Consistant mis-fire [Archive] - GrandAmGT.com Forum

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H.O. Driver
07-27-2011, 08:45 PM
So far I have replaced the coil packs, spark plugs, and wires. Whats next? it idle's fine, but the SES light flashes and it scans mutliple cylinder misfires. Ignition control module, or whats the next step, I don't want to keep throwing money at things and have it not fix it.

HOYS
07-27-2011, 08:58 PM
What are all of the codes? Any P020X codes? (I.E. P0203)

350rs
07-27-2011, 09:16 PM
take the ICM to be tested. if it comes back alright try a compression test. could be a number of things causeing misfire. Could even be a injector.

[ChaosweaveR]
07-27-2011, 10:16 PM
Check the compression in all the cylinders, it's possible a collapsed lifter may be a colprit in this.

H.O. Driver
07-28-2011, 06:42 AM
k it is cylinder's #1 and #5, when we are scanning it shows they consistantly misfire and the other code it throw's is map sensor voltage low. However if it is only running on 4 cylinders it would have low vacuum and cause the map sensor to read low. The coil packs were very rusty and could not make a conection, so I swap those and the wires out and it idles and runs a lot better but still throwing the multiple cylinder mis fire code, I wish it was because a cam, but yea, just a stock cam in it... I will keep plugging away.....

juanvan
07-28-2011, 02:02 PM
Did you replace the plate under the coil packs? that will cause misfires too.

H.O. Driver
07-28-2011, 06:42 PM
Did you replace the plate under the coil packs? that will cause misfires too.

I did not, but that would be a good culprit, the terminals on the coil packs were pretty rusty and the the screws that hold them down I had one or two rusty ones. I will have to check that out tonight...

Malaclypse
07-28-2011, 07:38 PM
Don't rule out injectors. Also don't rule out the MAP code. You may have an open wire in the fuel rail harness under the upper intake causing your issues here.

plastic_indian
07-28-2011, 08:24 PM
You may have an open wire in the fuel rail harness under the upper intake

Where? You make it sound as if this is a pattern failure, and I've not seen this before...

Malaclypse
07-28-2011, 09:15 PM
Where? You make it sound as if this is a pattern failure, and I've not seen this before...

Its not something that happens all the time, no. I've seen stranger things happen though.

This harness runs along the fuel rail, under the UIM. The reason I suspect it is because there are two cylinders misfiring and a MAP code. Those are all on the same side of the engine and attatched to the same harness.

A multimeter measuring resistance of all the circuits going to the pass-through connector for that harness would tell the story. It may also point out a faulty injector or two.

H.O. Driver
07-30-2011, 02:01 PM
not sure what happened, pulled the coil packs off and check the plate under and it was fine, put it all back together, hooked up the plug wires and it fired up and runs fine, no codes no nothing! Not sure WTF was up it's butt, but I am guess maybe something with a coil wasn't making good contact or something, but it is running now, just got a flat tire, yea! No one around has a 245/40/18 in stock and the stock rubbers have dry rotted to the point of holding no air, so I guess it is a donut untill tuesday or snow tires, yeah :(