Hogdady

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 CEL was on (DTC PO171 & PO174). Made about a 30 minute trip across town, then condition occurred again, after CEL 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?

transamtom

iTrader: (8)

Power loss at 5000 ft would be normal at that altitude your almost a mile up.

Where did you get your gas? at a sea level station?

They have a different gas formulation for driving in high altitudes.

That could have effected your car.

Hogdady

Thanks for the reply. I'm talking about power loss that eventually stalls the engine. It actually died on downgrade while coasting....went 10 miles with engine off until I could turnout.

blue98Z

iTrader: (29)

Whens the last time you cleaned your MAF? Complete tune up? The 2 codes thrown were because both banks ran lean and you should know that too lean can kill an engine in more ways than one. I highly suggest cleaning it if you havent and inspecting the resistors and the entire unit for any possible damage as well. It shoulda compensated for the altitude change/air change. Thats its job.

transamtom

iTrader: (8)

Good point with both banks lean thats more than likely the culprit.

FORD KILLER

iTrader: (1)

I think you need to put a meter on your flux capacitor and see what kind of gigawatts your making. Just kidding, I'd throw in fuel filter and have your fuel pressure tested. I've seen fuel pumps take a week to finally give up all the way.

Hogdady

Thanks for the reply. I have inspected it but I've never cleaned the MAF. As far as a tune-up, what constitutes a tune-up? Spark plug change? Plugs have never been changed. One thing I did try when I was in Reno was to unplug the MAF and start the engine. Just prior to doing that, the engine would only idle for less than a minute before dying. The response was the same after I unplugged the MAF. I will follow your advice in regards to the MAF and tune-up.

Hogdady

Thanks for the reply. It's a fresh fuel filter. I have a gauge to check the fuel pressure myself. I'm actually considering installing a f/p gauge on the console.

blue98Z

iTrader: (29)

It's simple to clean the MAF. Pick up some MAF cleaner at any auto parts store and remove the MAF from the car and spray the resistors off front and back. You should see them go from black to a like new looking condition. A tune up usually consists of new plugs, wires, cleaning of the MAF, fuel filter, and a new air filter unless it's reusable i.e. k&n. I'd be willing to bet that the root of your problem is just a dirty MAF sensor. They're very sensitive on these cars and when dirty can cause them run funky in every sense imaginable sometimes, but a tune up would be beneficial as well. MAF maintenance is good at every oil change as well.

Hogdady

Thx again for the info. It does have a K&N that hasn't been cleaned for awhile, so I'll give it the full treatment....

Hogdady

A big thank you for all of your help!! The more I read on MAF symptoms, the more it sounds like my issue!

RevGTO

iTrader: (12)

Agree on the MAF and since you're new, I'll point out that over-oiled K&N filters are known to foul up MAFs. You have to extra conscientious about keeping your MAF clean if you're running a K&N.

Hogdady

Thanks for the tip. However, I've been using K&N's since the 60's, so hopefully I've got the technique down by now.....

Cleaned the MAF last night but wasn't entirely happy with how well it cleaned up, so I'm going to replace the MAF.

RevGTO

iTrader: (12)

They didn't have MAFs in the 60's

King Nothing

iTrader: (9)

Switch to paper lol also if the car is poorly SD tuned your car will run like **** in higher altitude's if it was tuned at sea level. Has the car been tuned?

Hogdady

good one!

Hogdady

Help me out here...define tuned for an old timer...

LS6427

iTrader: (2)

He means did you get the car dyno tuned to maximize performance? The PCM gets tweaked to run at its max potential.

Get rid of that K&N....they muck up the MAF's just days after you clean the K&N and re-install it. Rain and any moisture you drive through re-activates the oil on the filter and it goes right onto the MAF sensors, then from that point on you have reduced performance because the MAF gets coated with that crappy oil. Whoever uses K&N filters in cars with MAF's drive around at LESS than max potential performance. Get a paper filter.....I suggest the Mann filters.

A tune on these cars is plugs, wires, air filter, fuel filter, top-end cleaning is good, and MAF/TB/IAT sensor/IAC-valve cleaning. Full can of SeaFoam in 1/4 tank of gas to clean fuel system and fuel injectors. 02 sensor(s) if needed.

$50-$60 and a matter of 1-2 hours. (not including 02 sensors if needed)

Your stalling out part....a failing or bad MAF won't do that after the engine is warmed up.

.

Hogdady

Thanks for the clarification. Can you elaborate on your MAF comment?

LS6427

iTrader: (2)

The MAF is used for cold engine start and WOT....and from what I'm learning from a couple tuners it comes into play at NEAR WOT settings too........so if you're just cruising the MAF isn't going to stall the engine out, not even if it totally fails 100%.

You might want to run this problem by the PCM gurus in the "PCM Diagnostics and Tuning" section.

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