V6 Tech 1967-2002 V6 Engine Related

Frustrating problem, need help!

Old 10-22-2012, 09:23 AM
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Frustrating problem, need help!

I need some help, car is driving me nuts! I have a 99 3.8 5 spd

So for a few weeks the car has been having an issue where at high rpm's and acceleration (3700 rpm or greater) the car misfires, it feels like hitting the rev limiter. It does happen in 1st gear, only in 2nd and higher under load. Its as if I have a new rev limiter at ~4000 rpm, car cant go higher. Its not something that happens often since rarely do I accelerate that hard but you have to keep it in mind when trying to accelerate in highway such as trying to merge in, I could find my self hitting a wall.

So first I figured it was spark plugs or cables so I changed them. Plugs were in good condition but went ahead and put ac delco rapid fires anyways. One of the cables was busted so I installed a new set of Bosch. I though this would fix it but problem persisted just as before.

I then checked the coils and one of the coils was also busted so I changed them all, but again the problem persisted.

My next guess was the ICM, luckily my brother had an extra module that had been tested in his car and worked fine. So I changed the ICM for his and again nothing. Still same exact misfire.

I am really frustrated, I essentially ruled out the entire engine spark system so it cant possibly be there. I doubt it is injectors because Torque is telling me all cylinders are misfiring. Also, computer is not giving a check engine light at all.

I don't know what the hell could be wrong, so frustrating! My brother suggested the fuel pump so I checked the pressure with a gauge and was reading 42 PSI, seems a bit low from spec but not sure if this alone could cause such a problem. Don't want to spend another $300 on a fuel pump to find out the problem is still there. FYI fuel pressure regulator is fairly new, less than 2 years old.

Any ideas or suggestions?
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Old 11-03-2012, 09:38 PM
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Re: Frustrating problem, need help!

I've never hear of anything like that, might as well just take it to a mechanic and pay the $80 or whatever to have it diagnosed. Maybe the cam posistion sensor or something like that is bad and the engine thinks it's running redline when it's really not. Or maybe your tach is just wrong. A shop with a real diagnoses machine can see things you cant with the cheapo from autozone, those Snap-On diganosis computers are $4,000 for a good reason.
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Old 11-04-2012, 06:05 PM
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Re: Frustrating problem, need help!

check the great misfire mystery thread on the stickies in this section.

Make sure your wires are not grounding out against your exhaust manifolds.

My suggestion... run the **** out of the car until you get the flashing SES light, then take it to a parts store and have them pull the code, they will tell you what cylinder is misfiring, check it out, and consider swaping coils around if you are confident on your plugs and wires. Even go as far as swapping a plug/wire and see if a new code pops up on another cylinder and that cylinder goes away.
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Old 11-17-2012, 10:04 PM
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Re: Frustrating problem, need help!

Sounds like a bad sensor to me. Could be any of them -- MAF, knock, cam/crank position, throttle position, IAT... basically any of those could be beginning to fail and could cause the symptoms you're describing.
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