Dead plug???
 

Ok I finally got a problem that I think the collective brain power on here can help me out with. I have my own assumptions as far as to what might be wrong with the car but I would like to hear what you guys have to say. Last night I started up the vette and let it idle to get warm for a few minutes as I was talking with some friends. It sat idiling for about 5 min and then took on a lower sound almost like one of the cylinders stopped firing. At that point I decided I had better get in the car and go seeing as I was about 15 miles from home when I got in the car the engine became choppy and rough and i didn't feel like I was getting 100% of the power. As the motor warmed up a bit the car began to back fire at the lower rpm's. I figured I was only getting power out of 6 or 7 cylinders which might indicate a bad spark/plug but do you guys think it might be a carb problem or should I just buy some new plugs and find the bad one in the batch? Also the backfire was comming from the drivers side.
Let me know what you guys think.

RE: Dead plug???
 

Backfiring is usually a timing issue, and backfiring when the engine is hot/cold is usually a timing advance problem. Check the vacuum at the distributor, and the other goodies in the timing advance system, as well as checking your base timing settings. While you are in there, it is always a good idea to do a good tune up and check your plugs as well.

bill.

RE: Dead plug???
 

Thanks for the suggestion. My only question is the circumstance in which it happened. It was sitting there just fine then all of a sudden bam loss of power and very rough idle. Do you think a timing problem would just pop up like that?

RE: Dead plug???
 

Timing changes with engine temperature and revs... You might have been marginal but running OK until it warmed up, and then the timing changed with the temp and put you over the edge into "running crappy". I don't have my manuals handy, but I know there is a section on it in the GM shop manual.

bill.

(yeah, my wife made me go out and get a real job)

RE: Dead plug???
 

Check plugs (cracked insulator outside or inside), plug wires, vacuum at idle, dist. cap (carbon tracking can cause cross firing or moisture).

RE: Dead plug???
 

The symptoms your describing sound like an ignition issue, for it to go from smooth to rough that quickly sounds like a burned plug wire, dist. cap terminal, spark plug, or rotor. A slight possibility may be a lean missfire due to a carb problem such as debris plugging a jet or idle passage. If spark and fuel check out OK then start looking at compression problems ( valves, lifters, pushrods, cam)

RE: Dead plug???
 

I had a similiar problem on my ride home after buying my 79. halfway home she started to miss and sputter, dont really remember her backfire though. it ended up being a sparkplug wiretouching the header. i would start with a good tuneup if she hasnt had one in a while.