2004 Suburban 5.3 rough idle / misfire

[jimmycinla]

Vehicle: 2004 Suburban Z71 4x4 180k.

 

So, I have an issue when the outside temperatures get warm I have a rough idle / misfire happening on start up for a few minutes then it goes away, vehicle does not throw any codes.

This only happens when the outside temps start to get warmer in the summer (Southern California), todays temp is low 80's and its happening.  This happens on initial start up and also after engine has warmed up,  Example: If I go out an start my vehicle at noon and it's hot out it happens. I can drive to where I'm going, turn vehicle off, then come out 10 minutes later and it happens again on start up.  If I were to go start it at 7am or 9pm when its  cooler outside it doesn't happen, it also doesn't happen all winter long with the cooler temps.  So it's something that is affected by outside temperatures.

Happens regardless of fuel level in the tank. All fluids are at the proper level.

 

 

My questions is what could be directly affected by outside temperatures like this ?

 

Things I've done (all new ACDelco Parts):

 

1. Fuel Pump

2. Vent valve & Vapor canister

3. Coils, Plugs & wires

4. Coolant temp sensor

5. Removed and cleaned throttle body in detail

6. Mass air flow sensor

 

 

Thank you in advance !

Edited June 28, 2022 by jimmycinla
add temp

[Jsdirt]

Regardless of what was replaced, I'd get a fuel pressure gauge on there to see what fuel pressure is doing when the problem happens.  Could be a lazy under hood relay in the fuse box that gets sticky for whatever reason in higher temps, or the new pump has a bad check valve that isn't working right in elevated temperatures due to bad tolerances.

 

At least if you see you have low fuel pressure, or that pressure bleeds off whenever the engine is shut down, you can now focus directly on the fuel system instead of firing the parts cannon at it. 

 

I had a similar problem with my '07 years ago after I dumped about 5 gallons of stale premixed fuel from several chainsaws, boats,  and other outdoor power equipment in there. The problem lasted for 3 months, then went away. Only thing I could think of was some trash got into a few of the injectors and took some time to finally break through and get burned up in the combustion chamber, or they were just sticking for whatever reason the stale fuel introduced. So you could have sticky injectors from the heat as well. Might just be worn out with age. An injector balance test could narrow that down.