CamaroSS1999

I recently bought a 99 SS w/50000m on the motor. There have been no aftermarket mods done. The only thing I've done to this car has been an intake clean, which proved to be a bit of carbon buildup and it seemed to run okay. But now I have some stumbling issues with the car. It runs rough at about the time it gets ready to shift, and at idle. It's not throwing any misfire codes just the p0137 and 0157. My roomate is a master certified ase mech, so we hooked it up to his computer, (and not one of those 150.00 computers from autozone) it was a snap on computer which gave readouts. Bank 1 sensor 2 was reading nothing so I assume it was going into open loop mode. Prob is I changed the sensor and I am still getting the same codes. I don't think the after cat o2's should cause any performance issues, and since I changed one to a oem bosch i figured it would at the least take care of one of the ses codes it was throwing - NOPE. Still having stumbling issues. I did find out the previous owner let the car sit for a year (said he started it each week) and he put 87 octane in it the entire time which was maybe 5000 miles. Well I tried 91 and octane boost to try and clean out the system and still getting the stumbling code. I pulled the a plug and there are plat NGK's allready in there gapped at .60 and they didn't look too awful. But what would still cause those codes to come and my car to stumble? I'm at a loss cause I just want to keep this car stock and running good - I have other plans for an older 94 z to fix for racing so I'm keeping my gem for the garage. I just want it to run right. I also replaced the air filter to a standard penzoil we had up at quik lube, but I'm going to install a k&n as soon as i get paid on thursday. I wouldn't think that would cause problems either. Maybe the codes and the stumbling are two unreleated issues - i'd have to assume so since the after cat o2's shouldn't affect performance. But no other codes present themselves except a p0650 i think... anyways, it's because my dash cluster wen't capoot in rainy weather - it comes on and goes off every once in a while. It wasn't like that when I bought the car it just started a few weeks ago and a dealership confirmed it was the cluster itself - which I hope is unrelated itself. I don't think it's the cats either as it only has 50000 miles on the car and it runs really well at wide open throttle. Help plz as i've done this for many years and love f bodies, but sometimes they get under my skin.

Thx a bunch,\

Shannon.

99345hp

what did your friend the mechanic say was wrong with it? If he was with the car and had a scan tool and other diagnostic tools with him, then why didn't he diagnose the problem for you? what readings are you getting from your after cat O2 sensors? They should be reading at or around a steady half a volt. That wont cause any runability issues, but will cause the codes to keep coming back.

As far as the stumbling issue. That could be many different things. Plugs, vacuum leak, fuel filter, injectors, maf issue, etc. Something like that is a lot easier to diagnose while you are right there with the car.

406malibu

Use a few of those, and I'll read what you wrote and maybe be able to give a suggestion or two.

CamaroSS1999

Okay, well I ran techron fuel system cleaner (about 7 bucks at wal-mart) right through the fuel rail and it fixed the stumbling issue. No codes are popping up now. I think with the intake clean it eliminated a majority of the buildup and with an open injector setup it was causing the system to run to rich. Now it is just right - it feels like a brand new car. I didnt check the post prior to performing the injector cleaner, but it seemed to be the next logical step as the previous owner ran only 87 octane in the fuel system for nearly 5000 miles and didn't drive it much at all. Thx for the info though.