'03 Yukon 5.3l Random, intermittent loss of power and stall

[M3mphis]

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

 

[M3mphis]

No thoughts??????????????

 

[M3mphis]

Well, I put in a new fuel pump and cleaned the MAF with MAF cleaner. Drove on the freeway for about 25 minutes. Then it started missing and kind of jerking. Was able to jump onto an offramp and drove it into a truck stop. Left it running and tested the fuel pressure at 43psi. Turned it off. Tested pressure with key on, but not running at 50psi. Truck would not start back up for about 20 to 30 minutes. Then it started right up, and drove the backroads all the way home without a hiccup.

Does anybody have any great insights???? Tomorrow it's going to a pro otherwise.

Thanks.

 

[Rivieraracing]

No codes or check engine light through any of this?

 

[M3mphis]

No codes or check engine light through any of this?

Not a single one.

 

[Rivieraracing]

Sorry, just reread your first post and now saw the no CEL comment!!

Well, you've done alot of what I would do, even replaced the fuel pump and filter which is what I was going to say! The problem with taking it to the dealer with the problem being hit and miss is that if it is running, they may not be able to find the problem without driving it around alot to make it act up!! I'm guessing electrical, possibly dealing with the security feature of our trucks, but that is only a guess from me!!
If I was the one that had done all that you have done to your truck to figure it out, I would be taking it to a professional to get it figured out (and I hate doing that). Can't have it dying out randomly when driving, especially with your wife driving it with the kids in the car!! Good luck with it and report back with your findings!

 

[M3mphis]

Rivieraracing, I earnestly appreciate you responses.

I took my Yukon to my mechanic this morning. They found three codes stored in the computer. Shows what a neophyte I am. I didn't think there would be any codes since the CEL had never come on. They are replacing the crank position sensor, then retesting. I will update this thread with the three codes and the results later on for the sake of possibly helping someone out.

Thanks again.

 

[mnPaul]

Loss of power on 5.3 Flex Fuel 2002

Hi,

I have had the exact same problem on my '02 Suburban.

It seems to become an issue as the weather gets over 85F and also when towing.

Luckily, I live in Minnesota where it never gets warm.

Let me know if the crank postion sensor helps. I have been struggling with this issue for a long time.

Thanks,

 

[rocafella1]

I am also having the same problem with my 02 I also live in mn.......and it has been a heat wave lately my seems to believe it happens when we run the ac for a long period of time please report your findings

 

[strato]

m3mphis,

Have your issues been resolved????? Please update
same problem here. thanx

 

[bdog]

Update Please. Same issues!!!

 

[pstahoe]

I am having the same problem with my 2003 Tahoe 5.3L flex fuel.

 

[bdog]

Update Please. Same issues!!!

Just to give an update, my fuel pump went out. Replaced it and i have no issues now.

 

[Vinniety]

Guys i am on the web right now trying to fix this issue. I replaced my fuel pump a week ago with one from the dealership so im not thinking its that again becasue the same issue i had before i now still have. What the hell can this be!!!!
Update: today I replaced MAF, throttle position sensor and fuel filter. I also cleaned out intake. The truck is running but I didn't take it on a long trip yet still worrying to get stuck. The weird thing is after it cools it restarts.

 

[Vinniety]

Rivieraracing, I earnestly appreciate you responses.

I took my Yukon to my mechanic this morning. They found three codes stored in the computer. Shows what a neophyte I am. I didn't think there would be any codes since the CEL had never come on. They are replacing the crank position sensor, then retesting. I will update this thread with the three codes and the results later on for the sake of possibly helping someone out.

Thanks again.

Did the crank sensor replacement resolve the issue?

 

[Tonyrodz]

I had very similar issues with my 03. Turned out to be my fuel filter--which I read you had changed. The truck drove great and would just randomly die on the highway, back roads etc. No codes. Changed the filter and hasn't died since. Figured I'd put that out there in case someone had similar issues.
Good luck with yours.

 

[bowtie2]

Hello,
Have the same issue on my 2003 Tahoe, stalls everytime after 30 mn drive then need to wait at least 30 other minutes to ccol down, and starts fine.
Did: Put new Delphi sending unit and filter, cleaned throttle body, Map and Mas sensors, new battery, cleaned all ground cable bolts on the engine block and even add a new one.
So I 'd love to read the solution of this very common problem...
Next try: a new crankshaft position sensor.

 

[Vinniety]

Hello,
Have the same issue on my 2003 Tahoe, stalls everytime after 30 mn drive then need to wait at least 30 other minutes to ccol down, and starts fine.
Did: Put new Delphi sending unit and filter, cleaned throttle body, Map and Mas sensors, new battery, cleaned all ground cable bolts on the engine block and even add a new one.
So I 'd love to read the solution of this very common problem...
Next try: a new crankshaft position sensor.

I went to advance auto and asked for every electrical sensor I could think about in the motor area and I changed them. If I remember correctly they were the cam and crank sensors, mass air flow sensor, throttle position sensor and .........I think that was it and never had the problem ever again. 200 dollars for the sensors and well worth it.

 

[bowtie2]

Thank you Vinniety for the update. it's a good way too to solve your problem! There are so many sensors on these vehicules though...
IMPORTANT: About the crankshaft position sensor, did your mechanic had to do a relearn procedure after changing the sensor?
I opened another post on that particular CPS issue I am facing on my 2003 Tahoe. It's on the Engine and drive train thread, and I will also make updates on this one when solved. I am still stuck for the moment, waiting for parts.

 

[Vinniety]

The only thing I did was disconnect battery before I changed the sensors. After all was done I reconnceted the battery made it run for 20 minutes ideling in driveway then went for a 30 minute drive. After that it worked great for two years until I sold the truck.