Running rich

[Damien1990]

Good morning everyone! I've noticed since I've purchased my truck it's exhaust smells pretty rich when I first start her up and run for a bit. I've got a 2007 LT 5.8 Flex fuel, 65k miles on it. The truck is still warrantied by the dealer, but I don't trust other people working on my vehicles. My question for everyone is what all could be causing it to run rich? I'm not getting any engine lights what so ever... and the smell does seem to go away once the truck is warmed up.

(Stock air intake, no mods, and running 87 for fuel)

Thanks!

 

[CrashTestDummy]

IIRC, these trucks are tuned on the rich side from the factory. That, with colder weather, and first startup, it can be even more rich, and smell so until the thing runs and warms a bit so the cats fire off and the computer sorts things out.

If it's not posting a code, you're probably okay, but it might not hurt to visit a local parts house and have them run a scan on it to see if anything seems out of spec.

 

[CrashTestDummy]

I'll add that while I would expect it to post a code, I have had the fuel pressure regulator blow out on another, much older GM vehicle. We have a 95 Caprice I've put two FPRs on. Both failures caused the car to run rich (even seeing some black smoke out the exhaust pipes on occasion), and both had a ruptured diaphragm. That caused the engine to suck the fuel directly from the vacuum hose going to the FPR. It was easy to test, just pull the vacuum hose off the FPR (which you usually do when checking the fuel pressure with a gauge), and raw fuel will pour out of the port on the FPR.

It might be something to look at.

 

[ccapehartusarmyINF.(ret)]

when you start the vehicle the pcm is in open loop so its basically not checking the pre cat 02 sensors and running a rich mixture after about a minute or two the pcm goes into closed loop and adjust the mixture