2001 LS cold misfire, back at it again!

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twistedwrench

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So after sitting in storage for the winter I'm back at this cold misfire situation. Figured I'd go back to basics and start with a COP stress test, injector pulse width test, cylinder balance test, and compression and leak down tests. I got an interesting result, which I'm not 100% sure what to make of, I feel like the rings are maybe a bit worn, but, maybe they are really crapped up. Cold compression test results 185, 195, 80, 180, 195, 195, 180, 175. Hot test results 195, 205, 175, 190, 205, 205, 195, 190. 1 tbsp oil in #3 cold 140 psi, hot 205. I find it interesting that the cold compression is 100 psi off, and oil in #3 cold does bring compression up 60 psi, still way under acceptable, but just letting the engine warm up brings dry compression to 175 psi. For now I'm going to try soaking cylinder 3 with sea foam, and see if it maybe frees the rings up. If not......engine disassembly is in my near future....and honestly...look at those numbers, who am I kidding, this thing is most likely coming apart.
 
So after sitting all night and drying the cylinder out I have a slight improvement 110 psi on #3 cold....!@#$, !@#$, !@#$, and @#$ 150 psi wet, 190 hot... So Ok hot is totally acceptable, I didn't even bother with a wet test hot. cold is better but not at all good. Some trick work with a led light and 2 mirrors(who needs a bore scope?), revealed #3 is very smooth inside the bore, almost no cross hatches, while 1 and 2(couldn't see into 4) have pretty well defined cross hatching. So.....Engine Restore.....who has any experience with it?, is it as good as they say?, will it delay my inevitable engine rebuild? I'm on the fence over trying it, I'm not a believer in "snake oil", but I know from experience Sea Foam is amazing, MMO can work wonders on stuck or sticky rings. I know it's not a real fix but I'm honestly thinking about trying it, if just cleaning my rings got me 30 psi cold compression, and my compression is now building to 190, after only a few minutes of run time, maybe it can delay a rebuild for a while, a total tear down for low cold compression in 1 cylinder just seems like making a mountain out of a mole hill. Though I have priced the parts and with the exception of the 2 days of labor it's only roughly $400 to tear into this and hone all the cylinders and do rings and the top end gasket kit. Thoughts, and/or experience with restore would be awesome.
 
Well, I let the LS sit with sea foam in #3 for another night, dried it out, and retested again, 115 psi, pretty much no gain since yesterday. Put it all back together and put Engine Restore into it. This stuff says 500 to 1000 miles to take effect, 1 hour at an idle running a cylinder balance test I've already noticed the spikes smoothing out. I recorded yesterdays balance test, and compared, cylinders 1, 2, and 8 are almost exactly the same(they looked really good yesterday) the rest of them including #3 have far power drops 4, 5, 6, and 7 have about 30% of the power drops they had yesterday, and 3 is actually showing steady with no drops. I'm not sure where my compression is at yet, and I'm going to let this stuff do its thing for a few miles, and retest cold compression. Fingers crossed and I'll let you know how it works out.

P.S. This car has always had a slight bit of white smoke when running, I figured it was valve seals leaking a little. 30 min after I put the Restore in it completely stopped smoking. I'll keep an eye on it and see if it smokes when I start it in the morning. Usually it's a quick puff of white smoke about the size of a basketball and a light stream while running coming from each tailpipe.
 
Started it this morning, still a slight misfire, and a tiny wisp of white smoke out the tailpipe. No white puff like usual, that's a nice side effect. Didn't even make it to the end of the driveway, misfire stopped, usually takes until the stop sign. Jumped on it, tires spun, and it hesitated, and I though oh no! Oh...turn traction control off..... Jump on it again, burned the tires nicely >:). I couldn't tell you by a seat of the pants, feel of power, but according to my meter it's running better. Drove it about 15 miles, and this thing is running SMOOTH, I stopped at TJ Maxx and it was running so smooth I couldn't even tell it was running. The wife even commented on it, and it had completely stopped smoking by then also, not even a little wisp. I haven't done a compression test yet, but I've only done 30 miles and an hour of idle time since putting the restore in. So I'm going to run it as much as I can for a few days before taking compression again.
 
Day 2 after putting restore in, started the car, no puff of smoke, actually took about 15 seconds for the slight stream to start, misfire was gone before I got out of my parking spot. Since I've had the car this misfire hasn't gone away that quickly ever. Best I've had is about a minute, it was under 30 seconds today. Again by the time I got to where I was going the car had completely stopped smoking. Also it is noticeably smoother when running after warming up when the misfire is gone, stopping at traffic lights I can't even feel a slight vibration, prior to putting the restore in I could feel a slight vibration in park or neutral, and I could really feel it sitting at a stop light. Misfire still isn't cured but the smoking stopping and the engine idle smoothing out is kind of nice. And the bottle does say 500 miles to see a change, I've done 70 miles or so....
 
Did I understand correctly, you had Sea Foam in #3 but the Engine Restore went into the fuel tank?
 
RigsLS said:
Did I understand correctly, you had Sea Foam in #3 but the Engine Restore went into the fuel tank?
Click to expand...

All such products that I have seen, are added to the engine oil.
 
I put Sea Foam into cylinder #3 overnight to clean any buildup on the rings. The Engine Restore goes into the oil, like Joe said.
 
10 4,
Heard of it, seen it on the shelves, never used before. Sounds like positive results.
 
Ok so started it today, no smoke what so ever, misfire stayed for 2 minutes, and I've discovered something. If I start it put it in gear and give it a little gas misfire goes away, if I start it and let it idle misfire stays for about 2 minutes. Saturday I should have a little over 100 miles on it since putting in Restore, it did stop the smoking, and its running smoother than ever, but it seems to have done very little for the misfire.. then again, I'm not even 100 miles into it. Time shall tell.
 
Possibly an intake leak?
Propane test it.
 
Already did a propane test, with the scanner attached. I know it's a compression issue in #3 I'm just trying to delay the inevitable rebuild. I'm not going to tear this thing down and do a backyard job hone 1 cylinder and 1 set of rings. When it does come apart it's getting an overhaul, All new gaskets, rings, bearings, timing chains, and tensioners. With some luck I can hone it over .002 or less and just get rings, as long as #3 isn't too bad and the piston lands aren't trashed.
 
I take it you are mechanic by trade?
Good luck with all that, rest of us chumps would just get another LS :D
 
I used to do fleet maintenance, it's been a long time since I rebuilt an engine as small as a 3.9l . It might be fun to rebuild a gasser, instead of a diesel with a 400lb crank shaft. And my small cylinder hone, and my snap on cylinder bore gauge haven't seen action in like 12 years, they're due for some.
 
twistedwrench said:
I used to do fleet maintenance, it's been a long time since I rebuilt an engine as small as a 3.9l . It might be fun to rebuild a gasser, instead of a diesel with a 400lb crank shaft. And my small cylinder hone, and my snap on cylinder bore gauge haven't seen action in like 12 years, they're due for some.
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So you are convinced the engine restore helped? Any risk to using it?

I too just put my '03 LS V8 back in to action after sitting in the garage for about 2 years. Had the misfire as well, replaced all 8 coils which seemed to clean it up greatly. I still feel a little shake at times while idling, nothing significant. Am always open to anything that improves the smoothness.
 
The Engine Restore helped the smoking from leaking valve seals, and smoothed out the idle, but so far has done nothing for the cold misfire. The bottle does say 500 to 1000 miles before I will see improvement, and I've only done 100. I will give this stuff props in 100 miles it completely stopped the smoking, now it doesn't smoke at all, and a definite smoothing out in the idle. Only time will tell if it will help my compression on #3. At this point if you have a slight vibration, and no solid misfire, I'd run Sea Foam in the gas, with some high octane fresh fuel, and a bottle of restore could smooth that idle out a bit. 2 years is a long time for a car to sit with ethanol fuel in it. The fuel goes bad and varnishes the entire fuel system. I either use marine stabilizer (the red stuff for ethanol fuel) in anything that's going to sit longer than 90 days or drain the fuel system.
 
twistedwrench said:
The Engine Restore helped the smoking from leaking valve seals, and smoothed out the idle, but so far has done nothing for the cold misfire. The bottle does say 500 to 1000 miles before I will see improvement, and I've only done 100. I will give this stuff props in 100 miles it completely stopped the smoking, now it doesn't smoke at all, and a definite smoothing out in the idle. Only time will tell if it will help my compression on #3. At this point if you have a slight vibration, and no solid misfire, I'd run Sea Foam in the gas, with some high octane fresh fuel, and a bottle of restore could smooth that idle out a bit. 2 years is a long time for a car to sit with ethanol fuel in it. The fuel goes bad and varnishes the entire fuel system. I either use marine stabilizer (the red stuff for ethanol fuel) in anything that's going to sit longer than 90 days or drain the fuel system.
Click to expand...
Thanks!.
 
So, after driving it for a bit, the misfire has slowly been getting worse, and it now has a slight misfire when warmed up, not just when it's cold. So I've stopped driving it, and will be ordering an overhaul kit, no avoiding pulling the engine. Its getting a tear down, hopefully just needs a hone and new rings, but while it's apart, I'm putting all new seals and gaskets in. I'm also going to make a video, so people can see how to pull the motor the right way. I watched a video and cringed as they tried to pry it out the top. It's like videos of people cutting the crossmember to do an oil pan in a 7.3....you can do it that way....but I don't recommend it.
 
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