Misfire Blues

[2003MOPAR]

I have a question that I already know the answer to... I think I know the answer anyhow. My 2003, 4.7L with 99700 miles has been throwing P0302 for a while now. I have been clearing the code with my programmer. Now it's time to SMOG it and I think I'm screwed. The SMOG test failed because the ECU remembers codes that have been cleared recently - such as the code I just cleared prior to taking the truck to the smog check station.

After eliminating the usual suspects (plugs, COP) I have found the compression for #2 at 117 pounds. The other 2 I checked (1 & 4) came in at 140. I ran Seafoam through it in the hopes that a valve was getting jammed up with carbon deposits. I had fun and my truck smoked like it was on fire (someone actually drove up to see if I was OK) but I'm still getting P0302 after all of that.

I am curious to know if the dreaded lifter problem could be the culprit. The motor has always been noisy as far as the lifters are concerned and I haven't noticed any increase. The motor runs fine too, no stalling or shaking, just a weak/tired piston.

Since the motor only has 100K miles I am hesitant to pronounce the truck dead just yet. I am considering popping the valve cover just to eliminate the lifter as a potential problem. I don't have a good feel for the symptoms of a missing rocker but I bet they are readily noticeable. Has anyone noticed low compression and then found a bad rocker?

What do you think?

 

[2003MOPAR]

This is a followup question I suppose. If I do pop the cover and discover nothing wrong... Now what? Is there a definitive test to point to the bottom end vs. top? My feeling is that the engine is toast to me if it's on the bottom but I may have a fighting chance if it's top.

 

[RonJon '06]

If the top end checks out ok you can try using a borescope to inspect the inside of the cylinder. When I had low compresdion on a cylinder on my 5.7L there was a visible wear pattern on the bottom of the cylinder wall from metal getting inside the engine.

 

[2003MOPAR]

If the top end checks out ok you can try using a borescope to inspect the inside of the cylinder. When I had low compresdion on a cylinder on my 5.7L there was a visible wear pattern on the bottom of the cylinder wall from metal getting inside the engine.

Thanks for the suggestion. I really hope this will be a simple fix. It's a great truck but I don't have the $$$ to repair/replace an engine. Ugh.

 

[2003MOPAR]

Happy ending. I ran Seafoam through it. No more codes and it passed SMOG. I plan on checking the compression again just to see what the difference is.

My truck is going to LIVE !!!!

 

[ramirezcf619]

Happy ending. I ran Seafoam through it. No more codes and it passed SMOG. I plan on checking the compression again just to see what the difference is.

My truck is going to LIVE !!!!

So you ran seafoam AGAIN and it fixed your problem?

I have the exact same issue on mine. It runs great, lots of power. I'm just wondering what happens if I keep running the truck like that? Other than the CEL being on(random misfire), the truck runs great great. I do get the tick at startup then it goes away after about 1 minute.

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[ramirezcf619]

A little history on the truck....

2003 with 5.7L
I bought it used with 125k on it. Didn't pass smog because when the smog guy floored the pedal there was a lot of smoke visually coming out exhaust. Told me he couldn't pass it. Took back to dealer that sold it to me and they looked into it. After about 2 weeks l, got the truck back with resurfaced heads and new gaskets, new water pump, new alternator and new radiator. Got back to Cali (truck purchased in Arizona) and passed smog the Next day. Day 2 though, I got the CEL FOR Random misfire. I replaced spark plugs with the champions copper, and wires, and coil packs. Still have CEL. I also have leaks from the bottom of both heads. The guys that worked on my truck must have overtorqued and pinched the gaskets. I definitely don't want them to work on it again.

Anyways, overall it's been a poor experience with this truck but it's financed and want to get as much out of it before I need to put more money into it or replace it. So from my previous post on this thread, I am wondering if I can keep running the truck like that? I don't really want to use seafoam due to already having leaks. I don't want to make them worse. Will seafoam make my leaks worse? They are not too bad right now.
But if seafoam could fix my misfire and not make my leaks worse, I am willing to try it. Thanks for any input.

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[2003MOPAR]

I only know what I've seen as far as Seafoam is concerned. It cleared out enough carbon to make it run better. I have been free of misfire codes ever since and the code had persisted for years prior to Seafoam.

 

[ramirezcf619]

I only know what I've seen as far as Seafoam is concerned. It cleared out enough carbon to make it run better. I have been free of misfire codes ever since and the code had persisted for years prior to Seafoam.

Thanks. I'm gonna give it a shot.

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[2003MOPAR]

From what I have learned about Seafoam there are 3 areas that get treated: Intake through exhaust, motor oil, and fuel system. I added the suggested amounts to the oil and fuel tank and then sucked the remainder into the intake via a vacuum hose with the motor good and hot. I did run Seafoam through the intake twice a few days apart. Maybe i was a little impatient but the codes have stopped for good since I ran that last can through.