1999 Grand Prix 3.1L Misfire even w/ new injector

Ive got a 3.1 with a misfire in cylinder 5. Ive had the plugs and wires changed, ive swithed the coils around to try to get the misfire in a different cylinder but its still in number 5. I just changed the injector and put in a new one. The check engine light still comes on and it still blinks when i accelerate. when i check the code with an OBDII, it has two codes both saying cyl 5 misfire detected! I have no idea what it could be, unless there is coolant getting in my cylinder? Any ideas????

Reply to
J-Dawg
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Is the injector getting the electrical pulse? Maybe there is a problem with the wiring. It needs to be checked at the injector and also at the computer.

Reply to
buickman

Well, if it isn't the coil. It could be the injector harness, or even the ignition control module.. OR you could take it to a shop and see if they can't fine the problem.

Reply to
clevere

Use a noid light ($5-10 @ autopart store) to check if the injector gets a signal. This doesn't check the timing of the pulse, but I would only check that if you rules out anything else. Since you changed the plugs and wires, that part is probably ok too. The next step is checking for a problem with your valves or piston in cyl 5. The easiest is a compression test, if that indicates the problem I would check for carbon build up (This would be fairly sure bet if it wasn't for the fact that you only have problem on 1 cyl and quite a few of them).

Don't wait to long because it might ruin your catalic converter and depending on the state you live in that might be a big problem.

Reply to
Simon

I have a 98 Montana w/3.4L engine w/104K miles. Around 95K miles the engine started running very rough and the SES light came on. I've got a unit to record engine parameters and read the code using a laptop. The code indicated a misfire in cyl. #5. The plugs had less than 15K miles, the plug wires were Taylor however that didn't mean that they were good. So I switch the plug & wires from #5 to another cyl. and the problem remained. I also, like you, switched the coil pack although if it were bad I'd think 2 cyls. would misfire. In any case nothing I did changed the fact that #5 misfired. The last thing I did was switch the injector from #5 to a cyl. in the front bank............ and lo and behold the problem cleared up......... for about a week! Then another cyl. misfired but not the one with the original #5 injector. In the end I ended up replacing all the injectors with a set of reconditioned ones for about $150 and the problem has not come back. Have you tried running some injector cleaner such as Chevron Techron?

Reply to
DonW

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