Hey I’ve been having this problem for a couple weeks now since weathers been heating up here. Engine is a 2006 5.3 L33 DBW. It’s a swap engine into a 1992 C1500. Transmission is a TH-350. I’ve done all the work so I’m familiar with how everything was done.

Truck starts great in the morning, good idle, and drives great under acceleration, cruise and WOT for the first 25-30 mins. Usually it drive just fine, has a good tune. Anyways, drives normal until the truck reaches operating temp and the engine bay gets hot. Once the engine is hot, every time I let off the pedal coming up to a stop or at low speed the engine idles really low (200-500 rpm, 750 idle set at), and truck starts shaking violently and tries to stall, sometimes it does. Starts right back up if it does. Once i give it gas it accelerates/drives fine again until the next stop. What’s the cause?

Parts that are new within last year:

Maf (cleaned recently, dry air filter)
Temp sensor
Map
Spark plugs/wires
Alternator
Battery
Intake Manifold gasket- felpro
VSS- dakota digital th350 to LS pcm
O2 sensors
Vacuum hoses
Fuel filter/Pressure regulator
Fuel pump 340lph- Holley
(Everything Ac Delco/Delphi unless listed otherwise)

DBW Throttle body isn’t new, but was cleaned within the last couple months. May have some oily stuff on it by now.

I’ve researched for two weeks and tried seemingly everything and fixed nothing. What do you guys think could be causing this? I can clarify anything if you need more info. Thanks a bunch!

 

Stock cam?

 

Not stock cam, has a btr stage 3 truck cam. it’s worked great on its tune up until now. I may be ignorant in saying this, but I didn’t think the tune would start running weird unless a part was failing/vacuum leak. Just having troubles finding the issue. Cam is definitely making the issue feel worse that’s for sure!

 

I say vacuum leak. Smoke test that thing

 

If you're staying with the LS platform it may be time to buy HP Tuners and a wideband. The parts cannon didn't work so someone needs to evaluate some data logs.... you're stumbling in the dark.

 

I agree. A datalog will tell atleast part of the story

 

Have you checked the grommet for the vac sensor? Mine was worn and was letting vacuum escape with my BTR stage 3 it was idling like crap. I vote vacuum leak.

 

If you haven't had the setup thru summer months before, ambient temp effects several timing and fueling tables, so could be in the tune. As previously mentioned, a good data log will likely point out the issue.