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Help Diagnose a Problem

I have a 1997 Grand Prix, 3.8L non-supercharged with 113K Miles. The car shudders, sort of like hestitates when I attempt to accelerate at

40 to 60 miles/hr speeds. We thought the shuddering was Transmission related... it turns out that about two weeks after the shuddering started, the car started slamming in gear and we replaced the transmission early this week, with a new Goodwrench one. Now with the new trans the slamming is gone but the Shuddering remains.

The SERVICE ENGINE SOON light just recently come on, my mechanic hooked up his hand held diagnostic computer and determined the problem as RANDON MISFIRING (based on the diagnostic code generated). He says we need to start by replacing wiring, plugs, coils and tune up (in this order) to eliminate the problem. A local dealer did the 100K tune-up at 95K mles and about a year back. Does anyone know what the problem may be?? Please help! Thanks in advance.

Reply to
NSS
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Bad spark plug wire(s) GW (again)

NSS wrote:

Reply to
Geoff Welsh

Does GM diagnostics not tell you which cylinder is misfiring?

I recently had to replace a spark plug coil on my Isuzu, and the diagnostic told me specifically which cylinder was the culprit.

Reply to
wrestleantares

If it werent random it probably would. Also it depends on the type of scantool. A Tech II would give missfire counts for all the cylinders. Also it depends on the year make and model as to how much information the ECM is set up to collect.

Reply to
Bonnevilles R Kewl

My '94 Bonneville had a random miss. It got hauled in on a wrecker today. I'll let you know the outcome. It has always had a "shudder." It feels like it doesn't downshift soon enough.

Gary

Reply to
GARY

Interestingly enough the "one-in-a-million" stories do surface often in the NG's, but MOST shudders are a misfire from a failing plug wire. GW

GARY wrote:

Reply to
Geoff Welsh

I have ruled out plug wires. I call it "nervous" like maybe the entire engine/trans/suspension is shaking.

Gary

Reply to
GARY

Reply to
Grover L Hammonds

My 94 TransSport had the same problem. I replaced the MAF and it APPEARS to have solved the problem. Will find out in the spring, as the problem was always worse towing the trailer. Took out my trans too

- but 295,000Km.

Reply to
clare

Make sure they didn't screw with the air cleaner, and disconnect the sensor from it.

Reply to
clevere

Did the dealer do wires? Sounds like a bad wire. Easy to check with ohm meter

Reply to
Tj

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