Please let me know if you checked for trouble codes and what they are. There can be stored trouble codes even if the check engine light does not come on. I think we should start with checking the fuel filter and fuel pressure. If the filter is clogging it will cause a lack of power and even cause the vehicle to quit. Many times if the filter is clogged it will take out the fuel pump. The fuel pressure should be 48-55 psi.
lets start here. I would do a quick check on the fuel pressure regulator, remove the small vacuum line and check for fuel. If there is fuel on the vacuum line the regulator is bad. It still may need a pump.
let me know what you find
Forgot to mention that I did change the fuel filter about six month ago as well. Will check codes again with my obd II tomorrow, but as I said, I had no codes. Prior codes a year ago showed knock sensor and o2 sensor. GM dealer ran it through their code readers at $150 and told me to replace cats, did and still running into problems. Will check fuel regulator and pressure in morning and get back to you. Thanks.
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checks for codes, clears codes and shows live data
Hey Ironmike, Ran a check today on the fuel pressure and came up with 52 psi when it was priming and while idling it was measuring 44 psi Seemed to be ok. I had no fuel on my vacuum line to the regulator. As I mentioned before, fuel filter was replaced 6 months ago. Have never had it die on me in town. Always after driving for a few hours on highway and under a half tank or so of gas. Will stall out and restart within 5 min and run rough for some time, but clear up after a bit. Last time it struggled and wanted to die under load going up hill as well as in bumper to bumper traffic. Fuel pump is original with 250000km Don't want to spend the $300 plus if it is a shot in the dark. What you think? Also, no codes came up!
I would hook up the fuel pressure gauge and run it under the wiper arm with the hood open just on the safety of the latch. I have driven vehicles like this and was able to confirm losing fuel pressure.
You could also do the driving and get the vehicle near to when it fails and then hook up the fuel gauge and drive.
I would make sure this is not fuel related.
Next I would clean the MAF sensor. They can get contaminated and as the hot wire inside heats up the contaminates act as insulation. Most parts stores sell MAF spray cleaner.
Have never replaced MAF sensor, but have cleaned it big time. As far as running it with hood opened but latched or checking fuel pressure after it fails. One, I got a mechanic to check fuel flow pressure for me this am since I didn't have the tool and it cost $65 and he did it for $20, so don't have a handy meter. On running it until fail. It would take about 8 to 10 hours of driving to get it to fail. Never happens with local driving. Always during a long trip. I know your giving me your best, XXXXX XXXXX is your gut feeling on this?
My gut is the fuel pump is failing. I am guilty of this myself, running the vehicle with 1/4 tank or less leaves more of the fuel pump out of the gas. The gas helps the pump run cooler when the pump is submerged.
I hate to replace parts without confirming
Thanks for your help Ironmike, will look to change out fuel pump and hope we hit the problem. Only time and next long trip will tell :( Do appreciate your input and will let you know if she fails after repair.
Hey, Ironmike. One last question before I swop this out. When you restart with a bad fuel pump, can vehicle run rough for some time and clear up after you top off gas again. Does this keep it running cooler?
Could be a leak at the pump and or the pump working better with more fuel to cool it down.
thank you very much