99 Tahoe Engine Revs

So I have about had it with my truck. I just had a new ht383 put in. Everything is running great with no issues for two weeks. This is completed right before I move from Ohio to Beaverton, OR. So I use my Tahoe to tow my car across the country. Everything is great until 5 hours till the final destination the transmission gives out. So I have that rebuilt. I get the truck back and it is running great when now it is doing something new.

When stopped and the transmission in drive and the foot on the brake the engine after a bit will begin to rev and drop down progressively getting worse until the engine stalls. If I shift to neutral the engine will stay idling and not fluctuate. When I begin to accelerate or am moving down the road I have no issues. I have changed the IAC valve with a Delphi one and that did nothing. Also, I am getting no CEL.

Please help....

I just noticed an unburnt fuel smell. I'm thinking it could be an injector or the fuel pressure regulator. I'm surprised there is no CEL though.

Did you install a new spider injection assembly when you did the engine swap? If you suspect a fuel issue then you should put a fuel pressure gauge on the engine and monitor it. Does your check engine light work? Have you hooked up a scanner to it to see if there is codes stored?

I did not put in a new spider in. My CEL light woks. Another sign that it is a fuel issue is in the morning The truck starts a little slower than normal it doesn't fire up right away.

A slight adjustment of the throttles screw to let the engine idle a little bit higher fixed the problem.