Engine has a miss at idle exspecially in the morning
Have a 2002 tahoe with 84000 miles last year i noticed a rough idle in the morning when i started it the sevice engine soon light would flash but when started driving it went out and the truck would be running better but still had a hesitation at idle or sitting still.i changed plugs and wires and gapped plugs at the right specs.nothing worked.then i put a maf sensor on and thought it fixed it but the weather had just got warm and besides the little miss it was running better untill it just starting getting cold again now it started again finally i had the engine light stay on and got a code 0174 i put spark plug gappers on the oxygen sensors and cleared the code nothing again.just today i changed the plugs again and gapped them at the called for specs,there was a wet reddish yellow tinted substance on the first 2 plugs on the drivers side. once again still have the faint miss sounds like it could stall but dont. it seems 2 run a little smoother but the miss is still there. any suggestions would very much be appreciated. im out o f ideas only thing else i can think of is the intake plenum gaskets.
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Would it give you any more room if you removed the front wheels and worked through the wheel well? You would need an extra long extension to go on your ratchet. The check engine light is probably caused by the rough idle. If you had trouble getting the plug wires off due to the cramped space, you may not have gotten them back on good, which would cause a miss and a rough idle. I have noticed that many times, when I install a new set of spark plugs, the engine will tend to have a slight miss at idle. This usually happens to engines that have not been tuned up in years. I always attributed it to combustion chamber deposits being burned of by the more complete combustion of the air/fuel mixture from the new plugs. It usually goes away after a couple hundred miles of driving, especially at highway speeds. One thing I like to do to an engine that has high mileage is run a can of Marvel Mystery Oil through the intake at very high idle. You would have to use a small vacuum hose inserted into the can and hook it up to a vacuum source so the engine can pull the oil in through the hose. It it was a carbureted engine, you would just pour it slowly into the carb. If you do this, ve sure the vehicle is outside with plenty of ventilation. Once the Marvel Oil starts burning in the combustionchambers, there will be lots of white smoke pouring from the exhaust pipe. This is normal, and it will clear up once the oil is no longer being fed to the engine. The Marvel Oil will clean all the deposits off the combustion chambers and also the top of the pistons.
It's called piston slap, what happens is that when the engine start to get a few more miles in it's life. The clearance between the piston and cylinder walls are greater then when the piston are warmed up and has expanded.
You can add Lucas oil treatment to you engine oil to put a film of oil along the cylinder walls, so when you start the engine there is a coating of oil there that will help your engine to last longer. Just follow the instructions and try not to drive the Tahoe until the engine has warmed up a bit, the winter will be more noticeable and will take longer for the piston slap to go away.
Gm has a up graded program to address the piston slap to help make the engine last longer. Believe it's covered under the TSB if you bring it in to have it addressed. The program simply turns the timing back on the engine when it's cold to help eliminate most of the knocking and is helpful in making the engine last longer. As the engine warms up, the program brings the timing back to where it should be to not economy and performance is lost.
Thank you for using fixya and good luck.
A tune up will not cure the lean code, in fact an engine miss gives a rich code from the unburned fuel. I would suggest u verify u have no vacuum leaks, also clean the inside of the MAF sensor if so equipped and replaced the bank two O2 sensor, that is the passenger side sensor before the catalytic converter. If u have the money replace both right and left sensors, it is better to do them in pairs.