I live in the Mtns and this winter noticed that my 94 pickup is running extremely rough when the outside Air Temp is around 20 or below. As soon as I drop down into town and the Air temp gets warmer it smooths out and runs fine. Any suggestions?

 

Any codes?

I'd check the temp sensor in the VAF (THA) http://web.archive.org/web/201003261...92volumeai.pdf

 

When was the last time it had a tune up??

Even if you let it warm up it runs poor to you lower your elevation ??

 

Yes it still runs poor after its warmed up if the outside air temp is cold. It's been awhile since a tune up but not a lot of miles (less than 10000). I haven't checked the codes yet, looking for someone with a reader for that year. I was thinking one of the sensors as well. The weather has since warmed up and it has been running great. But I will check the codes and go from there.

 

unless i'm horribly mistaken 'reader for that year' doesn't exist and the code modules for almost all makes and models has been standardized since some point in the 80's. Any auto parts store should have a freebie code reader for you, it helps their sales and helps their customers

 

Oh fer cryin' out loud! This is the one thing you really should have done a little searching on.

Your truck is OBD-1. Which means you use the special service tool - usually called a paper clip - to jumper TE1 to E1 on the diagnostic connector. http://web.archive.org/web/201003261...85diagnosi.pdf

Yeah, you can find a "reader for that year," but electrically it's just a paper clip. Starting in about 1995, all cars went to OBD-II. That's completely standardized, but you do need a reader. That's the kind an auto parts store probably has.

 

O gods! now i remember, yeah Ive done paper clip to resets in my old 80s bmw

 

I tested the VAC meter (thanks for the link) and found it to be faulty. Thanks for all the help. They are a bit pricy $200 + but worth it if it works. Good tip on the paper clip trick for the obd1 reader