95 ZJ Two symptoms, what's the problem?

Howard did pass the time by typing:

Just the basics.

- spark (plugs, wires, cap, rotor, and possibly coil or distributor)

- fuel (filter)

High altitude will rob power. And you will feel a loss at 8000 ft but it shouldn't be too weak. When you go to altitude your better off using a lower octane fuel because the higher octane won't ignite as easily with the lower compression. Combine that with a weak spark and your going to go nowhere fast, except downhill in neutral that is. :)

Cleaned the throttle body lately?

Bad gas, dirty air filter, go back to sea level.

Seriously, at 8000 ft you will have lost over a third of your theoretical power (pushing 50% trying to top Vail Pass). I start at

If you lived up here and replaced the CPS, the dealer would give you one that advances the base timing by several degrees. Given the stall at idle, it could also be either a bad TPS or (more commonly) a dirty connector on the TPS that was giving a bad reading at idle and/or WOT.

Just to give you a better feel for the effect of altitude: light a/c, normally aspirated - even with fuel injection - pretty much reach their service ceiling at about 14000 or so.

Hi Will, Back when I was serious drag racer in the sixties we bought engines cast for Colorado to gain a compression ratio running stock classes. This Cherokee build order eludes to the difference still in cars: "Emissions - High Altitude Tracking". Seats - Cloth Low-Back Bucket Luxury Group Trailer Tow Group IV Monotone Paint

A loss of power like every one is talking about is correct. What gas did you put in it? Colorado sells 85 octane (this is their "regular" gas), you might as well piss in the tank at altitude.

It also could be the IAC too.

--James

At altitude, the engine does not need as much octane since the engine's compression pressure at higher altitudes is not as high as it is at lower altitudes. This is WHY lower octanes are sold at higher altitudes.

Jerry

I thought that on those the "High Altitude Tracking" was mostly the aneroid that adjusted the metering rod positions. I guess now (with computer control and FI) that the MAF or MAP sensors wind up doing most of the adjusting thru the computer.

Will Honea proclaimed:

Dunno of any vehicle these days that comes with optional "Denver Heads"

The OP has something wrong though. I get a power loss at high altitude such as crossing the Colorado rockies, Sonora Pass, etc but have never had the stalling, coughing, bucking etc.