Hogdady

I posted this in General Maintenance and Repairs and a member suggested I post it here. Was starting to think I had MAF issues, but he says otherwise. Can anyone offer comment?

Vehicle normally operates at sea level. Made a 3 hour trip to a max altitude of 7000 feet, then spent a few days at 4500 feet. Condition occured about 2 hours into trip at about 5000 feet. Gradually started losing power up until engine died. Restarted after a few minutes, but experianced power loss and stalling for the rest of the trip. No codes set during this period. After car sat overnight, engine started and ran fine. Observed that SES was on (DTC PO171 & PO174). Made about a 30 minute trip across town, then condition occurred again, after SES had gone out. Went back to sea level next day with only one incident of power loss on the way down. This condition occurred once before awhile back (8-10 months) in stop and go traffic on about an 85 degree day. Vehicle has a relatively new Walbro fuel pump I installed when it only needed a f/p relay (duh). I'm a 35 year diesel engine mechanic, so I'm not totally ignorant, but not much experiance in gas electronics. I have a code reader, but no other electronic diagnostic tools. Can anyone offer some advice?

Here is the thread >>https://ls1tech.com/forums/general-m...ower-loss.html

2xLS1

iTrader: (25)

P0171 and P0174 are lean codes. Fuel trims over +20%. Put a fuel pressure gauge on the rail. S/B 58 psi. I've seem many times on self installed pumps the hose between the pump and the top of the pump assembly fail.

Hogdady

I haven't checked f/p in a while, but I did have the pump out last summer and changed that hose while I was there. I will check again to be sure. Thx.

2xLS1

iTrader: (25)

If the fuel pressure is OK then check for a vacuum leak downstream of the MAF sensor. The little hose between the PCV valve and the intake manifold is prone to rot and leak. Another cause of lean codes is a dirty MAF sensor. Also on the fuel pressure, I've see it be ok at idle and drop under higher fuel demand. If your FP tester has a long enough hose, tape it to the windshield and go for a drive.

Hogdady

Thx again. I will thoroughly check for any vacuum leaks. Another member stated that the MAF sensor could not be responsible for the symptoms I experianced once the engine is up to temp. Any thoughts on that?

2xLS1

iTrader: (25)

The MAF sensor could be 100% responsible for high fuel trims. It is high fuel trims causing the 2 codes you mentioned to set. It's just not the only thing, but could be.

Hogdady

Could the MAF also cause the stalling and severe power loss I experianced?

popethe5th

iTrader: (2)

use a can a brake clean to find vacuum leaks when you spray the leak idle should increase because your not running rich instead of lean obviously. just my 2 cents