G.T. Fieros

I have an 86' GT which I've wanted since I was 9. (only took 21 years ). I've managed to get it almost how i want it. Still working on it. anyway I seem to have some sort of issue when i'm cruising between
1000 -2500 rpm. 1st, 2nd, 3rd, 4th gear doesn't matter. The car chugs & bucks. If there is a load on it she takes off like a rocket and there is no issues if my foot is completely off the accelerator. could someone please help me out? I've changed the pick up coil and the EGR valve. I do have an exhaust leak at the manifold.

I had nearly the same experience from the end of last fall to the start of this season - bucking only on cruise/stead lower rpms, but the car seemed to perform fine under hard acceleration or higher rpm highway driving. One thing led to another to get it finally sorted out.

First almost by chance I found that my throttle body stop screw wasn't set propery. I reset that and found the car didn't really want to run properly. Reset the IAC motor after that and it was a little better but still not right. This was after a full tune up was done (cap/rotor/plugs/wires/coil).

After that I checked the timing and found that it was set way out - too far advanced. Backed it off and again the car was running better, but still a hesitation.

The final part was the O2 sensor. The car smelled rich - turns out the O2 had completely failed and only threw a lean code. It had failed with a permenant lean reading and the computer was trying to over compensate.

For me that was the final piece of the puzzle. With the O2 sensor, the complete tune up and the adjustments above that got rid of the bucking.

I would start with a basic tune-up and go from there. It could be as simple as done plugs or a bad spark plug wire. Does the check engine light come on at all or has it come on in the past?

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Ryan - 86 GT

Like Ryan said, start with a tune up. Do you know when the car had it's last proper tune up? Plugs need to be gapped properly, use stock A/C Delco's, stay away from Bosch platinum and any fancy plugs. I've use regular NGK's plugs & wires in cases where I couldn't get Delco's, I won't touch Champion parts. Make sure wires are bundled up properly and run correctly. Cap & rotor can make a big difference, they can crack and you won't see it but water finds it. Check inside it for corrosion. I've seen sensors go and not through a code, they will still preform but on the edge of their limits and throw the computer out of whack. The O2 is a good place to start but can be a pain in the ass to remove without the proper tool.

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87 GT 3400 Green
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