Hi all, Just picked up a '97 Silverado K1500 with the 350 vortec and 4spd auto. It's throwing the p0172 and p0175 codes.(too rich on banks 1 and 2) How do I determine whether it's the MAF sensor, MAP sensor, or o2 sensors? My freeze frame data is as follows:

Abslt TPS = 22.4%
RPM = 1715
Calc. Load = 21.6%
MAF LB/M = 5.82
MAP Hg = 19.8
Coolant = 198F
LT Fuel Trim 1 = -14.8%
ST Fuel Trim 1 = 0.0%
LT Fuel Trim 2 = -18.0%
ST Fuel Trim 2 = -3.1%
Speed = 32
Fuel System 1 = Closed
Fuel System 2 = Closed

With the truck off and cold this morning, my MAP Hg was 29.8 (correct for our altitude, about 400 ft. above sea level) Does driving and load affect that? Also, the MAF LB/M was 0.33. With the truck off, shouldn't this read zero? The coolant temp and IAT were both accurate at 43F degrees, so the thermostat isn't sticking and the temp sensor is ok. Any ideas? I don't notice any hesitation or bog (which there should be if the computer is enleaning it, correct?) I did notice it sounded a bit like a diesel from a cold takeoff last night, though (that's the best i can describe it). Thanks for any help!

 

Since your not getting any running conditions.. i would try cleaning maf.
Clear codes and see . Do not think 02 they are working picked up the rich conditions.
Check that all is tight down stream of maf. Any un metered air will cause probs.
Even a dirty air filter.

 

I concur on the MAF cleaning. It's not likely the O2 sensors are bad on both banks. I don't see anything on the MAP reading which is mostly affected by the throttle opening. There's obviously too much fuel for the given metered air. Any aftermarket calibration/modification for a CAI, non-factory MAF and injectors, even if not there now?

 

Thanks guys, that's the concensus I've been getting. I'll try cleaning it out and clearing codes. I didn't think both o2s would go. I've read that if you clean the MAF its probably time to replace? Should i voltage check and see how that works? Also, the light went off today while I was driving around does that mean anything? Thanks again!!

 

Just run it .. if code comes back check maf out. If it was out of specs would surge
Have hesitations ect.

 

The MAF sensor isn't cheap and thus it's not something to be replaced lightly. The malfunction indicator went out because the long term fuel trim values improved to the acceptable range. It wouldn't hurt to spray down the MAF sensor with the appropriate cleaner, though.

 

Any ideas what the "diesel" sound might be?

 

Earlier I posted about the piston slap in thread https://chevroletforum.com/forum/sho...638#post175638. I think it sounds worse than what it is.

 

That sounds bad... It goes away after temP rises, I'll have to check oil press. next time

 

My 'check engine' light was on. They changed one catalytic converter and the light went out. It's on again. Anyone know the codes for this problem?