Questions and Answers
Backfiring Olds
Q. I have a 1987 Oldsmobile Delta 88 FE, 135,000 miles. Engine is a 3.8 litter, A/C. and auto transmission. It has power steering, power brakes, no ABS, cruise control and fuel injection.
Here's the problem... a while ago, my wife noticed some backfire which was very loud. The car was beginning to stall, then backfire, and sometimes would stall on turning corners. I replaced all spark plugs and wires with new ones. I replaced the muffler which looked like an old trash can after all the backfiring.
I have not fixed the problem as the car still 'quits' after certain use. Here's where it gets odd... we can drive the car anywhere from point A to point B, no problem. If I shut the car off, restart, and return to point A, the car may lurch once or twice, then lose all power, (stall). This always happens AFTER I've driven once, shut down, restarted and driven again... never happens on the initial first drive to wherever. The fuel pump was replaced last year, and the fuel filter has been changed within the last year. Fuel injectors were cleaned within the last year as well.
Any ideas?
A. This has to be one of the strangest set of symptoms I have seen in a while.Not the fact that it backfires, but it only does it on a return trip.
I don't know how much help I can be to you. I can give you some reasons for the backfire, but as to why is does it on return trips, I have to admit I'm at a loss to explain that part. Of all the cars made in the world, I leave it to GM to come up with the strangest problems.
The main reason a car backfires is because a valve is not closed when the spark plug fires. If it is an intake valve, it will backfire through the intake. If it is an exhaust valve, it will backfire through the tailpipe.
There can be several reasons for this. The valves are adjusted too tight. Valve stems can be slightly bent and not allowing free movement up and down. Or the ignition timing can be off. There can also be dirt and sludge buildup that is causing the valves to stick.
There can also be a problem with the emission control system. There is an anti-backfire valve that can cause the backfire if it is bad.
The loss of power would make me think that the problem is most likely in the valve train. I guess the first thing I would do is try cleaning the inside of the engine somewhat. To do this, drain the oil and remove the oil filter. Then refill it with oil, replacing one quart of oil with one quart of transmission fluid. Install a new filter and drive it for about 1,000 miles. Then do it again. If you notice an improvement, then you know it's getting clean and things are moving the way they're supposed to again. If not, then you have a mechanical problem.
I hope this helps you, please, let me know how you make out.
