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Engine stumbles - EFI Question

2285 Views 9 Replies 3 Participants Last post by  zwede
Sorry not sure this is the right area to post this question. I know this is not exactly a Chevelle question, but I'm sure someone here can answer my question.

My daily driver for going to work is a 95 Cutlass Cerria that I inherited from my mother. The engine is a four cylinder 2.2L. It has a severe stumble/hesitation at highway speed. This happens during crusing, light/medium accelleration and light deaccelleration. The engine just runs horrible with a jerking/stumble or hesitation. At WOT it runs fine, I don't feel any stumble, good power at least for a four banger. Idle is smooth.

The check engine light is NOT on and when scanned there are not any codes. I've had a Chevy dealer and a local repair shop look at this. Both acknowledge the problem and both are completely clueless. Without any codes showing they just say "can't do anything without knowing a trouble code". Whatever happened to doing real trouble shooting without a computer?

I've replaced a few of the simple and cheap things, spark plugs, spark plug wires and fuel filter. Didn't help anything.

I don't want just to throw expensive parts at it hoping something works. The cheapest injectors I've found run about $70 each. My EFI knowledge is severly limited as is test equipment other than a simple volt/ohm meter.

So where do I start trouble shooting this? This car only has 86k miles on it, so there is still a lot of life left in it. I just can't stand a horrible running car.

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two things to look at as I have fixed hundreds of those things. Get an analog voltmeter and do a voltage sweep with key on, engine off on your TPS (throttle position sensor). Looking for a clean sweep from around .5 volts to just over 4.5v WOT. Those things,, although fed through a 5v reference, will notoriously get carbon tracking on the grid giving an open in signal return yet no CEL. And data is too slow to catch it.
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