Cadillac Allante Forum Discussion, 1988 Slight backfire under acceleration in Past Cadillac Vehicle Discussion; As I mentioned in a previous post, just purchased a 1988 Allante. Car is in great shape, starts easy, runs ...
As I mentioned in a previous post, just purchased a 1988 Allante. Car is in great shape, starts easy, runs great...with one exception...there is a slight backfire (pop) under acceleration. Sounds like just one cylinder missing sometimes. I do not know the history on this car. Is this a common problem and is there something I should look at first?
Pop from under hood or from the tail pipe? From the tail pipe I would suspect plug wires. Are we talking about quick acceleration? A series of pops?
Its from the tail pipe. It does it even under "moderate" acceleration, you have to be very gentle to not have it pop. It is a series of pops but separated by time such that I think its only one cylinder. You think its the plug wires? I was kind of thinking maybe a fuel injector that wasn't closing all the way or maybe a sticking valve. Plug wires would be easy to start with.
Yeah, a "backfire" from the tailpipe is called a "muffler report". It's caused by fuel vapor in the exhaust. Either too much fuel is being injected (faulty FPR, stuck injector...), or there's a misfire.
Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
Re: 1988 Slight backfire under acceleration
I used the Delco plugs designed for a 91 4.5 Eldo. platinum so they go 90,000 miles. When I did mine, I removed the 2 front sub frame bolts and lowered the engine slightly with a floor jack to gain more rear access. Plan on wires, They will be stuck on the plugs!
Fuel pressure regulator is rather uncommon to fail on this engine. With the service manual instructions, you can short out each cylinder thru on board diagnostics to isolate which cyl is acting up.