1991 calais backfire through carb...

[thomas_covenant]

Howdy!
1991 Cutlass Calais. 2.5L carb. Automatic tranny. 217K miles. Purchased a couple months ago. Last week started backfiring through carb when accelerating hard or (PUM! then hesitates, sometimes stalls). Always starts great. Never a problem with starting. It runs great other than this problem. I drive it to work every day (no freeway, speeds up to 45). I have also noticed that if it's accelerating in D it seems to do it more than in 2nd when at lower speeds.
The SERVICE ENGINE light is not on. There are no codes in the computer.
I disconnected the O2 sensor and it made no difference.
Any help very appreciated, as I know basics about carbs and lots about FI, but nothing about these electronic carbs with O2 sensors.
Thomas

[GTP Dad]

Do a compression test on the engine. This sounds like a burnt valve in the engine. The other possibility is a bad camshaft.

[jsgold]

Wouldn't he have a TBI injection, not a carb, on this engine?? If the other stuff checks out might look it over and maybe throw a rebuild kit in it if nothing else turns up. My dad's 89 Olds had 176K on it and we noticed the TBI was leaking around the injector and back area when we did the head replacement. Rebuid is pretty easy if it is the same type...

[maxwedge]

Originally Posted by jsgold

Wouldn't he have a TBI injection, not a carb, on this engine?? If the other stuff checks out might look it over and maybe throw a rebuild kit in it if nothing else turns up. My dad's 89 Olds had 176K on it and we noticed the TBI was leaking around the injector and back area when we did the head replacement. Rebuid is pretty easy if it is the same type...

Good catch, has tbi, also could be just a crossed plug wires.

[thomas_covenant]

Originally Posted by jsgold

Wouldn't he have a TBI injection, not a carb, on this engine?? If the other stuff checks out might look it over and maybe throw a rebuild kit in it if nothing else turns up. My dad's 89 Olds had 176K on it and we noticed the TBI was leaking around the injector and back area when we did the head replacement. Rebuid is pretty easy if it is the same type...

Right you are! In another post I mentioned that I had discovered this. It is a TBI.
Thomas

[thomas_covenant]

Originally Posted by maxwedge

Good catch, has tbi, also could be just a crossed plug wires.

Thanks for the advice...I actually forgot to mention that I had sprayed mist onto the wires and saw nothing...but that the first thing I was going to do was plugs and wires.
I finally got the parts and installed them and discovered a cracked plug on #2 cylinder. Guess the previous owner must've dropped one or something. It runs beautifully again!
Thanks to all for suggestions!
Thomas