So after buying this truck and getting the shaft, I have incurred the problem of chasing a gremlin. The truck did fine for a few days but then I have been getting a p0171 and p0174 code, and it started idling rough soon thereafter. I cleared the code but within a hour it came back on. I can drive the truck a few miles and then everything is fine except the SES light is on. Supposedly it has a new MAF and new o2 sensors..... I am thinking its in the tune, or it need a intake gasket job....but not really sure where to start.

Any suggestions?

 

I would start with the cheap and easy stuff, spray some MAF and TB cleaner, change the plugs (I like TR55 gapped at .055"), change the fuel filter, give it a good seafoam top end treatment. If it doesn't fix the problem, then it was good to do anyways. I would check the front O2 sensors; if he replaced them, he might have cheaped out and gone with some Chinese brand instead of OEM Delcos.

 

If you can find someone with a good scanner check the misfires on your cylinders. As my Escalade reached 100K I noticed it was running rough, etc and put the scanner on it, LTFT had increased. Scanner showed No.1 plug wire-looked good in the truck-was misfiring. Put on all new plug wires and all is good.

 

plugs and wires were replaced 10k miles ago. I will try to get efi to log the ltft and voltage of the o2's.

 

I had a p0174 and p0300. I replaced plugs, wires, intake manifold gaskets, 02 sensors, and cleaned out the maf. I ended up running some sea foam through it and ran it at high rpm and my driver side cat exploded and fixed everything haha. Anyway, you could test for vacuum leaks by spraying starting fluid around the intake manifold. That doesn't work check out your cats.

 

There are small box like shapes by where the intake runners mate to the heads on cyl 1 and 8. Spray some fuel injection cleaner in these to see if you have bad intake gaskets.

 

Intake manifold gaskets... Or some kind of vacuum leak.

 

started pulling it apart last night to check it out, it had a cracked k&n tube on the intake right at the TB. put a new one on and its fixed! On to the next thing...... not sure but the previous owner had chased this lean issue although I wasn't told about it until on my way home the light came on. So its now fixed and that should take care of all of the problems that arose with the truck. Thanks for the input guys, what I experienced was exactly what you all thought, Intake leak...... just not at the manifold