P0302 Issue again 01 Bonneville SSEi - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 07-01-2011, 08:03 AM   #11
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You will need new rocker bolts. I suggest reusable. And I think those are like 23 foot pounds or there abouts.

I have not seen a bad UIM gasket cause this, but I guess always possible.
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Old 07-01-2011, 11:29 AM   #12
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I HAVE noticed that it sounds like the exhaust has a bit of a leak. I replaced the catalytic converter about 2 years ago due to the element inside being broken loose and rattling. I've noticed a similar rattle coming from the CC but not as pronounced as the first time. Could the leaking LIM gaskets cause enough coolant to get into the exhaust that maybe it has damaged the CC? Or even clogged or reduced the flow of exhaust enough to cause my misfire problem?
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Old 07-02-2011, 12:41 PM   #13
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Okay, here are the results of the compression test:

#1--149
#3--147
#5--144
#2--147
#4--145
#6--151

I would say that the piston, rings, valves, and head gasket are good. I also check the hoses after closed loop so that the coolant was fully circulating. I figured that if combustion chamber gases and pressure were leaking into the coolant passages, they would be pressured up. They were their normal firmness.

This leaves me with either the broken spring, collapsed lifter, bent pushrod, air leaking around the new injector and injector seal, or a bad CAT. I went ahead a replaced all the spark plugs again just in case I had defective one. No change.

After running the engine for a while, I pulled all the plugs once again. The #2 plug had a heavy fuel smell. No real discoloration either, but of course the plugs were only about an hour old.

I'll pull the Supercharger off to get at the real valve cover and check the springs. If I don't see a bad spring, then I'll take the lower manifold off and check the lifter and push rod. If THOSE are good, guess it'll go to a muffler shop to have the CAT checked.

`
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Old 07-02-2011, 12:55 PM   #14
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Compression looks OK.

A wet plug indicates bad fire. A leaking injector O ring wont cause that because it'* in the head before the intake valve.

You should be able to tell if you have a bad lifter or push rod from the top. Look for a loose rocker.

If the cat was the problem, I would expect more then just one cylinder to show this problem. It'* something unique to that cylinder. So lets look at what it isn't. The plug is wet, so injector is good. Check the springs, to confirm or rule out. Plugs have been changed, so not likely that is the problem. I would try swapping #2 and #4 plug wires around and see what happens. Same problem with #2, then move on to coil, swap coils. Problem still there. It can be the ICM. I've seen a few times now where one cylinder is effected by a bad ICM.
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Old 07-04-2011, 05:20 PM   #15
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I was able find an O'Reilly with a working ICM testing station. It passed the test twice and failed once. In my opinion, my ICM is good. I could be completely wrong too. It'* just that I already tried a new ICM with the same #2 misfire. I swapped the new #2 injector around to the #1 position thinking maybe it is something unique to the injector,I.E diameter or sealing surface. Same thing, #2 misfire. I swapped 2 coil packs around again to see if maybe it was them. Nope, #2 misfire.

I am going to go have the CAT checked out tomorrow sometime. I feel the same way about if the CAT IS bad, it would affect all the cylinders. I am trying to exhaust all options before I have to drain all that new coolant and replace gaskets again. I'* just a real pain in the butt to get at that rear valve cover without taking the supercharger off.

Maybe I can sweet talk the people at the O'Reilly in town to let me test a new ICM on my car in the parking lot. That seems to be my last easy option...other thatn having the CAT tested.

IF it passes these tests, i'll pull the top of the motor off again.
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Old 07-04-2011, 05:27 PM   #16
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Quote:
Originally Posted by Danthurs View Post
Compression looks OK.

A wet plug indicates bad fire. A leaking injector O ring wont cause that because it'* in the head before the intake valve.

You should be able to tell if you have a bad lifter or push rod from the top. Look for a loose rocker.

If the cat was the problem, I would expect more then just one cylinder to show this problem. It'* something unique to that cylinder. So lets look at what it isn't. The plug is wet, so injector is good. Check the springs, to confirm or rule out. Plugs have been changed, so not likely that is the problem. I would try swapping #2 and #4 plug wires around and see what happens. Same problem with #2, then move on to coil, swap coils. Problem still there. It can be the ICM. I've seen a few times now where one cylinder is effected by a bad ICM.
Is there anything unique to the harness running to the ICM for that particular cylinder? I guess what my question is, is there a dedicated circuit related to that cylinder in the harness? I also checked the bundle of grounds attached to the front cylinder head and the one single ground sandwiched between the two nuts on the stud for the SC belt tensioner assembly. They both read 0.8 ohms.
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Old 07-04-2011, 05:27 PM   #17
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Have you swapped plug wires?
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Old 07-04-2011, 05:34 PM   #18
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The fire signal comes to the ICM from the crank sensor, the ICM knows what coil to fire. You have a waste spark system, so both cylinders fire at the same time. So a single cylinder misfire is most of the time not a bad coil, but can still be a bad post. A bad ICM is again, generally both cylinders on that coil. I believe you have already ruled those parts out. So unique to each cylinder is where you need to start looking. Plug, plug wire, injector, and injector harness. You have swapped injectors. So that'* out. The plug is wet, I say that rules out the harness, but you can still test it with a light. Now we are down to a bad plug or bad plug wire. I suggest taking the plug out, disable the fuel pump. Put the plug in the wire and lay it on ground. Crank and make sure you have spark. I'm guessing you do, but willing to bet it'* weak. Test the plug wire. Once that is all done, as I said earlier, your in to mechanical problems, ie, a broken spring.
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Old 07-05-2011, 06:18 PM   #19
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Okay, I have torn the top end off once again. On the #2 cylinder, both springs are intact. I have physically run my finger and a cloth rag around each coil cpring to see if there were any burrs or cracks that would catch the rag threads. Nothing. Pulled out both pushrods and rolled them across a flat surface. No bends. As for the lifters, I figure they are good due to the results of the compression test.
Rockers look fine too.

SO this pretty much takes me back to square one. They only real variable that is still sort of an unknown is the ICM. I passed twice and failed once on the testing bench. But even with 1 new replacement put on the car, it still gave me a #2 misfire. But, the broken test bench at the first O'Reilly said it was bad too.

Please tell me I'm not an idiot and mistaken the left front cylinder for another cylinder. The cylinders on the right side of the block with the timing chain in front of me is from front to back 1-3-5. The cylinders on the left side of the block with the timing chain in front of me is from front to back 2-4-6.

Hopefully I'm not a complete jacka$$ and have been working on the wrong cylinder.

Is there anything else I should check for? Maybe blow out the injector rail assembly, swap the the fuel pressure regulator, insert stick of dynamite and grab a beer...or two?













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Old 07-05-2011, 06:25 PM   #20
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#2 is the rear head by the alternator, and it looks like that is where you are. Only other thing I can think of is a chipped piston. You would need a bore scope for that. A compression test wont show if you have a chipped piston.
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