Tahoe_Sport

I've been having problems with my engine misfiring for the last year. I've taken it to three shops for them to figure out what is wrong. The first chevy place said all it was was the timing and they adjusted it. That did not fix it. The second chevy place said it was the injectors. Still haven't gotten that fixed because I was going to have them cleaned first to see if that worked. At the shop that was going to clean the injectors they said I need a new engine because coolant is leaking into two of the cylinders. Do I really need a new engine or can this be fixed?

vwrabbitgtd

Well, the big indicator of coolant leaking into the cylinders is either blue smoke out the exhaust or the constant battle of keeping your coolant topped off.-- if you don't have either of these 2 symptoms, I'd say they are wrong. When I had the diagnostics done on my 92 350 TBI, it was knocking and was obviously a rod or main bearing, they still told me it was a bad head gasket-- I'm beginning to think that is the standard answer instead of just saying "we don't know!"

In all my years of driving and working on vehicles, I have found that the plug wires are the #1 cause for a miss. Even if I find a bad plug, etc, etc, it always sources to be the plug wires. I'd replace them before getting too excited on tearing into the motor.

sreve

intake gaskets leaking coolant is very common on these engines. usally they are external leaks. an internal leak (small) can cause a miss.coolant in the oil or a hydro lock can be the death of an engine.
do you have a P0300 or P030x X being a number from 1 to 8 ?
any drivability problems? or run ok?
mifire monitor is senitive to protect the cat.

jveik

yeah i wouldnt think misfiring would have much to do with the lower end of the engine, or even the water problem. if there is water in your cylinders, you prolly get white steam coming out the exhaust? anyways, the misfiring could be a lot of things not needing a new engine necessarily. if it dont burn excessive amounts of oil, its probably ok. maybe the valves arent seated right or are floating? camshaft could be worn excessively, distributor or wires, lots of little things can cause it. one time my buddy had all 4 wires on the right bank melt the insulation and short out to the exhaust manifold, the blue smoke [bad engine ] only came out the left pipe of the dual exhaust lmao

make sure to get the problem narrowed down and dont just throw money at it. it could be a matter of a 200 dollar camshaft versus a 2000 dollar crate engine lol.

Crasen

I would have to say the first thing I ever do is replace the plug wires for a missfire. Spark plugs can easily outlast a set of wires, especially if they are platinum plugs. The injectors could very easily need to be cleaned. If they use an ignition scope they would be able to see it on the spark pattern. If there was coolant leaking into two of the cylinders I would say they found two cylinders failing a cylinder leak down test and boroscoped the engine an noticed the two cylinders that were failing were significantly cleaner than the others, but that would make me think more of a head gasket. But if you have been leaking engine coolant for a year you would more than likely already know that. If you have a check engine light I would get the codes read at auto zone or somewhere like that, if not I would try plugs and wires, you wouldn't want to put old plugs and wires on a new engine anyway

GMMerlin

Well lets do this first before we start jumping to conclusions.
When does the engine misfire? Be specific

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LastOne

I have had this for years on my 98 350Vortec. It will miss under load or going up steep hills. Been through electrical and fuel system. Turns out there is a "known" problem amongst GM mechanics that a condition called Mechanical Sticking in the heads . Basically there is wear and or poor lubrication and the valves stick a bit. I switched to Mobil 1 Full Synthectic oil and it has all but cured my driveability issue. In heavy stop and go traffic I will post a cat inefficency code but no more random misfires at all. It took the Mobil 1 about 2500 mikes to work. I have been miss free for a year. On the hwy with no A/C running I get 19MPG at 75MPH with the windows up. Truck has 109K on it. Intake manifold gasket replaced after the "miss" symptom arrived. Not sure if they are in common but try switching to pure syn oil and see what happens. Cheaper than reworking both heads. FYI, compression in each cyl was 180-185PSI with 95K on the motor.

wilfie27

FYI these heads are prone to cracking either the center head bolt hole or from the exhaust valve seats. Probably 1 out of 5 are cracked.

wafrederick

The timing is not adjustable.The miss might be caused by a worn out distibitor gear,a common problem