My 1987 SE 4-cyl had a backfire/stumbling problem whenever I stomped on the accelerator. In trying to fix the problem I replaced the MAT, MAP, spark plugs, spark plug wires, the IAC valve and the coil packs. The car ran much stronger, BUT it still hesitated when I stomped on the gas... I also got underneath my car and replaced the fuel filter, to no avail... After these "hit-n-misses" I decided that it was time to take the car to a trusted mechnic with diagnostic equipment.
He tested my computer, it showed no codes, however, my 02 sensor was acting up. He replaced it.
Also, he noted that I had cheap spark plug wires, and that I should replace them (note to self - never skimp when buying replacement parts)... Also the "new" coil packs in my car were not AC-Delco... So he recommended I replace them (note to self - do not skimp), and then he also recommended changing the back plate to which the coil packs are attached... The old backplate was corroded....
Result: Car runs brand new again, no more hesitating/backfiring when I stomp on the accelerator!!!
I know that there were a few others out there having the same problem I had with their 87-88 2.5.... Hope this helps... Use AC-Delco parts!!!
My
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88 GT, 5-spd
87 SE 4-cyl, 5-spd
