Rough Idle 5.3 fuel flex

[Riordan]

2009 Yukon 5.3 Fuel Flex
After installing a spectre intake my vehicle now runs lean and gives me difficulty starting occasionally. Before installing I a new flowmaster true dual put on and had no issues with only the exhaust. Sometimes throws lean codes P0171 and P0174 but typically at idle or under load, I had the engine light on just a couple days ago and it went away while driving. Even though the light is gone my fuel trim is still definitely out of whack by looking at it using my OBD2 scanner. I've replaced numerous parts including spark plugs, wires, coils, fuel pump and the MAF sensor, 240,000 miles, the fuel filter is in the fuel pump which was replaced. It's happened ever since it has had the intake installed, it has also been smoke tested for vacuum leaks and none were found.

 

[Fless]

Give us a bit more info about your rig: year, miles, are there any engine DTCs, how long has this been happening, etc.?

Does your truck have a fuel filter? If so, has it ever been replaced?

Clean the throttle body with throttle body cleaner.

 

[Riordan]

Give us a bit more info about your rig: year, miles, are there any engine DTCs, how long has this been happening, etc.?

Does your truck have a fuel filter? If so, has it ever been replaced?

Clean the throttle body with throttle body cleaner.

2009 Yukon 5.3 Fuel Flex
After installing a spectre intake my vehicle now runs lean and gives me difficulty starting occasionally. Before installing I a new flowmaster true dual put on and had no issues with only the exhaust. Sometimes throws lean codes P0171 and P0174 but typically at idle or under load, I had the engine light on just a couple days ago and it went away while driving. Even though the light is gone my fuel trim is still definitely out of whack by looking at it using my OBD2 scanner. I've replaced numerous parts including spark plugs, wires, coils, fuel pump and the MAF sensor, 240,000 miles, the fuel filter is in the fuel pump which was replaced. It's happened ever since it has had the intake installed, it has also been smoke tested for vacuum leaks and none were found.

 

[Fless]

I'm suspicious of the spectre -- there may be unmetered air getting in somewhere past the MAF sensor. If you have the stock air filter and tube can you try to reinstall it and see what happens with the fuel trims?

 

[Rocket Man]

This^^^^. If you don’t have the original intake, remove the Spectre, inspect it for cracks or possibly a hole in the tube or anything that can let air in. Reinstall it and make sure the clamps are all tight and the couplers are seated properly. If that still doesn’t work...buy a stock intake and try it. Sure sounds like you have a leak somewhere. What brand MAF sensor did you install? Sometimes the cheap brands cause issues, go with a Delphi.

 

[wsteele]

I am going to go with @Mr.Occham here and say it is extremely likely the Spectre intake is the problem.

Maybe give the Spectre CS people a call.

 

[drakon543]

wasn't aware there was already a thread started for this so since you made 2 threads im going to stick the my next info back in this thread.

aa you can see from these 2 examples. aem has a fairly small tube compared to the others. k&n only necks down the maf section.

airaid haa the beginning and maf smaller than the last piece to deal with the maf.

injen also necks down the maf section to fight the issue.
theres other examples of both cheaper intakes without any provisions and other expensive intakes with provisions for the maf af issue. there has been several work arounds in the past most of which are semi sketch. if you can figure out a way to choke the air back down going to the maf it will help your issue. be warned tho as a maf is fragile and whatever you would use could come free hit the maf or try to get into the tb.

 

[wsteele]

Sounds like the aftermarket induction designers could benefit from learning about a few dead guys whose names ended in vowels...

 

[Riordan]

I'm suspicious of the spectre -- there may be unmetered air getting in somewhere past the MAF sensor. If you have the stock air filter and tube can you try to reinstall it and see what happens with the fuel trims?

I replaced the specter with the factory intake to see if that would clear up my problems and now I am getting a p0455 code and whenever I hit the accelerator sometimes the RPMs stay where I had my foot at after I remove it from the accelerator. Still idles rough I do notice that my exhaust occasionally sounds different then the driver side. ( I have true duals coming from both headers, each are independent.) If it would help I can post what my OBD2 reads for anything needed.

View attachment 271411

 

[Fless]

Post up the short- and long-term fuel trims after warmup, at idle and at 1500 or 2000 RPM.

Also, some of the checks Eric explains might help: