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Misfires, overheating, oil dripping out tail pipes


wade9047

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A little background: Im learning as i go here so bear with me. My 5.3 Silverado (has 195000 miles on it but very well maintained until the last couple years I got somewhat lazy about it). Over the course of that time I stated losing some balls on the low end and hearing a faint fluttering noise coming from behind drivers side dash when accelerating. It was annoying but reliable so I didn't think much of it.. and boy it's thirsty for oil. I never find leaks beneath my truck and I would get an oil change every other month as well as adding a quart in between changes. I have shorty headers on it and no cats and 3 inch pipes (wish I stayed with 2 1/4).

 

Heres where I'm at: its running rough at idle and throwing PO300 codes. Misfires were occurring on all cylinders but mostly on two of them (cylinders 7 and 8 misfires over 1000 times over the course of 100 miles, the others arent misfiring nearly as much). I found this out after taking it to a shop after it randomly overheated and shut off a couple of days ago. The coolant looks like my baby's diaper and was a little low but no obvious leaks. They did pressure test, sniff head and checked for leaks, but found nothing. I feel stupid to admit but I've had this truck 3 years now aND I didn't know you needed to change out the coolant.(I plan to get it flushed out when I can). I will get it compression tested today and I will probably do a tune up on it just to be sure (replace at least plugs/wires, fuel and air filter, etc.) In the past year or two it seemed to burn a lot of oil, but this trick always did and ran fine. But now im getting what i think is oil coming out of the tailpipes and little white puffs of smoke (Sometimes at idle but almost always when accelerating.)

 

I guess the elephant in the room that I'm trying to ignore (or at least put off) is an issue with a burnt valve or leaky head gasket. It seems like I have to play the game of tear the engine down or fix everything until it's better. Hopefully that wasn't confusing, but I can clarify if need be and the compression test I'll get done today will obviously help out. Thanks for any help.

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Sounds like you have the castech heads and oil is getting into the coolant. Do a search on here for castech you might be able to get away with getting new heads.

 

What year model is it?

 

 

Sent from my MaxiPad

Its a 2002 5.3 4x4.. even though it has almost 200,000 miles it has a ton of work done on it (more than I understand or even know). I bought it from a good friend of mine 3 years ago. Hes got a shop and basically bought it for cheap years ago and fixed it up. I know its programmed and has stuff like aftermarket heads, throttle body spacer, upgraded gears for the big ass tires and things like that. It was flawless when he sold it to me but I am not a truck guru so I kind of let it go for a while. Now it seems there's so much going on that I can't even figure out where to start. Other than a head gasket issue, I feel like it could be a vacuum problem, a fuel problem (my pump is screaming) or maybe as simple as an ignition problem. They called me from the shop I just took it to a few hours ago and said that they were likely gonnna have to replace plugs and wires just from doing the compression test, which I know doesn't hurt to do anyway. The only thing I have messed with since I got it is putting shorty headers and a new exhaust system on it. That was two years ago. I did have a plug and wire go bad a year or two ago and got it fixed but I can't remember if they replaced all the plugs and wires. Maybe they only did one cylinder and the rest are going bad now? Or is that not likely? The fact that its missing on all cylinders (two cylinders much more than the others) makes me want to think its a broader problem. But honestly I really don't know. I really hate relying on a mechanic I don't fully trust to start speculating.

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Sounds like that engine has reached the end of it's useful life. Compression increase after adding oil indicates severely (with those numbers) worn rings.

 

Cheaper/easier at this stage to just grab a boneyard engine with lower miles. Normally I steer clear of major jobs using junkyard parts, but with the year model and your miles, that truck probably isn't long for this world anyway, hate to say. Just judging from what I see up here - YMMV. If it's rust free and everything in the interior isn't failing (ripped seats, peeling dash, broken window regulators & door lock solenoids, heat / A/C not working properly, etc ... ) it might be worth dropping the coin on a new long block.

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Need to find out what's causing that misfire. My guess from here is probably head gaskets. Might be time for a crate engine - that would be the easy way out, but the most expensive.

 

I miss the days when GM could build an engine that would go over 400k miles and not burn a drop of oil ... :nonod:

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Sounds like you have the castech heads and oil is getting into the coolant. Do a search on here for castech you might be able to get away with getting new heads.

 

What year model is it?

 

 

Sent from my MaxiPad

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A little update... the plugs and wires were bad when they pulled them for compression test. They said the plugs had a brownish color to them and the engine was pretty "gunky". The compression test numbers are as follows:

C1: 165.0 /// C2: 121.0 /// C3: 83.5 /// C4: 81.5 /// C5: 89.0 /// C6: 156.5 /// C7: 111.0 /// C8: 120.0

They started a wet test but couldn't finish the last cylinder before they closed on Sat. The good news I guess is that they were able to build up compression to acceptable levels in all cylinders except the last one (which they hadn't got to yet). They suspected there could be an issue with a sensor on the engine (can't remember what they called it unfortunately). They still say they have no indication of anything else thats wrong without tearing down the engine (which would probably end up costing me as much as getting a used one with 100,000 miles less). I'll update when I find out more today.

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