Help!! 92 Buick Lesabre Engine Is Running Rough

Bought used.The car is running really rough. It hasn't died in traffic yet but I know its coming. Fuel to engine acceleration sputters. Plugs and wires are good, fuel filter has been changed. There are no vacuum leaks. I haven't been able to find the pcv. Also, something to mention is when I removed the oil filler cap the car started to run even worse. Individual sensor plug removals revealed nothing worth mentioning. Computer error code was 58. I don't know if thats the passive fuel system or the tranny high temp sensor. If any one has any idea whats going on here, please feel free to comment. Question? Where are the tranny sensor, egr valve and the pcv? Could the catylitc converter be on its way to being clogged? Thanks!!!

Interesting symptoms - almost identical to what I had - bad idle, but ok acceleration. I think you should concentrate on what that problem code 58 is. I believe it is causing your problem.

In my case, I had purposely disconnected the low speed radiator fan relay (my fan was running contiinuously). The computer apparently didn't like this. It saw some sort of fault when it tried to turn on the fan, set and reset the check engine light at ten minute intervals, and my car wouldn't idle proper. The computer was in some sort of error retry mode loop. Reconnected the relay and everything immediately reset back to normal.

Has the oxygen sensor (before the catylitic converter) been changed? Is it kicking out any black smoke like the fuel mixture is not right? The 02 sensor is supposed to be changed at so many miles. If it has a lot of miles on it, that might be the problem. I would tend to focus on the plugs, but if they are new, maybe the ) O2 sensor.

i checked my chiltons manual and code 58 is something like pass-key fuel. perhaps your key is not an origional? do you have any other keys you could try?

Also, something to mention is when I removed the oil filler cap the car started to run even worse.

That is pretty normal - and indicates that your PCV system is probably working OK. What I think happens is that the PCV system keeps a very slight vacuum in the crank case and keeps the air circulating through it, and when you take the oil filler cap off, more airflow than normal can occur, leaning the mixture out a little (since the MAF sensor doesn't see that additional airflow). On my engine, the slight drop in RPM is temporary - I assume the engine computer adjusts for the situation...

Could the catylitc converter be on its way to being clogged?

Do you have access to a vacuum gauge? There is a test you can do to check for a plugged exhaust system (any basic Haynes manual or whatnot has the procedure).

The 02 sensor...

One way to identify O2 sensor related stuff - the O2 sensor is totally out of the loop at initial cold startup, so if it runs fine when initially started, and then a minute or so later it starts running badly, it could very well be an O2 sensor issue or other poor mixture control issue. But a bad O2 sensor "shouldn't" make it run badly first thing in the morning when you start it - just seconds to minutes later (depending on whether it is a heated sensor or not).