Every now and then my car will throw codes 33 and 34, and run rough. I'm thinking the MAF is probably on it's way out, but is there anything else to check before I replace it?

Also, the car failed emissions, for nox too high. The EGR, catalytic converter, O2 sensor, and CTS are only about a year old. Could it be possible a failing MAF is causing high nox?

 

Replace the MAF power and burn relays first. While your at it check the wiring on the relay plugs, over time the insulation slides down exposing the bare wire this could cause problems as well.

 

If its intermittent i would definitely start by checking out your wiring. As far as NOX is concerned yea a bad MAF could cause the car to run lean which would result in high NOX however then again alot of other more likely things could cause high NOX. I would check over the EGR system, AIR system, Ignition timing, check the plug color to see if your running lean.

 

I'm going try troubleshooting the EGR system tomorrow. The EGR valve only has about 10k miles on it, but the solenoid hasn't been replaced. Also, I am going to try replacing the MAF power and burnoff relays before spending $150 on a new MAF.

About the relays though, are they the same as the fuel pump relay? Autozone couldn't find any part number for them, and O'Reillys only had a general GM relay. I bought 2 of them, but I want to make sure they will work before I plug them in and short something out. They are the normal GM 5-pin oval type, Master Pro PN R4005.

 

the oval relays are all the same, if they can't find anything under maf sensor ask for cooling fan relays.

Older third gens have square relays that are 2 different part numbers, but I'm not sure when the change-over was.

 

Well, I did some troubleshooting on the car today. There are 3 relays next to the brake booster - the one closest to the booster is the square type, and the 2 others are the oval type. I replaced one of the oval ones with a relay I had bought, but the other one wouldn't fit - the one closest to the fender. It only has 4 wires, so that would have to be the MAF burnoff relay right? Anyone know for sure which relay is which?

Also, I bought a vacuum gauge and checked the EGR, it does not hold vacuum at all. Its a negative type, it does have an "N" stamped on it, so I'm assuming it's bad. I also found that the EGR solenoid connector was broken, and possibly not making a good connection, so I'm replacing that connector. I also found that the canister purge valve was not holding vacuum, and since it shares the same vacuum line as the EGR solenoid, I'm replacing that as well. Hopefully these issues are the cause of my high NOX.

Once I get it all back together I'm going to tee into the EGR vacuum with the gauge and see if it's working or not, but when does the ECM actually open the EGR valve?