Werid missfire on #3

[richtazz]

Do you have access to a timing light? You can hook the inductive pick-up on the # 3 wire and aim the light at the underside of the hood to watch the spark pattern. This would finger or eliminate the secondary ignition system as the cause of the misfire. If the flashes are consistant, the ignition system isn't the issue. If there are gaps in the flashes, then it's definitely a spark related issue. That way, you can concentrate your efforts on mechanical or fuel related causes for the mis-fires if the spark pattern checks out.

[grandprix00]

yes switched the injectors around and did test all the coil packs and did a injector pulse test did that awhile ago and all of them looked good compression was like 155 on all of them its not just a top end swap put a cam in there but only gt stage 1 that shouldnt cause a missfire like that for that cam and ive rebuilt the whole motor everything is new on there and i did eveything too the book and did every test u can do when putting the motor back together i know thats build right.

about the computer isue sometimes they need just a little better tune and yes everything worked right with the stock motor. im just going to wait to make enought money for a dyno and tune for the car i think they can tell me more what going on there.

okay yah thanks never rly thought that about the timing light ill try that out today.

[maxwedge]

Not related to the misfire issue, but the inside bolts in the LIM should be sealed as oil can migrate up the bolt, in my own 98 3800, I had quite a puddle in there and was using about 600/qt, when doing UIM I discovered the puddle of oil, sealed both inside bolts now getting , 2k /qt, this is a 230k engine. I did not see a visible sign of oil fouling here but the ports were oily.

[grandprix00]

okay will do thanks

[tblake]

A rounded off exhaust camshaft lobe can give you adequate compression, but your car will missfire....Just a thought

[grandprix00]

yah its its got a new cam in there probably only 50miles on the new motor

[tblake]

Who installed the Cam? Just curious...

[grandprix00]

i did why?

[tblake]

I dont know, just thinking if it came with the rebuilt engine I'd wonder about it.

You did use engine assembly lube, right?

[grandprix00]

ah yah umm i rebuilt the motor my self at engine class in college i know i did everything right by the book there wasnt one thing i over looked

[tblake]

I dont doubt you at all, Just was wondering...

No idea about this one anymore, head scratcher.....

[pontiaccrazy]

i have a 97 gtp and my friend as a 98 gt and we both get misfires on #3 but the car is not actually misfiring. it must be the pcm

[richtazz]

Just a question, do you have a scan tool that can monitor misfires? If so, exactly how many mis-fires are we talking, compared to the other cylinders?