truck is stalling out

[Chip93L]

ok, i have a problem. maybe someone can help me. my truck stalls out when i throw it in reverse 8 out of 10 times. the rpms start to go down then up then down and they finally get low enough to stall out. this does it in drive too when im sittin at a light or somthin. and when i am sitting at a light or parked if i put it in 1st it will stall right away. please let me no what u think it might be. i took it to a friend and he said it might be a problem with the trans where if the oil filter in the trans came loose or came off then it might do that because there is a vacuum created when its on and now it is losing vacuum. he said it could be a switch ( cant remember which switch. i have to check) but he put it on a comp. and all the tests showed up fine.

 

[psmith]

A common problem that causes stalling is buildup of carbon and oil in the IAC (Idle Air Control). The IAC is the small cylindrical looking thing that is on the side of the throttle body. You can unbolt it and clean it out with brake cleaner and see if that makes any difference. It did on my 'L. You should see a pintle inside that moves back and forth at the command of the computer. You can reuse the gasket as long as it isn't torn.

Also, you might want to check the PRNDL switch on the transmission. It should tell the computer that the truck is in gear and up the idle speed to compensate.

 

[Chip93L]

i changed the iac and its still happenig and i had someone put a diagnostic test on the trans and nothin came up wrong.

 

[psmith]

Ok, here's another thought. How about the EGR valve. It's not supposed to open at idle, but if it gets stuck open it will let exhaust gas into the motor at idle and cause stalling. You could remove it and block off the plate and see if this fixes your problem.