S10 Cuts out at High Altitude

I have an S10 pick up that cuts out only at High Altitude. Could it be a Vapor lock problem??

What year and engine? Vapor lock is almost unheard of anymore and is caused by heat, not altitude. You may need to run a higher grade of fuel for your truck to run right. If regular is 85 octane where you are, try 87 or 89. It may help and certainly couldn’t hurt.

There should be a air pressure sensor for the fuel system so check that for a problem.

Higher altitude means lower octane requirements. There should be no need for higher octane fuel.

I suggest checking the vapor recovery system in the car and the fuel pump.

Cutting out usually means a lean air/fuel mixture or an ignition miss. The former can cause the latter.

You really need to provide some actual details about this vehicle.

If the ignition is cycled off and on again the ECM will recognize the lower barometric pressure, advance the timing and recalibrate the fuel/air ratio to compensate.

Even if it’s a 1982?

Personally, I think the year would help.

Picky, picky, picky…

But, if it were an 82 vapor lock would be a possible cause and of course a MAP and ECM would not be a problem. But these hit and miss problem and answer forums can be so confounding. The poster might have thrown out the problem to dozens of similar sights and if the first answer he got took care of the problem we’ll never hear from him again. As I sit here contemplating my book keeper’s conflicting sales tax numbers and wait for the customer to finish test driving the MR2 I read and post and try to keep my sanity. Like my hair, I still have a little sanity remaining.

Sounds good, Thanks for replying!

1994 Chevy S-10 LS V6
Sorry about that.

Thanks for the advice!
Do you think it could be a problem with a MAP sensor? If it has one?

1994 Sorry for the slow response. Didn’t come through my e-mail for some reason.

Any idea where I would find that air pressure sensor? 1994 S10 pick up with a V6

If you began driving with no problems at low altitude but developed problems with loss of power and hesitation, even surging as the road took you to considerably higher altitudes it could be the MAP but as soon as the engine was shut off and restarted the problem would have disappeared since the computer uses the pre-start MAP signal to measure the barometric pressure. If that is not the case with your S-10 throw out some more details and hope for the best.

Here is a little more info if it helps - 4.3 liter v6 engine 1994 Chevy S-10 LS 2wd
Very much appreciate the advice!

It feels like it?s bogging down like it?s running out of gas. If I back off the gas pedal I can creep along in the slow lane at 15 or 20 mph. If I push the gas harder it will suddenly stall out like the gas was cut off. Once it stalls, I let it sit for a couple minutes and it will start up again, but only at a creeping pace. Once I?m on flat land or going downhill it?s fine.

The problem occurs when it is under a load going up hills when I am pushing it. But it has only happened on trips to California, primarily up the hills around Mt. Shasta. On the last trip though it was doing it on hills at a lower elevation. Since then, I?ve driven it around to Portland and up to 5000 feet without problems. No more than a 2 hour drive from here though.

One other possibility - if the fuel pump is close to failing, it might not put out enough pressure, letting vapor lock occur. Might be worth checking that the fuel pressure is correct.

Thanks very much! Does the fuel pressure stay the same or does it change when you accelerate? What kind of pressure would I be looking at?

You should work with a mechanic on this, he’ll need to plumb a fuel pressure gauge into the fuel injection system and look up what the pressure should be. I don’t know.

Thanks again!