Car issues again (Page 1/9)
Monkeybean007 MAR 23, 12:02 AM
85 gt v6 2.8l -- My car runs amazing when I first start it up and start driving but when the car warms up it starts to random misfire, and I get low acceleration and power under load . I've replaced some stuff so far

-o2 sensor
-tps
-alternator
-new spark plugs
-new spark plug wires
- fuel filter
-fuel pump

I think thats everything I can think of off the top of my head, I also took apart egr and cleaned it out and gave it a good scrubbing. Any help would be appreciated I love this car and just want her to run well.

Gonna try cleaning and testing IAC tomorrow as that seems to be a common issue from all of the readings I've done on the forums here.

[This message has been edited by Monkeybean007 (edited 03-23-2020).]

TM_Fiero MAR 23, 06:55 AM
Maybe the ICM. They routinely go bad in Fieros. Members more knowledgeable about this will chime in. Any check engine lights?
wftb MAR 23, 08:49 AM
The ceramic material inside the cat convertor tends to crumble with age and sometimes will almost completely block the exhaust flow. It is pretty random, sometimes the chunks will settle out and you dont notice it as much. Usually a good full throttle rip through first and second gears will have the engine choaked pretty well.

The ICM sometimes gets corroded and needs to be cleaned and a new layer of heat transfer paste put on. That would be consistent with it running rough after it warms up.

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86 GT built 2.2 ecotec turbo
rear SLA suspension
QA1 coilovers on tube arms

[This message has been edited by wftb (edited 03-23-2020).]

Gall757 MAR 23, 11:06 AM
Another Idea:

Engines running cold use default computer values, while a hot engine uses sensor inputs. IF one of the sensors is bad, it will only bother the engine when it is hot. The coolant temperature sensor, (CTS), is a candidate. ICMs will do this also because they expand when they get hot, and sometimes break solder joints on the internal board.

[This message has been edited by Gall757 (edited 03-23-2020).]

Monkeybean007 MAR 23, 11:17 AM
I've already replaced coolant sensor and no codes are being thrown unfortunately, replacing/removing cat is also on my list of things to do, I was thinking sensors as well, so icm seems to be the next thing I should check out?
MarkS MAR 23, 02:55 PM
Any back-firing when its warm & stumbling?

theogre MAR 23, 04:35 PM
What new plugs and plug wires?
New either could still have problems and more so w/ "gimmick" or "Performance" ignition parts

discon the tach filter and See my Cave, HE Ignition

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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)


The Ogre's Fiero Cave

Monkeybean007 MAR 23, 05:05 PM
It stumbles and dosent like to accelerate past half Throttle
Monkeybean007 MAR 23, 07:08 PM
Just replaced IAC valve as the other one was stuck out , didn't fix the issue , slowly loosing my mind.
Patrick MAR 23, 07:46 PM

quote
Originally posted by Monkeybean007:

85 gt v6 2.8l -- My car runs amazing when I first start it up and start driving but when the car warms up it starts to random misfire, and I get low acceleration and power under load.



Not sure why you'd think the Idle Air Control valve would have any effect on a random misfire and beyond half-throttle issue.

I agree with what Gall posted. Get a scanner (or WinALDL) on there to see what's going on with the sensors.


quote
Originally posted by Gall757:

Engines running cold use default computer values, while a hot engine uses sensor inputs. IF one of the sensors is bad, it will only bother the engine when it is hot.