Need Help With Rough Idle!!!

[KWIKNVA]

Hello,

Ok, I have a 09 Yukon XL 6.2L that has a rough idle when cold started. Takes about 6-10 sec for the idle to smooth out. Basically it's runs like I have a cam with a 112 LSA. Now I have codes P0175 & P1400. Note P0172 & P0174 are showing in the history. I've read a few threads that have me thinking bad O2 sensor(s) However, I've read intake gasket leak to to much alcohol in the fuel. The truck is bone stock so no CAI or K&N filters.

If anyone has a solution please share or any ideas that may be causing the issue. I think my first step is to clear all codes and see what code returns first.

Thanks for looking

 

[bullitt4423]

If it goes away when warmed up I would suspect intake gaskets. Usually difficult to test without a smoke machine. From a cold start, spray carb cleaner around the intake gasket while it is idling rough and see if it smooths out.

 

[KWIKNVA]

I reset the codes and removed and cleaned the throttle body. Codes P0172 & P0174 came back almost instant. Same rough start. Next I'll clean the MAF which looks like it time for a few squirts of cleaner. I want the issue to be bad O2 sensors due to making this a easy fix however I'm starting to think my fuel pump maybe the cause. Seems there is a check valve that helps the pump maintain pressure when not running???? I must have a leak there inside the tank. Would explain the hard or rough start and smooth idle once running for 10sec or more. This condition is a cause for the codes as well.

Anyone ever had this part go bad? Check valve or fuel pump not keep pressure?

Like to know if this a possibility before I buy a 250.00 pump and drop this big A$$ tank.

 

[KWIKNVA]

Ok, so far so good, the now clean MAF sensor has the idle smooth with no lope at cold starts and no codes. $8.00 dolla fix.