Running extremely rough

[dpas]

My 1991 with 273,000 miles started running extremely rough. The odd thing about this is it ran great coming home from work. I parked it in the driveway and then went to run an errand an hour later and the engine would barely run.

At 262,000 the engine was running a bit rough (nothing like it is now) and the mechanic indicated that there was a misfire on cylinders 3, 5 and 6. Fuel injectors were cleaned and new plugs solved the problem.

At 267,000 miles the engine started running rough again and there were misfires on cylinders 5 and 6 and one fuel injector wire was apparently shorting out. Spark plugs were replaced and short was fixed solving the problem.

So I'm only getting about 5000 miles between fouling out plugs.

I am going to pull and look at the plugs myself over the weekend. Not sure this is the cause as the roughness is extreme and it happened so randomly but that is where I will start my diagnosis. I have had this vehicle since new. It has been babied and had full synthetic oil changes since day one. Heads were replaced at 226,000 miles. Is there anything else I should look for? Why would the plugs be fouling so frequently?

Thanks!

 

[trashtruck]

might be plug wires or even losing the coil pack.

 

[vq5speed]

Will stay idling if you let off the gas

 

[dpas]

Pulled 5 of the six plugs (had trouble getting to number #3 by the heater box) Number five looked black like it has not been fireing normally. All others had a normal looking tan color. Tested for spark at the five plugs that were removed and they appeared to have good spark.
The car idles extremely rough. Once you get going up to about 30MPH things seem to smooth out and you don't notice the bad missing at that point. I believe it is still missing but just not noticeable.

My next guess is something going on with fuel injectors. I have never tested or repaired fuel injectors before so I will start studying the forum.

Thank you for any thoughts and suggestions.

 

[dpas]

This engine is toast. My mechanic just called and gave me the news that cylinder #5 has zero compression and is full of oil. Not sure what happened--as i have owned and babied this vehicle since new. Time to start looking for a new ride. I would like to find another 1st generation if possible.