Ton of Engine codes... What to do?
 

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What could I do to attempt fixing my car? It is driving very slowly, the idle is kind of all over the place, and it just feels sluggish and not gas efficient. Do you think the computer is shot?

Thanks!

Based on your earlier thread describing how you installed the wrong size rear brake pads on your car I would say take it to someone who knows what they're doing.

Maybe it's never occurred to you but if you're involved in a serious injury accident and an investigator discovers you've personally botched your car's BRAKES, you will find that does not help your case at all.

Those darn CEL codes. OK, first off its rarely the computer at fault. If you read into the codes they are pointing to a basic root cause: The engine's fuel mixture is off. The fact that your O2 sensor threw a code is really saying the system can't compensate - so I'd go upstream to what controls the mixture and start checking stuff from simple to complex.
1. Study the vacuum diagram and see if there's anything obvious like a torn vacuum line. The vacuum lines actuate different controllers required in the fuel delivery system.
2. Mixture is controlled differently at idle vs open throttle so you need to do some investigations. The big three are a) MAF (the mass airflow sensor) which has a wire grid to measure airflow on intake. if dirty it will give false readings. First step is find the MAF (google some Youtube vids) and inspect/clean. b) the idle air control valve. Typically this can also get gummed up but I wouldn't expect it to mess up your open throttle performance - just the idle. c) fuel pressure regulator. This needs a pressure tester. Also note the MAF's little brother is the MAP sensor (manifold air pressure) which can also cause false readings (particularly if its vacuum line is broken) and throw codes. You didn't mention your model/year/engine so I can't say if you have an ETM (electronic throttle module) or not but on some Volvos, it can get gunked up or have a bad sensor that throws codes similar to the MAF.

So here's your homework - 1) inspect all the vacuum lines 2) research via google/youtube/forums the typical codes and symtoms for problems with the MAF, IAC, MAP, ETM and FPR. 3) set up a plan to inspect/clean the MAF, IAC, intake (use CRC MAF Cleaner, not generic carb cleaner on the MAF) 4) try some of the recommended test procedures (ie starting the car, disconnecting the MAF connector etc).

Hope this helps turn you into a DIY type :-) and just ignore those other contributors who suggest you buy a Toyota!!! (yeah I own one of those too...) We will get you over to the dark side of shade tree auto care.

First off we need to know what year the car is. If it a 2004.5+ there was a problem with the oil trap boxes that would make multiple codes come on during a cold start. If you think this is the case you can get the car hot and erase the codes. Then run the engine again and see if the codes come back, if they dont let the car sit overnight and then turn the car on and read the codes. If the codes come back then more than likely it is the oil trap box.