[Tredicino]

I own a 91 North American base model I bought in 2000. It now has 175000 miles on it with the only major issue being replacing the a/c compressor two years ago. Recently it has begun missing as I cross over a 5000 ft. mountain pass [which I have done several times a year since I bought it], it starts as soon as I go above 2000 ft. and continues down to sea level on the other side and goes away after a few hours. The shop manual says that the Motronic module [controls fuel inj.] has an altitude compensator which is set for 6000 ft. The only way to check if this feature is bad is to swap with another unit out of another vehicle and observe the results. I've done this and the missing has been reduced but is still noticible. Has anyone else had this problem?

 

[Richard2]

I don't know where you live, but are you sure the problem isn't associated with damp conditions at lower levels vs dry conditions at altitude. I also thought altitude compensation was unnecessary at elevations below about 5000ft.

 

[elite38868]

Could be a fuel issue. The last time I drove the 164 up to mount diablo (~3500 ft), the 164 complained on the way down and it ran like crap afterwards for a while. It felt like it was running on 4 cylinders. All of that driving had disturbed the fuel filter and it was pretty clogged. You might be having the same issue.