95 Lumina APV problems, suggestions wanted

First of all, I have sound this forum to be a great source of information, and decided to join today. This seems to be a great place.

Our teenager recently purchased this vehicle, and has run great up until recently.

Here is the problem:

1995 Chev Lumina APV, abt. 115k miles.

The kid reported a month ago that the vehicle started to backfire, then it went away for 2 weeks.

Then the problem returned again, and has remained since.

Here are the symptoms:

Backfiring through the exhaust, when you let off of the throttle.

Backfiring through the carb too, inside of the air filter is wet.

Will not accelerate unless you give it a lot of throttle.

When I listened to the motor, there was a fairly loud and constant air hissing noise near the area of the carb (throttle body). There were several vacuum leaks, and I think that those are fixed, but the hiss is still there.

There was a point where there was no power at all, and he had to have the car towed home. And yet now it runs (poorly), and he drives it a short distance to work every day.

Ofcourse, teenagers are not quick to fix these sorts of problems, and he has been still running it in this condition. And I suspect that more problems are happening because of this.

The backfiring caused the catalytic converter to split, and he replaced it with a strait pipe.

He has had the electrical system tested by Midas, and Auto-one, he was told there are no bad sensors. But he was told that 2 spark plugs on the rear bank are fouled, and the 3rd plug is "almost fouled". The technician said that the exhaust valves are stuck, (I think that is BS).

There is no antifreeze in the crankcase oil, and no oil in the anti-freeze. And there was no white exhaust either.

I am at a loss as to what the origional problem was. (Help!)

But I suspect that the backfiring may have blown a head or intake gasket. Or perhaps one of these gaskets is the initial cause of this.

Any suggestions or thoughts would be of great help.

Clean you intake. Go buy a can of Air Intake/throttle body Cleaner for a couple bucks and replace the spark plugs.

take the throttle body off, and clean it out with some carb cleaner, or something along those lines. Put it back on. You'ld be surprized what this can do. Also, it sounds to me like its running real rich, maybe O2 sensor. Hey, you never know. I'm leaning more towards a timing issue. I'm not sure if these apv's have belts or chains, but it the timing is retarded just a little, I believe, (correct me if I'm wrong), that the engine will still run, but run real rich. Could also be a (or a few) leaky injectors. I dont know what else to tell you. Good luck with it. Keep us informed.

Boy, thanks for the replies. Frankly, I am a PC hardware guru, and a mechanical engineer by trade. But I know my limits, and where to ask for help.

I know this is a auto forum, but I am always available for PC hardware and some software support.

The replies have not gone unheard, and will pursue it.

Thank you.

good luck. Keep us informed