stumbles for some reason? (Page 1/4)
katie80 AUG 27, 12:58 PM
i have an 84 2.5l fiero that has been nothing but problems the whole time i’ve had it. i just had it all sorted for about 2 weeks. yesterday i was driving across town on the highway and the car started to die for maybe a quarter to half second and come back. the check engine light would come on when this happened. i eventually figured out if i just lower the revs by disengaging the clutch or putting it in neutral it would stop doing that for a little bit. it’s not a fuel system issue (i think) as i replaced every part in it at this point (fuel pump, filter, regulator, injector) it only does it after a little while of cruising at higher rpms. it doesn’t do anything weird if i accelerate hard. only when i’m cruising at around 2-3k rpm. ignition maybe?
Patrick AUG 27, 02:40 PM

Possibly the TPS has developed a dead spot. Check the TPS for continuous readings from idle to wide open.
Dennis LaGrua AUG 28, 01:13 PM
When was the last time that you changed the fuel filter?

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katie80 AUG 28, 02:07 PM

quote
Originally posted by Patrick:


Possibly the TPS has developed a dead spot. Check the TPS for continuous readings from idle to wide open.


ok which pins?
katie80 AUG 28, 02:08 PM

quote
Originally posted by Dennis LaGrua:

When was the last time that you changed the fuel filter?



2 weeks ago. maybe driven a hundred miles. brand new fuel pump, strainer and gas tank was cleaned right after that too.
katie80 AUG 28, 02:39 PM

quote
Originally posted by Patrick:


Possibly the TPS has developed a dead spot. Check the TPS for continuous readings from idle to wide open.



I got 6.7 ohms with the butterfly valve closed to 3.92 ohms at WOT. I have a second throttle body with the sensor on it (same year, different sensor for some reason. that one reads around 3.9 ohms with the valve closed, 6.7 ohms at WOT. reversed for some reason? it's from another 84. measured across the b and c terminals.
Spoon AUG 28, 03:28 PM

quote
Originally posted by katie80:

i have an 84 2.5l fiero that has been nothing but problems the whole time i’ve had it. i just had it all sorted for about 2 weeks. yesterday i was driving across town on the highway and the car started to die for maybe a quarter to half second and come back. the check engine light would come on when this happened. i eventually figured out if i just lower the revs by disengaging the clutch or putting it in neutral it would stop doing that for a little bit. it’s not a fuel system issue (i think) as i replaced every part in it at this point (fuel pump, filter, regulator, injector) it only does it after a little while of cruising at higher rpms. it doesn’t do anything weird if i accelerate hard. only when I’m cruising at around 2-3k rpm. ignition maybe?



Cruising may not have anything to do with it. How is your tach needle responding when the engine begins to die? Does it quiver a little or does it take a deep dive and then recover quickly? Either one may point to ignition. Try holding the rpm at 2500 rpm in neutral for a minute and see if engine starts to die and monitor the tach. If it does dies or stumbles watch the tach needle to see how its reacting. A quick drop of the needle could mean an intermittent break in the ignition circuit.

If so, then find a willing subject and have him/her hold a 2500 rpm and you can start wiggling the engine wire harness & connectors to see if that causes the problem. In addition pull the center console to gain access to the ECM and wiggle those wires (each one of them) as well with engine running. I had same problem with my 2.8 and it was a loose wire in one of the ECM connectors that fed the ignition module.
I could make the engine rpm take a dive by merely pushing the wire side to side at the ECM connector.

I deliberately didn't mention to check all the ground wires. I'm sure ORGE will be along shortly to mention those important details.

Spoon

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Patrick AUG 28, 03:46 PM

quote
Originally posted by katie80:

I got... ohms



If you're going to be checking for resistance, then as stated earlier, just make sure there are no "dead" spots. I have no idea why the resistance readings are reversed on your two different Throttle Position Sensors, except for one possibly being incorrect for a Fiero.

When I check a TPS, it's by using WinALDL and reading the voltage values.
katie80 AUG 29, 12:31 AM

quote
Originally posted by Patrick:

If you're going to be checking for resistance, then as stated earlier, just make sure there are no "dead" spots. I have no idea why the resistance readings are reversed on your two different Throttle Position Sensors, except for one possibly being incorrect for a Fiero.

When I check a TPS, it's by using WinALDL and reading the voltage values.



sorry, I meant to include in that. the sweep seems fine. I used an analog multimeter and the needle doesn't do anything funny from closed to wot. didn't see any dead spots.
katie80 AUG 29, 12:34 AM

quote
Originally posted by Spoon:


Cruising may not have anything to do with it. How is your tach needle responding when the engine begins to die? Does it quiver a little or does it take a deep dive and then recover quickly? Either one may point to ignition. Try holding the rpm at 2500 rpm in neutral for a minute and see if engine starts to die and monitor the tach. If it does dies or stumbles watch the tach needle to see how its reacting. A quick drop of the needle could mean an intermittent break in the ignition circuit.

If so, then find a willing subject and have him/her hold a 2500 rpm and you can start wiggling the engine wire harness & connectors to see if that causes the problem. In addition pull the center console to gain access to the ECM and wiggle those wires (each one of them) as well with engine running. I had same problem with my 2.8 and it was a loose wire in one of the ECM connectors that fed the ignition module.
I could make the engine rpm take a dive by merely pushing the wire side to side at the ECM connector.

I deliberately didn't mention to check all the ground wires. I'm sure ORGE will be along shortly to mention those important details.

Spoon





it's been a couple days since I drove it but I do believe the tach was jumping around, at the same time as the engine freaking out and the engine light. i have a feeling it is ignition related and not a bad ground since the problem IMMEDIATELY stops when I let the rpms drop. I will try doing that in neutral to see if I can replicate the issue. I think I'd have to drive it for a bit before that so the engine is nice and toasty since I had been driving at temp for around 10 mins before the issue began.