Did you check/clean your throttle body. How about the MAF sensor? Looks like you tried everything else!

 

cleaned the throttle body as well as relatable the throttle sweep. Maf sensor is good and reading what it should. So other than replacing the fuel pressure regulator in not sure what else I could be fighting...I don't believe it's a burnt valve or anything internal like that as it isn't smoking at all. So will be picking up a new fuel pressure regulator, replacing it and then going from there. Fingers crossed, because at this point I'm tired of chasing the gremlin.

 

Fuel pressure regulator is a possibility. No MAF sensor on a 2004 4.2L engine.

Check the EVAP purge solenoid. It is located on the driver's side of the engine block about midway back and midway down.

Are you able to monitor your fuel trims?

 

I can, however the long term got reset, and haven't run it long enough to get a value reading yet. When I look at all the evap stuff in my scan tool it's showing that everything is doing what it should, but I did get a code about possible fuel cap issue? I'll have to check it again. I'm changing the fuel pressure regulator, and I'm going to double check all of my fuel trims, as well as recheck everything in the line of evap, purge, and vent. The map sensor is what I meant to say not maf.

 

I would only change the fuel pressure regulator if it is leaking. Pull the vacuum line off of it and if gas runs out, it is bad. No gas, it's good.

Fuel trim values are not able to be reset.

Ideally, you want the sum of the Short Term Fuel Trim (STFT) value and the Long Term Fuel Trim (LTFT) value to be in the range of -10% to +10%, The STFT values will bounce all over the place while the LTFT values change much more slowly and tend to stay within a fairly narrow range.

 

well if the fuel pressure regulator isn't bad, then what would cause the strong fuel smell when there is no leak visible? Engine doesn't smoke whatsoever so I doubt it's an internal problem, however I'm somewhat new to the 4.2 trailblazers. I had a friend of mine tell me that it could be a bad fuse box. He said that he has had to change 4 or 5 fuse boxes in trailblazers that were throwing a P0300 random misfire code. Fuel pressure regulator is suppose to be here today, but I will check it before I replace it. I appreciate all the help chasing this gremlin down. Hopefully it is the fuel pressure regulator, but if it's not in not sure what direction I should go from there.

 

You want to look at the EVAP system. There is a fairly rigid black nylon hose that with a Green cap on it near the power brake booster The port with the green cap is the EVAP system test port where smoke is often injected in the system (around 1 - 2 psi) to aid in finding EVAP system leaks.

Also, there is the EVAP Vent system solenoid mounted to the engine block about halfway back to the firewall, and about halfway down. There will be black nylon tubing going into it, and a wire connector. If the solenoid is not closing, you can smell gas, if the tubing is cracked, you can smell gas. If the EVAP solenoid's case is cracked, you could smell gas. This is especially true if the EVAP charcoal canister is saturated with gasoline.

Additionally, if one of the O-rings in the fuel line connectors has deteriorated gas could leak there.

So, Diagnose, Diagnose, Diagnose, and then repair what is bad rather than blindly throwing money at the problem hoping you will stumble across the problem.

Good Luck!

 

evap smoke test was inconclusive. No leaks detected anywhere. No leaks in fuel lines, injectors, or anywhere. After replacing the pcm I no longer have any misfire codes, and previous po606 hard code is now gone as well. Still fighting rough idle. Not sure what else to look at. Plus are good, coils are good, fuel pressure is good, fuel trim long term says "0" so if it can't be reset then i don't know how it's on zero.

 

My 06 trailblazer is throwing a knock sensor code. Where is that located at ?

 

Carrie1986 - What engine is in your 2006 TrailBlazer?