Out in Grand Junction, CO. Altitude is about 5300 ft high. Made it thru Nevada with no problems but Sat morn engine would not rev over 2500rpms, chk engine light came on, and gas mileage dropped off drastically.
Im getting a 44 code, which is the O2 sensor detecting a lean condition. I expected that with the thinner air that I would be running richer. Couldnt due much chking other than noting the O2 sensor had the 2 wires connecting it.
Does this sound like an altitude problem that will clear up when I get lower?
Is there anything I can do in the meantime to alleviate this problem. Was planning on going higher into the mountains but with the car running like this it would be difficult to maintain the speed limit on a long incline.
theres hardly any power at WOT...........just a continuous bog.
Any suggestions appreciated as Id like to continue my vacation.
Stock 1981.

 

OK.....did a search on high altitude tuning and a couple solutions mentioned where advancing the timing and/or run a higher octane fuel. Cant see how either of these will correct a lean condition. Using 87 octane gas now. u
Unless this condition is not related to altitude. Sure could use some help here, guys.

 

It's possible that the O2 sensor is actually stuck reading lean, normally in this case the engine would run rich. Is it blowing any black smoke?

:cheers:
Pat Kunz

 

I would get it checked out, or burn some 91 real quick. a lean mix is horrible for an engine. it can burn pistons, valves etc... where do you usually drive your vette? what alt? i know that some times its a shock to those old computers when you change alt. also i had an 85 Trans am with a rochester computer controlled carb. we had to have the carb re jetted for the high altitude, because we found out it was still set for new jerseys alt.

 

Not blowing any black smoke out. Usually drive the car in Oregon which about 1000 ft. Kinda hoping its not really running lean since I already put bout 300 miles on it while the chk engine light was going on and off. Im stumped. This just happened over night. Was great driving thru Utah, but in the morning this condition started.....anymore ideas?

 

ottasite,

Grand Junction was Low altitude where I came from. I lived at 8200' and would love the performance gains realized when coming down to Denver's mile high! Don't bother with jet changes for vacation. Ideal jetting is only a couple numbers from sea level anyway. The biggest difference is ignition timing. You need to advance the timing about 1 degree for every 1000 feet of elevation change.

Because the air is so much less dense than at sea level, less oxygen, the mixture takes longer to burn and you have to give a good head start. The carb really takes care of itself for the most part. Thinner air pulls less gas through the nozzles and that is as it should be. If you don't change the timing, run lower octane fuel. High octane fuels burn more slowly than low octane. If you use high octane, you make the problem even worse. You will backfire through the mufflers every time you go down a hill. This is the result of all the unburned gas entering the hot muffler.

Mark your distributor before you leave and take a 9/16'ths distributor wrench. That's what I did when I made my many trips back to Chicago. But remember, even tuned to a razor's edge for high altitude, you are losing a big percentage of your horsepower. I think I was something around 35% less than sea level above 8000'!

There is also the strong liklihood that your O2 sensor chose this time to fail and has nothing to do with the elevation change. But this does not change any of the stuff I spoke about above.

Chuck


[Modified by Chuck Harmon, 2:56 PM 5/19/2002]

 

Just as something to try out, Try disconnecting the O2 sensor harness. This should default the ECM to a fairly rich open loop mixture and see if it runs any better, if it does then change the O2, if it runs worse then the chances are it's not the O2 sensor.

:cheers:
Pat Kunz

 

Wel, thanx for all the suggestions. Replaced the O2 sensor and that seemed to cure the chk engine light.............44 code. Now just have to tolerate the high altitude problem. Hard to diagnose a problem when two things go wrong at the same time. Now I can continue on my vacation. Thanx again for the help.

 

Like the man said, you need more ignition advance. I run at high altitudes all the time, from 4000 to 8000 feet. I would also use the best gas you can get. If you see a "Sinclair" station, get their premium fuel, probably 91 octane, and set your base timing up to about 12 degrees BTDC. Sinclair gas is made in Wyoming, formulated specifically for the altitudes and temperatures we get in the Rockies. Really, any premium would be fine, but I believe Sinclair's the best. The extra octane will give you some latitude in terms of the advance so you won't have to worry about knocking. Good luck, enjoy the mountains!
:seeya