Thread: what is a burnt valve?

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Thanks DennyW! I would never have thought of the Cat but I know we need to check the fuel pressure. Maybe replacing the FI pump is a good idea anyway with 85,000 miles on the car. Any body else have an idea? DennyW usually has it dialed in and he may be the smartest guy in Illinois! I wish he was closer!

Don Shillady
Retired Scientist/teen rodder

DennyW, Thanks for that comment, it is worth checking out. I have been reading other stories on the Internet about 1992 Luminas and there are a lot of similar stories, some of which are due to the trans lock up stalling the engine by not downshifting so maybe a trans flush is in order but that doesn't explain the cutoff while running at 70 mph so I think your suggestion is worth checking out. The pump is inside the tank and is electric so it is a hassle to change but the external resistor should be easy to check. Your repair experience is priceless! The truth is that most of my experience has been in building modified engines, not very well, and then then not worrying about the fact that most of my rebuilds seldom made it to 50,000 miles now that I think back so the family car as a transportation device with high mileage is a bit beyond my experience. Even so am I right that the symptoms do not match a diagnosis of burned valves? If the valves were burned it would not run well at all? Note that these later models get pretty complicated and it will only get worse if/when hybrids become common. Thanks a bunch, you are a gem!

Don Shillady
Retired Scientist/Teen Rodder

Originally Posted by Don Shillady

Thanks DennyW! I would never have thought of the Cat but I know we need to check the fuel pressure. Maybe replacing the FI pump is a good idea anyway with 85,000 miles on the car. Any body else have an idea? DennyW usually has it dialed in and he may be the smartest guy in Illinois! I wish he was closer!

Don Shillady
Retired Scientist/teen rodder

Don, I agree with Denny. Put the vacuum gauge on it and go for a ride down the highway. If vacuum slowly moves lower and lower I think you'll find your problem in the exhaust system. The 2 things I've seen most are a failed (plugged) converter and more rare but it happens, a collapsed pipe. I've seen a few pipes that have a inner pipe and it expands inside the outer pipe, without any room to expand, it collapses into the pipe interior, effectively blocking off any flow. No flow out = No fuel in.... I think you'll find your problem by measuring the vacuum. My 2 Cents! LOL

Originally Posted by Don Shillady

DennyW usually has it dialed in and he may be the smartest guy in Illinois!

Don Shillady
Retired Scientist/teen rodder

OMG Don you've done it now, this will go straight to Denny's head & he'll believe that ..joe

Just a report on this situation after allowing some time to see if the "fix" works. It turns out that we decided the first thing to check would be to flush the transmission since that was not done for over 25,000 miles. To my amazement the folks who drained the trans said it was 3 quarts overfilled! They said the symptoms we had could be caused by too much fluid. I wondered why it would not overflow but apparently there is room for that much trans fluid to be sealed in without burping out. Anyway after the flush and adding in the correct amount of fluid the symptoms have not returned, although my son still does not completely trust the car. Even so I think this simple mistake was the main problem. Why didn't the extra level show up on the trans dip stick? I thought I did check it "hot" but ultimately I did add the extra on more than one occasion thinking the trans was leaking and probably the trans was not hot enough to give a correct reading on the dip stick, but I find it amazing that I could not see the extra three quarts on the dip stick!

Don Shillady
Retired Scientist/teen rodder