This forum has helped me with several projects, so thanks for that. I'm hoping you guys might be able to give me some pointers with an issue that I'm having.
I've got a 2003 Yukon 5.3L flex fuel. Two weeks ago, my wife drove to the next town over. After driving on the freeway for 11 miles or so, she makes her first stop. In the parking lot (the truck suddenly shudders, RPM's up and down, sputtering, then dies. Won't restart, it tries but only sputters and shudders and dies. By the time I get out there (45 minutes approx), it fires right up. I drive backroads and get about halfway home. Then it sputters and dies. Tow it home (thanks, Dad).
I start taking apart the intake. Take the MAF down to the parts house. They test is as being fine with some weird MAF tester (low confidence in this test, FWIW). Clean the MAF sensor and intake plenum. Then I notice the vacuum hose that attaches just behind the intake plenum is off. I reconnect it, put the intake back on. Drives fantastic around town. I thought the problem was solved. A week later, it dies after a 20 mile drive. My wife said this time it did not shutter at all. Just lost power very quickly and died. I checked the battery terminals. One is slightly oxidized, so I clean them up, lube them, and tighten them up. Battery is only like 4 months old. Yesterday, my wife drives to the next town over again. Dies on the freeway offramp. Quickly loses power and stalls. After waiting 15 minutes, it starts back up and she drives the back roads home. Makes it halfway, then it dies. I went and switched rigs with her and the kids. Drove it the rest of the way home with no issue.
I changed the fuel filter and tested fuel pressure at 45psi idling, 49psi on but not running. Went and drove the heck out of it to try to recreate the problem, no luck. Fuel pressure reading the same.
So, I'm trying to figure out where to go from here. NO CEL throughout all of this, mind you. So.......
1. Fuel pressure below spec, barely. Is it too low???
2. I cleaned the MAF with carb cleaner.
Now, I'm reading that I'm a moron and that you should never do that. Should I just replace it to see if that's it?
3. What else do I look at? Without any further insight, I'm thinking of throwing parts at it in an order something like this:
MAF
Crank position sensor
Fuel pressure regulator
Fuel pump
What do you guys think? I'm thinking that the fuel pump is shutting down after getting hot, and it needs replaced. But the pressure readings may be suggesting to look elsewhere???
Thanks in advance, I'm hoping you all might help me avoid throwing too many parts at it. Or at least narrow it down to the most likely parts.
Thank you!!
Matt
I've got a 2003 Yukon 5.3L flex fuel. Two weeks ago, my wife drove to the next town over. After driving on the freeway for 11 miles or so, she makes her first stop. In the parking lot (the truck suddenly shudders, RPM's up and down, sputtering, then dies. Won't restart, it tries but only sputters and shudders and dies. By the time I get out there (45 minutes approx), it fires right up. I drive backroads and get about halfway home. Then it sputters and dies. Tow it home (thanks, Dad).
I start taking apart the intake. Take the MAF down to the parts house. They test is as being fine with some weird MAF tester (low confidence in this test, FWIW). Clean the MAF sensor and intake plenum. Then I notice the vacuum hose that attaches just behind the intake plenum is off. I reconnect it, put the intake back on. Drives fantastic around town. I thought the problem was solved. A week later, it dies after a 20 mile drive. My wife said this time it did not shutter at all. Just lost power very quickly and died. I checked the battery terminals. One is slightly oxidized, so I clean them up, lube them, and tighten them up. Battery is only like 4 months old. Yesterday, my wife drives to the next town over again. Dies on the freeway offramp. Quickly loses power and stalls. After waiting 15 minutes, it starts back up and she drives the back roads home. Makes it halfway, then it dies. I went and switched rigs with her and the kids. Drove it the rest of the way home with no issue.
I changed the fuel filter and tested fuel pressure at 45psi idling, 49psi on but not running. Went and drove the heck out of it to try to recreate the problem, no luck. Fuel pressure reading the same.
So, I'm trying to figure out where to go from here. NO CEL throughout all of this, mind you. So.......
1. Fuel pressure below spec, barely. Is it too low???
2. I cleaned the MAF with carb cleaner.
Now, I'm reading that I'm a moron and that you should never do that. Should I just replace it to see if that's it?3. What else do I look at? Without any further insight, I'm thinking of throwing parts at it in an order something like this:
MAF
Crank position sensor
Fuel pressure regulator
Fuel pump
What do you guys think? I'm thinking that the fuel pump is shutting down after getting hot, and it needs replaced. But the pressure readings may be suggesting to look elsewhere???
Thanks in advance, I'm hoping you all might help me avoid throwing too many parts at it. Or at least narrow it down to the most likely parts.
Thank you!!
Matt
