I've always wanted a Fiero, last September I bought an 87 GT, 5 speed, with only 46k. Sat for years at a time, and came with all the typical old car/low miles problems. In the first 60 days I replaced all the brake lines, and hoses. New calipers in back, as the fronts were upgraded with the Fiero store's vented brakes from a Grand Am by the previous owner. Complete tune up with new distributor, cap and rotor, plugs, wires, coil, and after market ICM that came with new dizzy switched out with a Delco. All ignition components are Delco....she reeeeally didn't like the non-Delco coil and plugs I tried first. Also replaced the water pump and driver's side coolant tube, as well as the MAP sensor when the idle got a little jumpy.
Car ran like a tank even before I replaced anything...drove it home on a 4 hour drive the night I bought it. My first car was a Sunbird GT, so I have a strong love for the 60 degree V6.
Last week it started hesitating and bucking slightly at low rpm's, and generally only when the car is already warm. It also has begun giving me very long starts when the car is already warm. The serp belts squeals and screams ONLY when I get the long start...In the morning when she's cold, it fires on one crank, and zero belt noise. The serp belt is also new.
The long starts only when warm combined with a hesitation tells me the injectors are leaky, but the belt noise only with the long starts makes me think it could be timing? The engine is properly timed, and the plugs properly gapped. The new plugs look good when pulled out for inspection, dizzy rotor is good. I know these motors came with weak timing chains, could that be doing this? Hesitation completely stops the higher you rev the motor, and going 70 in 3rd gear with the engine screaming causes no problems, at all. So I'm thinking it's not the fuel pump.
All in all, I've had great luck so far, and the car does run very well. Oh, and I've gotten zero check engine codes.
Pull tach filter then try. You will lose tach but iffy filter will cause problem running the engine. See my Cave, HE Ignition
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
First of all welcome to the forum and the world of Fieros! There is a wealth of information here and a good search function. Hard start when hot is sometimes ignition module and although you said you replaced it they are not always good. If you were inclined to replace the injectors, it's a pretty easy task and you can get them cheap at Rock Auto. I have a similar problem with mine but I think I'm going to try a custom chip next as it's a turbo. Regardless I'll be watching this post so please be sure and post the fix when you find it so folks searching in the future will be helped as well!
Still getting the low end hesitation. Only happens when the engine is already warm, and when I'm either deaccelerating, or holding throttle steady for more than 10 seconds. Acceleration and steady throttle at 3k or above is fine.
so I watched the videos, it is doing something similar to what mine was as well. Did you get it fixed yet? If not , I solved my similar problem by disconnecting the MSD module and Accel coil and reinstalling a stock one, problem gone! Since you don't have this, it may still be ignition related, if anyone on here is near you perhaps they have another ignition control module you could try in case you got a bad one. Did you keep your old parts? You said it ran like a tank before this (I assume that's a good thing.)
It's the 3rd ICM I've used. When the 1st and 2nd one were bad, the car was basically losing spark above 3000rpm, and the tach was all over the place. Also the MSD coil was replaced with a delco coil. Literally the entire ignition system is ac delco. It's not acting anywhere near as poorly as when the ICM was bad. I've pulled the tach filter, no change.
It feels like the timing is off or it's something in the dizzy itself. I'm starting to think it's maybe the actual distributor? As I replaced the whole thing when I did the tune up, as the prongs were all rusty...I figured why not just do a new one. However, the problem ONLY happens when it's warm..that makes me think the sensors are off. It's literally 100% perfect at all speeds when it's cold. Frustrating...she runs so well.
What's your idle speed? Anything over 1000 rpm is a vacuum leak. I would suspect arcing on the ignition wires and/or a bad ground. Your fuel gauge should not be wandering around as much as it does.
From what you describe it's most prominent or present when the motor is warm or in other words in closedloop operation. From the sound of the first video and given what you have already replaced, I would double check and make sure the plug wires are seated properly as they are often difficult to remove from the plugs which increases the chances of damaging one in a way you can't readily see that can result in an intermittent misfire, I just went through that with a set of wires. If that doesn't stop the problem the TPS sensor would be high on the list, I got water in one on an 85 TPI motor while cleaning the throttlebody and it made the motor buck and kick with throttle input. There are instructions floating around on how to test it with a multimeter, you want to check for a smooth variable resistance or voltage change through its range. It wouldn't be a bad idea to check the fuel pressure, I had a bad pump unknowingly take me on a 500 mile round trip towing a car on the way back before it finally deteriorated enough for me to suspect it. Prior to that it caused an intermittent stumble on throttle input.
Replaced TPS, no change. Unplugged the oxygen sensor and drove around to force a code 13 and open loop operation. No change. Plugged the o2 sensor back in, cleared the code, and now the idle is all over the place for about 20 seconds until it settles. Idle was fine between changing the tps and unplugging the o2. Idle was fine before this, 900rpms when warm. And still have the hesitation...getting frustrated.
Originally posted by pbisaillon83: Replaced TPS, no change. Unplugged the oxygen sensor and drove around to force a code 13 and open loop operation. No change. Plugged the o2 sensor back in, cleared the code, and now the idle is all over the place for about 20 seconds until it settles. Idle was fine between changing the tps and unplugging the o2. Idle was fine before this, 900rpms when warm. And still have the hesitation...getting frustrated.
If you have the old distributor and it's still functional, put it back in and test it. You were suspecting the new one as a possible cause. The distributor or one of its elements can be heat sensitive when it's malfunctioning. When my OE distributor gave me problems, the symptoms were 3 stalls requiring about 5 minutes each of cooling off to travel 14 miles home. When I took it out and attempted to clean up the rust you described, it stopped working altogether. I have had a tach filter arc to ground before and that is instant hot or cold.
If that doesn't fix it, the problem maybe mechanical.
[This message has been edited by Joseph Upson (edited 05-07-2016).]
Mechanic just called. Hes saying the map and EGR sensors are throwing the communication between the sensors off, and that both need to be replaced with ac Delco parts. I'm finding this hard to believe, but the problem does only occur when the car is warm and running in closed loop. Thoughts? Comments? Thanks!
Originally posted by pbisaillon83: Mechanic just called. Hes saying the map and EGR sensors are throwing the communication between the sensors off, and that both need to be replaced with ac Delco parts. I'm finding this hard to believe, but the problem does only occur when the car is warm and running in closed loop. Thoughts? Comments? Thanks!
Interesting although I know from experience on an 86 TPI MAF sensor Camaro that a MAF sensor malfunction can set an EGR code 32 although there is no problem with the EGR. If I recall correctly the EGR is not active at part throttle. I'd check the pipe to the intake plenum and make sure there is no intermittent leak as a result of thermal expansion exposing a crack, then unplug the vacuum signal/line to the EGR, plug it and then test drive it. A code 32 may or may not set but if it is the culprit the misfire should disappear because there will be no exhaust gas allowed into the intake to disrupt the air/fuel mix.
The EGR itself is vacuum activated so if it is sound which can easily be checked with a hand held vacuum pump and sealed properly at both ends, I see no benefit in replacing it. The control valve for it on the other hand is a different story and again if the EGR valve is disabled by unplugging it you should still eliminate the misfire if the EGR system is the cause.
[This message has been edited by Joseph Upson (edited 05-11-2016).]
Only happens when the engine is already warm, and when I'm either deaccelerating, or holding throttle steady for more than 10 seconds. Acceleration and steady throttle at 3k or above is fine.
