Help with engine stall at low rpm!!

[WayneJ]

Ok so I've gained progress....with my map sensor disconnected the truck will idle (rich) but won't die out or stall. So I took the map sensor off of my old motor and plugged it in.....problem returned. Idles for a while then dies out. Any ideas?

 

[someotherguy]

Have you looked further into the fuel pressure issue? Because I'm telling you, 20psi is way, way wrong. Either the pump is wrong, or there's some other issue, or the gauge is incorrect/faulty.

No stall with rich mixture due to disconnected MAP / stalls with MAP connected kind of points to a lean mixture or possibly marginal fuel pressure, but you've got such a mixed bag there it's really hard to diagnose long-distance.

Get a different gauge to check the fuel pressure with, because that 20psi is a red flag.

Richard

 

[WayneJ]

I

Have you looked further into the fuel pressure issue? Because I'm telling you, 20psi is way, way wrong. Either the pump is wrong, or there's some other issue, or the gauge is incorrect/faulty.

No stall with rich mixture due to disconnected MAP / stalls with MAP connected kind of points to a lean mixture or possibly marginal fuel pressure, but you've got such a mixed bag there it's really hard to diagnose long-distance.

Get a different gauge to check the fuel pressure with, because that 20psi is a red flag.

Richard

I do plan on re checking, but that poses some issues. 1-I'm fairly sure the gauge is faulty because it was at a hobby shop on base, and all of their tools are on their last leg, you can tell it's been beat, the glass was even missing. 2 - the tbi doesn't have a schrader valve so I can't check it with the engine running, which is ideally the best time to check it. it only stalls after it's been running for about 30 sec. So until I find a 3 way fitting that I can hook up im kind of at a loss with that. I also noticed that the vacuum line off the egr valve is gone so I'm going to find one and see if that helps. It really is a mixed bag here, taking a truck I've never seen run, then putting a good used power train...lots o variables... But thanks for all the help Richard

 

[someotherguy]

http://www.chevytalk.org/fusionbb/showtopic.php?tid/253427

A little further down in that first post is info on using a gauge on a TBI.

Richard

 

[Justin S]

However when at a stop in any gear except nuetral, or barely on the throttle it will sputter and die. And it's getting worse.

There's a chance you're having torque converter lockup issues, If you're coming to a stop, and it stalls, it could be the TCC solenoid or something, popping in neutral would cause it to not stall.

 

[WayneJ]

I thought about tc lockup, however once I ran it more i dispelled that idea because i can still drive it to work. It only happens when I'm not on the throttle, and it happens faster when under a load, aka in gear. But now that I have the map disconnected it doesn't happen at all

 

[Justin S]

so when it does it, it stalls shortly after letting off the gas, while still rolling at a high speed?

 

[WayneJ]

Only while off the gas, or slowing down. Same as when in nuetral. I'm positive this isn't caused by a mechanical issue with engine or transmission. I pulled them from another 94 and saw them running/shifting strong. And I know I put the tc on correctly (all clicks). It's gotta be an issue with air/fuel/emission control from the truck components. Just have to narrow it down.

 

[Justin S]

just curious, did you swap over computers, or are you using the same one? Just throwing this out there since it wasn't mentioned, but is this a 4.3. 5.0, or 5.7 and i'm assuming you checked to make sure you put the same thing in that you had before if you did reuse the computer?

 

[WayneJ]

Yeah 350 for 350 swap same pcm