PCM...

[Chuck Leeper]

Seems we have a "problem child" in our shop.
5.3/2004 Tahoe engine, and the complete driveline, ALL the harness, das, etc..The entire dash is even transplanted.
Engine starts, runs well, until it hits closed loop. About 80-130 frames, [EFILIVE data logging], After closed loop comes on, the STFT goes straightline to -33%, and the O2's go to straightline .995+/-
ALL other sensor inputs are normal.
This is a complete 30K drivetrain pullout, transplant. The engine is bone stock.
We've tried: 2 ecms, countless tune changes...The results are exactly the same.
2 other shops, ours, and various others w/ suggestions = No answers.

NE1 want to venture a guess?

 

[TurboBob]

o2 sensors swapped left-to-right?

 

[Chuck Leeper]

o2 sensors swapped left-to-right?

I have not checked them. However I questioned the person that is involved, making logs, etc. He says he has verified the wiring is correct....
Several other people have asked the same ?... seems like a common issue, especially with "transplants".

Thanks for your reply.

 

[TurboBob]

unplug one sensor, and see what the data does.

B

 

[Chuck Leeper]

unplug one sensor, and see what the data does.

B

Had to leave the shop, early. Am headed back this am. That test is on my "bucket list"!!

Thanks!

 

[Chuck Leeper]

Well folks, the issue has been found/corrected!
It seems as tho, when the owner did the conversion, he decided to tee the emission solenoid on the truck intake, to the fuel psi reg return line!
I was doing a "brain scan" this am, when I decided to start over, by "staring at the engine."
I traced this hose he had put on the solenoid, and found it went to the rear of the truck. I chased it, only to find it hooked to the hose off the bottom of the fpr..
I then pulled the hose off the sol, and what do you know, it's full of gas.
No wonder the poor old O2 sensors and the STFT couldn't keep up!
Plugged the hose, plugged the sol port, disconnected the wiring, hooked up EFILIVE...WALA! No more issues.
I then made some other changes, reprogrammed the pcm, and made a log of over 2k frames...Nary a hiccup! Drove it.. Runs like a top, will scald the tires.

Life's good!

Thanks to all for the input.

 

[87GNSteve]

Out of curiosity what was it swapped into?

 

[Chuck Leeper]

Out of curiosity what was it swapped into?

87 Chevy 1/2 ton.