dies you need to turn the idel screw in to bump idel up. When you unplug the IAC the rpm should drop but it shouldnt die if it surges while the iac is unplugged try bumping the idel up some and see if it stops then plug the iac back in. I did this last nite to my buddys 347 stroker and it quit surging and ideled perfect. After you adjust idel set the tps to
.95-.98 and reset the eec by disconecting the neg batt cable for 15 mins or so.
.95-.98 and reset the eec by disconecting the neg batt cable for 15 mins or so.
88stangmangt
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dvs bullet
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Another vote on checking the tps sensor, I had the same prob. the sensor went faulty. When I checked the voltage it was way out of wack, and it wouldn't go up past .70 volts. Good luck 
there is another school of thought on the idle situation, hence why (i think) some cars dont adapt to the above attempts. it comes from Stang and Two Birds (et al), and i respect his opinion.
the computer supposedly zeroes out everything upon start up, each time. so even if you set everything with regard to the idle, manually, the puter will do whatever it can to get your idle back down to ~650 RPM.
this normally comes up when folks are trying to raise their idle (and perhaps disconnecting the IAC) to cure idle surge. but it kinda fits in here (just something to be aware of while trying things).
good luck.
the computer supposedly zeroes out everything upon start up, each time. so even if you set everything with regard to the idle, manually, the puter will do whatever it can to get your idle back down to ~650 RPM.
this normally comes up when folks are trying to raise their idle (and perhaps disconnecting the IAC) to cure idle surge. but it kinda fits in here (just something to be aware of while trying things).
good luck.
if you are talkin about the TPS, you probe the ground and return wires on it (the third wire is 5 volts). many folks cut back a smidge of the insulation and probe them (with the wires all connected).
when you check it, for fun, open the throttle and watch for a nice clean even sweep from your starting voltage (~1.0 volts or less) to WOT (~4.5 volts). if there are breaks or dips in the reading, get a new one. also, an analog VOM works best for seeing the trend (needle sweep).
if your initial reading (at rest) is high (like over 1.50 volts) and you want to adjust it, try to loosen the screws and adjust it till it is in range. if you cant adjust it, many folks drill out the holes, so that the enlarged bosses allow adjustment.
for checking the IAC, one needs a dwell meter. it is a pain and not worth doin, IMHO).
good luck.
when you check it, for fun, open the throttle and watch for a nice clean even sweep from your starting voltage (~1.0 volts or less) to WOT (~4.5 volts). if there are breaks or dips in the reading, get a new one. also, an analog VOM works best for seeing the trend (needle sweep).
if your initial reading (at rest) is high (like over 1.50 volts) and you want to adjust it, try to loosen the screws and adjust it till it is in range. if you cant adjust it, many folks drill out the holes, so that the enlarged bosses allow adjustment.
for checking the IAC, one needs a dwell meter. it is a pain and not worth doin, IMHO).
good luck.
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