P0304 Misfire on 1997 GTP

[Keith1951]

I just read the post where BillBoost says to swap #4 and #1 plug wires to see is the misfire follows the coil. I did that and ran the car for 5 minutes and never got a misfire code ( I'm still getting my nagging P0171). Can you tell me where to go next?

[Fivefingerdeathpunch]

I'd try and find the source of the vacuum leak, that is what the P0171 code is for.

Swap injectors is another thing to try for the misfire, swap the coils themselves to see if the misfire follows. Swapping wires doesn't make sense because cylinder one is on the front and 4 is on the rear.

[jesseC651]

Did the miss stay?

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[Keith1951]

The reason for swapping 4 and 1 is because they are the same coil pack. I'm still looking for the vacuum leak. The miss went away when I swapped coils but I'm not sold on it being gone since I still have the P0171. I am afraid that as soon as I get rid of the vacuum leak, the misfire will come back. (Murphy's Law!)

[jesseC651]

Have a spark tester?

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[Keith1951]

No but I have access to one. I keep reading that the P0171 can cause all sorts of problems and is caused by various things so I'm going to replace the EGR Pipe today and if that doesn't fix that I'll start replacing vac lines I hope once the P0171 goes away so will the P0304

[jesseC651]

Smoke test it first

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[Keith1951]

Yeah that's what I'm thinking. I've done the brake cleaner spray all over the thing and can't get it to change rpm's

[jesseC651]

That don't work good

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[Keith1951]

It's Gone!!! I found a hair-line crack in the EGR Pipe under the mounting clamp on the EGR end. I replaced the pipe and the P0304 and the P0171 went away

[jesseC651]

That would make it run like **** under boost ?

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[Fivefingerdeathpunch]

Yeah, any leak vacuum leak or exhaust leak like that can make it run bad.

[Keith1951]

It will make it run like**** all the time! At least mine did and like BillBoost said, it doesn't show up when you do the brake cleaner trick. It might when youy smoke test it but I never got that far.

[jesseC651]

We made a fog machine work to test for leaks we found the egr tube was bad in like 5 mins

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