I have a 86 Fiero with the 2.5L Duke and the Isuzu 5 speed tranny.

Lately the car misses/stumbles/runs rough when the engine is cold. It is most noticeable when I am above 1900 RPM in any gear. Basicallly from when I start the car until it gets to around 180 degrees on the temp, it will start missing/stumbling, etc, when the RPMs climb above 1900 RPM. Not bad enough I can't drive it yet (its my DD) but its getting to be annoying. It also seems to be affected by the load on the engine--ie when if I have it in Neutral and rev it, it doesn't miss, accerate in second gear above 1900 RPM, it starts to miss.

I can start shotgunning parts into it--plugs, wires, etc, but wondered if anyone had a more structured troubleshooting approach I should try.

Thanks

Isaac

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86 Fiero 2.5L, 5spd.
00 Ford Focus 2.0L 5spd
66 Chevrolet C10 250 cid, Powerglide

I would say it has something to do with your ignition system. When was the last tune up on the car? It is quite possible that a plugwire is begining to fail . It could be your cap or rotor as well. Plugs wires and a cap and rotor shouldn't hurt the wallet to much. Check your wires for burnt marks or chaff marks maybe one might have got rubbed the wrong way who knows.

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HARDCORE SBC CRONIE AND PROUD OF IT ! GOT TQ ?

My duke had little torque until the temps got hot. Then I cut the cat off.

It still doesnt have much grunt when its cold, but I dont stall anymore when its cold out. Its a freshly rebuild engine, so I am pretty sure the cold performance just wont be good anyway. Remember, the computer fuel injection is only slightly better than a carburated fuel intake, and they dont have much cold temperature performance either.

i can only suggest a full tune up with all the parts just don't forget the pcv and fuel filter... unfortunantly the fuel filter can be a pain in the arss cause its a threaded filter...i just saw one today that I worked on that ONLY had rust on the threads and no where else on the lines!!! my boss and I both thought it was odd that the only place to rust was the place that needed the work...lol anyways try a tune up and see what ya get....if not then get a single wire and swap it out and see what you get....inspect your cap and rotor to see what kind of wear you have in there....pull the plugs and see what kind of shape that thier in.....unplug the o2 sensor and see if the engine still runs the same or if there is a change.... check the simple things first to rule out what works from what doesn't..


Brian

quote Originally posted by WrenchingPilot: I can start shotgunning parts into it--plugs, wires, etc, but wondered if anyone had a more structured troubleshooting approach I should try. Thanks Isaac

http://winaldl.joby.se/
www.aldlcable.com

Stick a plug in the vac line going to the EGR valve and take a drive.

Things to check --not buy , the tps will cause this off launch. iac & passage, mat & cts , plugs & wires, fuel pressure & filter, egr like Phil mentioned. All vacum lines...

quote Originally posted by 3800superfast: Things to check --not buy , the tps will cause this off launch. iac & passage, mat & cts ,... All vacum lines...

Mine still does this and I have been up to date and very conciensious on tune ups. It just hasn't bugged me enough to check out the above mentioned parts since the car gets up to temp pretty quickly. Plugs, wires, cap, and rotor will help, but I think the main problem is somewhere in the iac & emmissions systems. I think here aldl would help a lot if you have it.

Thanks for all the replies people.

Tonight I replaced the plugs, wires, distributor cap, and rotor. When I pulled off one of the plug wires, it broke just above the boot over the plug. The conductor in the lead was very stiff and work hardened. Hopefully that was the cause of my problems. If not, you've given me plenty of suggestions on where to go from here.

Thanks again guys!

Isaac

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86 Fiero 2.5L, 5spd.
00 Ford Focus 2.0L 5spd
66 Chevrolet C10 250 cid, Powerglide