Question for a friend. It's a 2000 suburbon with a 5.3 liter in it.

The problem is: It has a very eratic idle after sitting over night and is much worse in cold weather. He says it revs up after cranking, then drops down to the point of alsmost dying. After it reaches operating temp, it acts fine. He said the shop changed the fuel filter and cleaned the injectors. I think it may be the idle air controler. Any help and prices involved.

 

try the fuel pressure regulator and check and see if its leaking we see that here alot

 

does it puke any black smoke when it initially starts? has it been modified in any way? if it revs after starting, it doesn't sound like a rich condition but rather a lean one. it almost sounds like the ECM program has gotten corrupted somehow. does it do this everytime it is started or just the initial morning start? have they scanned the truck? bad ECM temp sensor?

 

I'm having the same issues. the idle will vary a few hundred RPMs while cold. Kinda sounds like it's loping. I'm not too worried about it, thinking it's just a product of cold weather and the TB bypass or intake mods.

Won't the fuel pressure regulator cause the truck not to start until it is "primed"? I had that issue while under warrenty.

Less than 10k on a fuel filter here...

Here's a list of possiblilities: Engine checkout

 

Check the TPS and IAC connectors on the TB. I would start there and then check out the flash. It could be a MAF too I guess.

Does it do anything wierd when it's warm?

 

the regulator leaking would cause a rich condition initially, but should clear up shortly after starting.

 

the tps and iac would most likely set a code. now the iat may also be giving a false reading too. that's a thought.

 

After it's warm, it's fine according to him. There have been no codes and it is not modified in any way. This thing still probably has the factory air in the tires. That's how un-modded it is.

 

Its it a 2000 and he hasn't done anything at all with it, it could be as simple as the platinum tips having fallen off and thats causing the roughness. My vote goes to plugs and wires.

 

what about the headlight fluid?

so does it smoke on startup at all? how many miles are on it?