1980 SC - idle "hunting" and stalling - Altitude?
 

I went to see a 1980 SC today with a buddy.

While the engine started fine, the idle began to "hunt"- going from idle to near stall and back.

This car has recently moved to Denver's 5280 altitude from Florida, and the seller says the fuel injection must need adjustment for altitude.

I drove it, and it stalled unless you kept the idle up....Is the seller's explanation ridiculous, or with merit?

Either way my buddy would get a PPI, but I had to ask.

Thanks - Dickson

Sorry... was it equipped with an aftermarket electronic fuel injection or OEM delivery? You can usually tell by how the engine looks. OEM has the black plastic filter over and behind the fan. EFI usually looks pretty empty behind the fan. Often you will see modern fuel rails running from front to back on both top outer-edges of the motor. Did the owner mention megasquirt? There's a big difference in how issues are diagnosed for EFI.

Vacuum leak.

WUR may not be getting power to warm up or it could be bad. anyway, fuel pressures need to be checked first or at the least it could just be lean from alt. if it is so simple, why did he not have it done if he is selling it?

i would count on the WUR being bad and have to completely go thru the CIS and replace things that leak air, like Orings, injector sleeves, rubber boots just to name a few.
i try to count on the worst when buying a car.

As far as I know the FI is stock but who knows. The car does have some track history and "race" mods like heavier suspension, upgraded brakes. We will see - but a PPI is a certainty.

It would be running rich if it went from FL to CO. It will idle hunt from running rich, and it will most certainly need an adjustment from being up here. It might have been out of adjustment in FL, and the thin air up here might just be making it worse.

That said - idle hunting is a symptom for a lot of problems.

Way too rich, re set the CO...very common if it was on the rich side at sea level it will be way to fat for that height

That's one of the problems with CIS injection, it's unable to compensate for changes in altitude effectively. From sea level to anything above 3500ft I would always have lean it out to regain performance on my 78 3.0.


Cheers,

Joe

I don't have a problem if you balance it. I drive from Phx to about 5000 ft regularly without issue (9.8 comp).
Lots of folks have fattened the CO for cooler running and detonation safety with the higher compression numbered cars. Take that to a much higher altitude and it's just too rich at idle.