Help! I need to diagnose a possible engine prob

[Chi Towns Haven]

I purchased a '94 Green ATX with 96K. When the car warms up (about 10-15 minutes after a cold start @ 40 degrees) the "Check Engine Light comes on". From there I either shut the car off or let it run until it goes off, which it does shortly. When I shut the car off and turn it back on the CEL light is off and comes on in about 10-15 mins. When I run it out, the CEL light comes on periodically. When the CEL light is on, I experience no probs whatsoever. The engine is fine. I ran a EEC self check and came back with error codes 172 and 173 which is rich and lean mixture. Does anybody have any ideas or similar experiences that will help me with this problem.

Another problem that may be related is that when I accelerate slowly, the throttle body makes a grainy, clearing-throat sound that is different from the regular sound. This may be related but I am not sure. Thanks for your help!

FYI: Meticulously maintained, new everything (tires, filters, brakes), no exaggeration (so i suspect 60K service, but don't know for sure). I have been told that it may be the o2 sensor or a dirty fuel injector. I put fuel system cleaner through it and it seemed like it happened not as frequent as before.

 

[Chi Towns Haven]

Forgot to mention: I have had it for 1 1/2 weeks. Bought it from a dealer. I have used only plus or premium fuel. The Fuel injector cleaner I used was Chevron Tekron (if that makes a difference). No mods except for a shift kit, it has EVERY option for the 94 year and it is in mint condition previously owned by one-owner, 60 year old.

 

[twr]

Bsd O2 sensors would be my first quess.
Terry

 

[sdpatt]

No need to guess. The EEC codes indicate the rear bank O2 sensor is not switching and has failed. This will hurt the fuel economy as the engine control processor is not able to enter into the "closed loop" mode to optimize the spark and fuel. The sensors are probably original and therefore due for replacement. They should be replaced with the spark plugs at 60,000 mile intervals. Pick up a couple of either Bosch P/N 13223 or P/N 15716 from AutoZone or AutoZone.com for $40.99. The sensors are located in the exhaust tubing just downstream of the ****** at the exhaust manifold.

The rear sensor on the your ATX is a little challenging to get to and definitely benefits from having an O2 sensor socket, universal joint and at least 9" of extensions on the socket wrench. The rear sensor's connector is best accessed while laying on top of the intake manifold and reaching an arm bewteen the engine and the firewall.

Welcome to the SHO.

 

[Chi Towns Haven]

Thanks for your help sdpatt. I went out to Autozone and bought a couple o2 sensors and installed them this afternoon. Car runs better than before and the check engine light doesn't illuminate.

Keep up your good work in helping naive SHOwners like me. thumbs_u