Rough Idle, Not Starting With Low Fuel

[lkrasner]

I Have a 2002 Tahoe LS 4WD with the 5.3 Flex Fuel engine. About 265,000 miles on it.

This problem has been going on for quite a while now, and has never caused a huge issue, but I want to get it dealt with. If I let the car sit overnight with less than a quarter tank of gas, it won't start. I can hear the fuel pump make a noise like it's kind of sucking air, and sometimes, if the situation isn't too bad, I can turn it off-on-off-on a bunch of times to run the pump, and it will start. Once running, there is no problem, I could run it out of gas no problem with no effect on the idle or performance.

The tuck also Idle's a bit rough. not stall out kind of rough, but lurching when idling in gear kind of rough. It's noticeable, but not so bad I'm worried about it dying. It also intermittently throws 2 error codes: P0171 and P0174, Fuel trim system too lean banks 1 and 2. This goes on and off every few days. I also occasionally get the flashing MIL with a random or multiple misfire code while idling. All the codes happen way more when it is cold out. Idle is maybe a bit rougher too, but not much. The starting problem seems independent of temperature.

I've replaced the fuel filter with no change, spark plugs are new a few years ago, had the injectors cleaned at the oil change place. It was a fuel additive and something they were spraying into the fuel line by the engine. Not sure what it was, but I figured it was worth a shot. How hard is it to pull the injectors and really clean them myself?

I tested the fuel pressure when it was running normally, and it was normal. I'm yet to test it while acting up. Any ideas here? The not starting makes me think fuel pump, but the other symptoms don't seem to fit that. This has been going on for over a year now as well.

 

[clandr1]

Check the fuel pressure under load - you'll need to either rig up a pressure gauge where you can see it while driving, or an alternative is to "power brake" the truck while staying stationary so someone can read the gauge while under load. Sometimes the fuel pressure looks fine under idle, but won't as the truck goes down the road.

Sure sounds like you need either a fuel pump, or a fuel pressure regulator (which may or may not be integrated into the fuel pump itself).

 

[nikogto]

There is a TSB on this, my 2003 is doing the same thing. #04-06-04-012C. Replace the fuel strainers, there are 2 of them, one on the main module, and one on the pump itself inside the plastic housing. You'll have to drop the fuel tank and remove the pump/module to replace, do this with low fuel in tank, drain/strain the rest of the fuel into empty gas tanks and flush out your tank and dry good. Sediment collects on these strainers and when the vehicle sits for periods of time at that fuel level, it blocks the fuel from the pump. On your lean codes and rough running, you need to replace you intake gaskets, very common on these motors. The colder out it is, the more they suck air till the motor heats up. You'll want to clean up both knock sensor areas also, and seal the rubber covers to the inspection cover to keep water from getting in there and corroding the sensor plugs.

---------- Post added at 11:37 AM ---------- Previous post was at 11:36 AM ----------

almost forgot, here is the part number 19122083 from the dealer, price is $53.20