Engine faltering at high altitudes.

[aguabonita]

Recently had a GW 2.2 installed in my '87 camper. Broke it in very gently around town and on some small trips.

First major trip to the White Mountains of AZ and it stuttered a couple of times up at altitude (around 7,000 ft I believe). It was cold/snowing when it happend the worst. I actually had to pull over on a hill as the van was totally unresponsive to my frantic accelerator/pedal shinanagons (sp?).

The prob. resolved itself after having turned the engine off and on. But it happened two or three more times thereafter, every time up at altitude. Hasn't happened since reaching lower altitudes. What gives?

Is this a fuel pump issue? O2?
Cheers,
Kev
_________________
'87 Westfalia, GW 2.2, and some other goodies
'90 Volvo 245

[Dogpilot]

Kev,

The first thing I would do, based on my own experience up here at 7,000', is replace the spark plug wires. But they are nearly new you will say! Well so where mine. You do not want to hear all the stuff I did looking for the source of that simple problem. Just get these wires:
http://www.van-cafe.com/vanagon_parts.jsp?pa=p&p=1275393589&pct=199399150&ct=871940227
It fixed the problem. Weak spark shows up under load and especially at altitude. Now if your O2 has been in for a while, like 40+ K miles, replace it as well. The gas savings will pay for it. They go rich with age.
You may want to add a can of this:

_________________
Geology with a Syncro rocks!
86 Syncro Westy AKA "The Bughunter"
98 Disco I
08 Range Rover SC
08 VW Rabbit S
1951 O-1G

[aguabonita]

Thanks for the advice Dogpilot. I will buy a case of the "Dick" ASAP. I figure the faster we burn up all of our oil the better.

Kev
_________________
'87 Westfalia, GW 2.2, and some other goodies
'90 Volvo 245

[singlewc]

[rngr633]

Advancing my timing a few degrees helped my 1.9 run better up here (7000'+ ). Of course, there always seems to be other issues ...........
_________________
" Knowledge is good ". Emil Faber 1904


1984 Vanagon GL
2000 Golf TDI

[reiney]

I'll second the plug wire idea. My '86 weekender was a dog after moving here (Santa Fe) from the East Coast. A bad fuel pressure regulator was making things too rich and the plugs were a mess. New reg. and plugs solved the problem ...

Reiney

[ScottN]

You may want to do a search on "AFM harness" or "AFM fix". I had exactly the same problem as you. It cleared up after installing the factory add-on harness to the AFM on my '87 2.1.

-Scott

[aguabonita]

[tencentlife]

Changes in altitude can be compensated for to a moderate degree by the O2 sensor feedback, but the sensor voltage range is small, so if you make too big a change, it may be more than the Lambda system can accomodate.

Do the O2 sensor, and the plug wires may help, but if you plan on staying at altitudes over 4000' for long, it's worthwhile to make a couple basic tuning changes. General rule of thumb for ignition is to add 1 degree base advance for every 1000' above 4000'. So 3 degrees for 7000'.

If you read in Bentley, you'll also see that the basic mixture setting should be altered according to altitude. See the chart on p.24.52. At 7000' uncorrected idle CO should be about 7%!

You would think that because there is less O2 content in a volume of air, that you would reduce the CO setting to have a similar fuel/air ratio, but the opposite is true. I've found this true in all kinds of cars, carbs and FI; they all respond best to some base enrichment and a little extra spark advance at higher altitudes.

[zohami]

Yep - agree with tencentlife.
I used to live at Kirkwood CA at 7800 feet and drove a 65 bug with a 1300 in it. Going to the valley, at 4000 feet I would just pull over, retard the distributor by hand and enrich the carb mixture. Going back up, pull over at 4000 feet and advance a few degrees and lean it out again.
If I didn't do it it would run very poorly at the other elevation. Once I tried getting it "run right" at 4000 feet, but then it was a compromise up high and down low.
Seems there's less oxygen in the high country, so you have to give the mixture more air, and give it more time to burn.