Ok, MPG is down to about 7. Had pending codes (SES LIGHT NOT ON) p0327 , p0134, p0135. So I cleaned the upstream O2 connections with the appropriate connector cleaner, let dry and reconnected. Checked for vac leaks and found a loose purge valve connection at the manifold and corrected it. Let truck sit for a while and fired it up, drove until warm and SES LIGHT COMES ON with codes p0327 ( I know what this one is) p0130 and p0150. I cleaned the MAF with the appropriate MAF cleaner and reinstalled. Drove until warm and NO SES LIGHT but still pending codes p0327, p0130 and p0150.

Both upstream O2's are BOSCH and less than 2 years old. The drivers side had a little gunk in the outside of the connector, passenger side relatively clean. Inside of both connectors very clean before and after cleaning. I have not changed the MAF in my 7 years of ownership. It was difficult to see how contaminated the MAF was before cleaning because of its position in the housing.

So after all that, the initial codes (p0327, p0134, p0135) after the cleaning of the O2's, MAF and the vac leak fixed? I am I understanding these codes correctly when they happen at the same time that it is something upstream of the 02's and not the 02's themselves?

Thanks

 

I've had every problem imaginable including multiple tussles with MAFs and the only times I got a 327 were when the knock sensor wire was touching the exhaust manifold and when something unknown happened to a knock sensor and I had to replace it (I still don't know what happened to it... It looked fine). But those combination of codes could point to the 02 from sensors both because the latter codes indicate them and because the knock sensor can go nuts when the engine knocks from a rich or lean condition that malfunctioning 02 sensors would cause. Have you checked on a scanner to see if the fuel system is open or closed?

Still, I've gotten immediate results from replacing an MAF even though the MAF didn't throw any codes. This week I was assembling my engine and got an MAF code for the first time in 16 years and I'd forgotten to connect it. That made me think that next time I had mystery codes I was going to unplug it and see if it made any difference in engine operation. If the engine operation did not change with the MAF unplugged then the MAF was the likely culprit. You might try that. Based on my limited observation, no MAF was no worse than a malfunctioning MAF.

Fwiw I've been using the cheapest amazon MAF you can get (about 35 dollars shipped) for 2 years with no issues. And at that price I always have a spare too.

At 7mpg when you fix this issue it will seem like you have a new engine!

Also, though you probably know this, the MAF gets VERY hot and has to sit for several hours before you clean it or the glass on the element will crack the moment the spray hits it.

 

Frank, the two O2 codes are both for Bank 1 so try swapping the upstream sensors side to side and see if the codes follow.

I have no experience with the knock sensor code, but I don't see why any of these codes indicate a problem with the MAF.

Diagnose, diagnose, diagnose.

 

Great info. I'll try the MAF disconnect to eliminate it as the culprit.

Thanks again.

 

Thanks for the reply. So the P0130 and P0150 are drivers side (bank 1 ) O2 codes? Or are you talking about the P0134, P0135? The p0134, p0135 are no longer showing up, pending or otherwise.

 

From the RAVE
P0130 O2 sensor circuit malfunction (bank 1, sensor 1) Front sensor LH bank stoichiometric ratio outside operating band
P0150 O2 sensor circuit malfunction (bank 2, sensor 1) Front sensor RH bank stoichiometric ratio outside operating band

Both codes indicate a problem with BOTH front O2's.

 

I guess I didn't read the whole thread carefully enough. Sorry. I was referring to 134 and 135.

 

I can't remember if I said before and this mobile app gives me a stroke, but be sure to check your o2 wires. I once had one flat on the exhaust and it caused all kinds of mischief. But I did find that by following the burning smell.

 

Will do. Thanks again.