my wifes yukon has a bad idle problem. it just started a few weeks ago. sometimes it idles fine and then it will start surging up and down. the only codes im getting are p0171 and p0174 both showing bank 1 & 2 lean. I just changed the plugs, wires, fuel filter. I checked the fuel pressure, key on/engine off and I had about 52 psi. idleing it was up just alittle, then when I touch the gas a little the psi jumps up to about 58-60.
it only does this at idle. drives fine other than that.

this is a 2003 Yukon Xl with the 5.3 flexfuel

any ideas of what to check or change?
thanks

 

ok so today when I got home from work, I cleaned the MAF sensor and the throttle body. and so far its idleing fine. no more surging.

hopefully it will stay this way. lol

 

ok, so I spoke too soon. after 2 or 3 days of her yukon running good. it started back up today. surging idle???

anyone have any ideas of what I can check or change?

I did a search and found that the MAP sensor can cause this, can anyone tell me where this map sensor is? pics?

thanks

 

Lean codes and surging idle sounds like a possible vacuum leak.

 

ive sprayed the intake with carb cleaner and no change in idle. but I didnt have a whole can, just used alittle.

and the surge comes and goes. it just ran fine for about 3 days.

thanks

 

Intake gaskets are common problems . Easy to change.

GM has an updated gasket.

 

is there a way I can check them for a leak? I tried spraying some carb cleaner around the intake already. I didnt spray alot cause I ran out.?

 

this problem just started when I installed a new K&N air filter, and I done a few searches and found that some oil from the filter can also cause this problem with the maf sensor.

I just clean the maf sensor on Monday, it ran great for a couple days, (my wife only drives a few miles a day) and on wed. the engine light came back on P0171, and P0174.
the idle isnt as bad as it was before. maybe I got some more oil on the maf sensor?

tomorrow after work I will clean the maf again and see what it does. also might try another air filter.
if that dont work, I guess I will have to change the intake gasket.
thanks

 

still having a problem. cleaned the maf again, and the engine light came back on,
(2) bank 2 lean
(1) bank 1 lean
and it still surges alittle at idle.

any more ideas?
thanks

 

I am finally gonna have a day off this weekend so I will have some time to work on her yukon.

anyone have any more ideas I can try. I cant afford to take this thing to the dealer to get it figured out.

thanks