Please Help!

secretgoldphish · July 30, 2011

Sorry to bother everyone but after doing some searching online I have been unable to find anyone with my exact problem who has come up with a viable solution. I have an '03 Silverado 1/2 Ton 4x4 with the 5.3L engine. The problem I have occurs intermittently and doesn't seem to be affected by temperature. In park the truck will not go over 1500 rpms, the motor more or less stops there, it doesn't really miss or backfire it just sort of stops. If I am driving it down the road and it occurs you can feather the gas pedal and it will accelerate slowly but if you push the gas to the floor the same thing happens the rpms fall and it has no power. It has spit out the following codes: PO171- System too lean bank #1, PO174 System too lean bank# 2, PO131 O2 Sensor circut low voltage bank 1 sensor 1. PO151 O2 sensor circut low voltage bank 2 sensor 1. When I clear the codes out I can take it down the road and it the problem will occur without tripping any codes at all, it seems to take awhile for the codes to reappear. I ruled out the O2 sensors as it occurs occasionally on cold start up and I think the ecu runs on a closed loop circut prior to the Sensors getting to temperature and the ecu taking into account what they have to say via an open loop. From what I understand the intake manifolds are known for leaking on these trucks but I'm hesitant change out the gaskets or potentially the manifold if it is warped without being relatively certain thats the problem. I also thought perhaps the fuel pump was going bad, I don't have a fuel pressure tester and I wanted to avoid the cost of taking it into a shop if possible. I was hoping someone might have run across a similar problem and would be able to help me out. Thanks in advance so much for any help, ~Mark

wavery · July 30, 2011

Have you tried replacing the fuel filter and air filter? I think, I'd start there.

Could be a bad TPS but the codes don't make sense. Could be MAF sensor....... or a hundred other things.

Spraying WD40 around the intake would tell you if you have a vacuum leak.

I'm sure that someone will pop in soon that knows the codes far better than I do.

I know that I wouldn't drive it until I got it fixed....... that's for sure.

secretgoldphish · July 31, 2011

Wavery, Thanks for the quick reply. The air and fuel filters both have less than 5k miles so I didn't think the problem could be there. I did spray some light oil around the intake with no discernible difference in the engine idle/performance but from what I was reading it can be difficult to detect a leak on these particular intakes. I checked the TPS with a multimeter and it appears to be working properly. The MAF is certainly a possiblity although I would think it would kick out a code pertaining to the MAF i.e. PO101 if this were the issue. I certainly won't be driving it until I get this resolved, thank you so much for your input. ~Mark