Well. Couple things. Running into some issues and would just like some insight possibly.

1.) having an issue while the truck is running. Mostly when idling. I’m lost my sync signal between the cam and the crank Again.... I fixed this problem with a new pcm. And yes I know 100% sure my old pcm was the issue. Months later, it does it again. But I also know that’s not what’s causing my problem now. But maybe this will have something to do with number 2

2.) Key on engine off, everything works, then all of a sudden I get random spasms. Like I’m turning the key on and off so quick. It will click all the relays, fuel pump, the whole 9 like I’m turning the key. But will do it faster than I can actually turn the key. Bad ignition switch? Losing power for just a quick second then coming back to life? I have a video I can post if somebody recommends I do.

3.) I have a P0171. LT fuel trim is maxed at 32. Give it gas and goes back to 0- then slowly will get to maybe 4ish. That says vaccuum leak. I’ve searched for this vaccuum leak by using the infamous brake clean and also a spray bottle of water. Can’t seem to find it. Not the 02. Just replaced. Plus the readings on the live data look good with the 02’s. Not the plenum gasket. Just did that not even a year ago actually. But looked down in the TB for the heck of it and looks pretty clean. Doesn’t look bad. Can’t seem to find it on the engine. Looked at vaccuum hoses but they are so small and even the slightest crack wouldn’t cause it to lean out so much. But I still checked and hoses are ok. Some had cracks but replaced those. Can’t seem to figure it out. It’s driving me nuts. Any ideas?

 

Disconnect the front O2 sensor. See if it runs any better.

How old/what brand cam and crank sensors?

 

If it does run better what are you suggesting? I don’t think it will but I can give it a whirl. And I’ve used both stock and aftermarket crank sensors. Does the same thing.

 

I would check voltages at the pcm coming from the key switch to see if that is the issue. How are the grounds? Might try wiggling the wires going in to the pcm.

 

I’ll go ahead and give that a look tomorrow. I know one ground snapped the other day. One that went from the firewall to the back of the head I believe. I intend to fix it tomorrow. But don’t fully believe that may be my issue

 

Update - Did a lot of work to it today. Had some vaccuum line issues for the 4WD and AC. Fixed it. Replace crank sensor. Fixed that problem. Ignition problem seems to be okay for now. Still got the lean issue though. My LT fuel trim comes up to +32. I can smell the fuel in the exhaust. It’s definitely running rich. But on the scan tool the upstream 02 looks like it’s doing its job. It’s switching from lean to center 66% of the time and 33% lean to rich. (I have a graph.) using a snap on Solus pro. I have a lot of data to read. Just not really seeing anything out of the ordinary. Give it gas LT goes to 0 but starts rising again. I felt like vaccuum leak but I’ve gone through so much today it I’m not seeing any vaccuum leaks. Any suggestions? Maxing out at +32 worries me. Plus I’m going through gas like crazy

 

What does the PCM think Engine temp is?

If the O2 is switching properly, but you are still running excessively rich, I would suspect a bad sensor.....

 

very good thought. And I’ve thought about that as well but never seem to spark my attention. 160 degrees would be cooler obviously. But cool enough to set my LT to 32?

 

Hhhmmm..... that implies the PCM thinks the engine is running lean, so, it adds fuel. Why the O2 sensor would be lying is an extremely good question.

Might not be a bad idea to verify sensor input voltages. If voltage is wrong, the readings will be as well.

 

well I have replaced the sensor now twice. When I changed it the second time it was because I thought what you did. O2 sensor may be faulty. But don’t think it is. Same result. Do these also have a 5v reference? I can see the 02 sensor voltage on scan tool as well. Which are you talking about? The voltage going into the sensor from the harness or the voltage readings on the scan tool?