Vortec help please

[Magikal]

7.4l vortec from 1997 c3500 in my k5. Standalone harness and pcm tune by team208motorsports years ago. Suddenly started running like crap. Barely feather it to keep running. Spit and sputter for a bit and then click, runs fine for undetermined amount of time. Hooked up scanner and noticed intake air temp was reading -40. Unhooked sensor. Same. Jumped plug at sensor and went to+150. Ok, sensor is shot. Ordered new acdelco sensor and installed. No change. Still reads -40. Wtf? Help please.....

 

[Bent77]

I’d start by making sure you’re getting proper voltage to the PCM, then test grounds

 

[ZooMad75]

7.4l vortec from 1997 c3500 in my k5. Standalone harness and pcm tune by team208motorsports years ago. Suddenly started running like crap. Barely feather it to keep running. Spit and sputter for a bit and then click, runs fine for undetermined amount of time. Hooked up scanner and noticed intake air temp was reading -40. Unhooked sensor. Same. Jumped plug at sensor and went to+150. Ok, sensor is shot. Ordered new acdelco sensor and installed. No change. Still reads -40. Wtf? Help please.....

Whenever I've had a temp sensor reading show -40 it's usually an open circuit. IF the PCM thinks it's actually that cold it can be dumping fuel to enrichen it for warm-up.

However, I'd be more suspicious of the harness going to injectors and items from the short harness under the upper plenum. That harness usually isn't provided with a standalone harness. That harness gets cooked under that plenum and can cause all kinds of problems. The other problem area is the coil and ignition control module as they can quit when they get hot. Since they are both bolted to the back of the upper plenum they don't get a lot of airflow and can get cooked pretty well too.

 

[Magikal]

Whenever I've had a temp sensor reading show -40 it's usually an open circuit. IF the PCM thinks it's actually that cold it can be dumping fuel to enrichen it for warm-up.

However, I'd be more suspicious of the harness going to injectors and items from the short harness under the upper plenum. That harness usually isn't provided with a standalone harness. That harness gets cooked under that plenum and can cause all kinds of problems. The other problem area is the coil and ignition control module as they can quit when they get hot. Since they are both bolted to the back of the upper plenum they don't get a lot of airflow and can get cooked pretty well too.

I'll check it out. Any easy diagnostic procedures for it?

 

[ZooMad75]

Tell me the codes you got and I can email you the diagnostic procedure when. I get home from work tonight.