03 4.8: Major engine trouble!

[man_in_blak]

hey guys, my 2003 silverado w/4.8 will start just fine, but idles low and when u put it in gear it just dies out. Has been happening for a while now. Ive replaced the fuel filter, spark plugs, battery and alternator. Any help, cuz I dont know what to do?

[ntrl_spring_water]

ive heard of this a couple times before and i guess it was there torque converter that was bad. maybe that is this case to.at lease check it out.

[J-Ri]

If you idle it up to about 800-1000 RPM with the gas pedal does it still die when put into gear? I'd check the IAC valve if it doesn't.

[man_in_blak]

no, if i gas it up a little it will shift into gear just fine. It didnt use to die when u put it in gear, but when decelerating and manuvering at low speed. Now it dies all the time.

[silveradofirerescu]

Check for vacuum leaks around your intake manifold. Mine would die in gear but not in park/neutral. Also is it giving you any codes?

[j cAT]

Originally Posted by man_in_blak

no, if i gas it up a little it will shift into gear just fine. It didnt use to die when u put it in gear, but when decelerating and manuvering at low speed. Now it dies all the time.

If at idle rpm should be 500rpm..... when you turn steering wheel left right does the rpm stay at 500rpm or does it drop a bit??? if it drops and will not hold idle steady then its a IAC problem.....as this part maintains correct idle as load varies....if the idle is low always and in gear it then it stalls it could be something else ...I would then check codes for some direction as to failure..could also be throttle body carboned up in IAC area....

[man_in_blak]

Thanks for all the help guys, but I fixed it. After hours of research I found that this is a common problem. Everybody consistenly said it was an IAC problem, but there is no IAC on my truck. All I had to do was clean the throttle body well. Note that there were super heavy deposits in there. After I cleaned it ran like a champ. If you guys ever hear of this again on an 03 and up, first pass on this knowledge cuz i know its a common problem thats often misdiagnosed and this is the solution.

[xjcamaro89]

I wonder would this cleaning help any on a 2002 4.8, i have a slight shifting problem that everyone keeps saying relates back to the engine not running right, but i feel it runs fine, i havent taken my Throttle body off and cleaned it, but is that you did, removed the TBI and cleaned it real good?

[man_in_blak]

yup, take it off and use a rag and throtlle body cleaner. Pay close attention mainly to the gunk around where the butterfly would make a tight seal with the inner walls

[xjcamaro89]

Are there any small passages or orfices that should be cleaned as well when i take it off?