Altitude change issues?

[sbmackie]

OK, so here's the story: Car ran fine for five years out west, first in Salt Lake City and then for the last 4.5 in Albuquerque. Car shipped to Atlanta about a month ago. When picked up from shippers, car started normally, but on drive to house (car fully warmed up) it wouldn't come down off a high idle (like 1400 RPM) unless I lugged it, and then it would stay down. Upon arriving at new digs, I disconnected de-cel valve, and voila, problem solved. So, I twiddle with rubber vaccuum line, check connections, etc, and put car away with decel valve attached. There is STA-BIL in fuel, and Swepco in fuel for injector health.
Cut to today, a month later. I go to start car to give it a bath, and after initially firing up as normal (a glorius sound, just ask anyone in the Road Runner Region), it died. Fired up again, died. Fired up a third time, stumble, stumble, fart, fart, blat, blat, touch throttle, car dies. On fourth start, it stumbled, farted, belched, etc, (didn't touch throttle); I went back and disconnected de-cel valve (kept sealed with finger),goosed throttle, it started to smooth out and respond, I put the de-cel line back on, car now idleing with the idylic lope I'm used to, and throttle response and idle are normal. After washing car, started and ran normally.

OK, so any ideas? Fuel wasn't changed from ABQ to ATL, fuel is 2 points higher in octane hear at 1000 feet. Sure is more humid.

Thanks
Scott

[longhornchris04]

Need car info... specifically the engine year.

If its CIS, odds are it was tuned for Salt Lake's altitude. My car (79 engine w/ CIS) was tuned for LA sea level, and when I went to Big Bear Lake (7000ft) I had lots of trouble... luckily I had the hex key and screwdriver to adjust it. Now, in my case the car was already set rich for sea level... so it was way rich at altitude in the thinner air.

CIS isn't great at altitude compensation, so you car is probably running lean... but because the warm-up cycle involves running the engine rich until its up to temperature, symptoms wouldn't appear until after the car got warm, and go away once cold. Sealing off the decel valve would reduce the air going into the engine... making it run slightly richer, hence fixing the problem.

Do a search for how to adjust CIS, there are several threads out there and its pretty easy if you are patient... or have a gas analyzer. I've done it by 'feel' several times, including after I moved to Ohio.

Oh, and if its not a CIS engine then ignore most of what I posted. Good Luck

[sbmackie]

It's a CIS car. I'll look for some info on adjusting mixture, and see what happens. I'll try parking it until cool and then cranking it again to see if the same issue occurs.

Cheers
Scott