Hey guys, I have a wierd problem. I have a stock 2.8 auto. its an 87 if that maters. My car stumbles sometimes. Its feels like it just misses random ignition strokes sometimes(almost like a missfire, but much more noticable). The warmer the car is, the less I notice it. It started after the car overheated one day due to it being low on coolent from a bad leaking heater core. I fixed the heater core and have recently put in new spark plugs, ICM, and air control sensor. I can drive the car just fine, just the random missing stroke is hell of annoying. anyone got any ideas on how to track down this issue.

I would look for loose ground connections on the engine block. Overheating can loosen a bolt or two.

Check your fuel pressure.

Didn't replace the spark plug wires? Replace the spark plug wires, the distributor cap/rotor, and the ignition coil.

Hello where are all the grounds? When i start the car from a really cold start, the volt-meter for the batery is really low till i press on the gas. Then it jumps up to where it normally should be.

I replaced the plug wires and the fuel pump ago. Could be the coil pack or the pickup coil.

quote Originally posted by fieromatty: Hello where are all the grounds?

ANY wire bolted to the engine block or sheet metal is a ground. There is the battery cable....there are a couple buried down below the throttle body, there is one at the transmission. There are others.

quote When i start the car from a really cold start, the volt-meter for the battery is really low till i press on the gas. Then it jumps up to where it normally should be.

The regulator is switching from the battery to the alternator when you press on the accelerator. Maybe your battery is weak.

quote I replaced the plug wires and the fuel pump ago. Could be the coil pack or the pickup coil.

Your car has an ignition coil...and a pickup coil. Either one could be bad; here is a test for each....(pickup coils tend to be bad if they look bad)

[This message has been edited by Gall757 (edited 11-19-2014).]

So, here is an update.

I put a brand new distributor, coil-pack, spark plugs and wires in the fiero. The car feels better; however, I still have this weird stumble sometimes. Its more noticeable at high speeds then anything else.

Its like it dies for .5 sec or something and its not consistent. I am going to replace the battery cables here shortly. Can you guys think of anything else that might be causing this.

-fieromatty

Did you check the fuel pressure?

a new fuel pump and fuel filter where put in about 3 months ago.

Had the same problem on mine turned out to be plug wires. Make sure they are not touching each other. I made the mistake of zip tying them together to keep them away from heat. After I corrected it ran fine.

lol ill give that a try.

I had a similar problem on my 87 2.8 along time ago. It started after I did a big ignition freshen up like you did including a new distributor. I spent a lot of time troubleshooting, including all the things listed above and finally gave up. When the opportunity popped up later, I let Ed Parks talk me into swapping in a 3.4 pushrod. A short time later, I noticed that the distributor on the 3.4 was not in good shape and replaced it with the one from my old 2.8.

Boom, the 3.4 now had the same stumble. Check your distributor. I never thought of that when it was on the 2.8 because it was a new part.

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[This message has been edited by 1MohrFiero (edited 12-11-2014).]