I have a 2001 Blazer 4.3L 4WD. Either warmed up or cold the abslt % TPS for me Actron OBDII scanner reads out 0% at idle. It does move when I hit the accelerator. Is this value normal? I am guessing it is used to calculate load in some way. Can this cause my lean codes?

I have been dealing with intermitent P0171 and P0174 codes for some time and LTFT for Bank 1 and Bank2 are showing a lean condition and are dumping in a lot of fuel. I have snooped for any vacuum leaks with a fogger and no smoking gun found there.

Any help would be appreciated

 

at idle should be around .4-.5 wot 4.85, when i had these codes it turned out to be my spider injector assy so i put the updated unit in and it fixed those codes. do a fuel pressure test, leak down test and if it drops more than 5psi in ten you either have a leaking fuel pump or a leaking syder injection system. so you gotta take the fuel filter off and rig up a fitting to the fuel line and test pressure there again and see if that leaks down and if it doesnt than the problem is in the spider injector. so pull the upper intake off and inspect. in the diy section there is a thread on fuel system diagnoses.

 

Thanks war00,
I put in a new AC Delco fuel pump last summer. I was leaning toward a new spider but did not want to sink 200+ $ in if it was not the issue. I have 60 psi pressure at the rail and does not leak down. Also installed a new pressure regulator last summer under plenum with full gasket set.

 

0% TPS at idle is exactly what it should be. It means the TPS is closed all the way. It should smoothly rise to 100% at wide open throttle. As war00 mentioned, voltage should be ~ .4VDC and smoothly rise to ~5VDC at wide open throttle. The P0174 & P0171 indicating both oxygen sensors are reporting a lean condition to the PCM. It could very well be the oxygen sensors are reacting too slowly, commonly called a "lazy" sensor. If the sensors have 100K miles or more, they need to be replaced.

 

been on vacation. Thanks for they reply. Changed both pre cat O2 sensors with AC Delcos around 10k miles ago. I tried a new MAF today which appears to be the usual suspect with no change. I fogged the engine vacuum system and had leaks at 2 spots (out of the throttle shaft on the spring side but pretty small) (out of the front of the engine down below AC compressor - fairly large). This does not appear to be comming from the intake manifold. It appears further down well below the AC compressor.

Read a post earlier from swartlk that talked about a leaking AIR system that can cause lean codes. Not sure if I fogged in the correct line, I used the one that goes to the vacuum block for interior controls in front of the check valve. However there was quite a bit of smoke comming out down low.

 

Have another set of eyes watching when you fog it to see where it's coming from. You can fog between the check valve and the engine, or in the power brake booster line, which may give better results.

 

fogged again today with and without the PVC and breather lines plugged. Most fog seems to be coming out from what appears to be the timing chain cover. I confirmed this with soapy water. Since this post was on a TPS sensor I will start a new post.