High Altitude Performance Problem?

[vwzzuk]

I just got back from a 3 day trip that took me from Portland to Colorado Springs and back.

I noticed performance issues when the caddy reached high elevations, such as, above 7,000 feet and above. It would act as if it was missing at speed resulting in bucking a little on the freeway and miss when idling. It only would do this around the Laramie/Cheyenne/Denver areas. When I first got to Denver, I checked all my lines, changed out my fuel filter and determined if everything was restriction free on the feed and return lines. Everything was good.

Has anyone else experience this problem with their 1.6NA before?

My Pickup lives in the Portland, OR Metro area and never has missing issues at Oregon/Washington altitudes... including in our high desert(5,000ft). Motor is a 1.6NA Engine in great shape, that is, its been rebuilt (head, injection pump and block with new pistons). Engine has around 10K on the rebuild and doesn't use a lick of oil.

Any thoughts?

[8v-of-fury]

An extra 2000 feet is probably enough to really starve it for air being that it is non-turbo.

[libbydiesel]

I've been up and down from 0 to 10,000 and I live at 7,000 and on a non-turbo altitude will decrease performance some and increase max fuel smoke but it won't cause any bucking or missing. 

[8v-of-fury]

I only live at 754.593 above sea level lool, I have no idea what the affects of thin air are.

[wolf_walker]

I've been up and down from 0 to 10,000 and I live at 7,000 and on a non-turbo altitude will decrease performance some and increase max fuel smoke but it won't cause any bucking or missing. 

This is correct, there is another fault.

Altitude will make a NA diesel feel like an absolute slug if there is not a compensation device on the injection pump, and even then it isn't doing one any favors.

[vwzzuk]

Still no issues. I guess I need an elevator that goes to 8,000 feet so I can run it and see if the same results show up.

Any suggestions to look at if its not altitude related?

Dirt in the fuel screen in the tank, sticking injector, bad injection pump, air in the lines, ?

[wolf_walker]

Do you have the clear feed line to the pump still?  It's a good place to watch for air, air seeping in will do weird stuff.
Generally it takes a lot to make a diesel miss, it's usually something pretty obvious.  You got a weird one there.
Damned if I know how to emulate an altitude problem, restrict the intake? Thinner air up high.  Bout all I got.
If it's fine around home and isn't smoking or starting hard or getting bad MPG, and you don't go up high often, I'd
leave it be.  It'd drive me nuts, but I would.

edit: check the tank vent system, I've had them clogged up, might be an issue with long trip elevation changes, did you
fill up while up high?  That still does not really count for a miss-inducing problem in my experience.  Bad fuel?
I picked up some biodiesel blend on the road before that I wasn't prepared for, and didn't notice(blame sleep deprivation), and had to swap out a
fuel filter shortly after, that stuff cleans out gunk quick. But again it was a loss of power thing, not missing.  Diesels don't miss unless something
is really wrong, and it usually does not fix itself unless it's a sticking injector(s) or pump.

[CRSMP5]

how much coal does it blow in low alt areas?? if allot.. id say too rich when air thin..

ever time ive been to denver has been td or last tdi-m.. jacks oil temps up by 12*c or so, water temps go up... and egt took hard hit this last time.. when going west out of denver.. no do that ever again.. south/north no issue.. but west towards vegas.. not good..

if you soot good.. back off the soot screw see what happens.. also adv knob change anything?

[vwzzuk]

Yes, I still have the clear feed line at the pump. There were no bubbles that I could see. Even when I put a flashlight to the line. Advanced knob made no difference other than the usual purpose of making it start easier when in a cold environment. I crashed in a hotel in Laramie and it got down to 10 degrees or so. Took a while to warm up.

Its got normal soot output, nothing unusual. I drove a 60 mile round trip to work and back last night and it ran great as usual here in Portland.

It did however push out black up Wyoming hills under load (I was carrying 1,100 pounds back home). But I expected that. Never overheated, never ran hot. It was cold out too which I'm sure helped alot. I'm not sure how it would go in July. I'm sort of anal about keeping it cool so its got a good cooling system.

The funny thing is my son and daughter drove the same route to the same location last year during December. They experienced the same symptoms in the same areas around Cheyenne. I expected to drive out there and put another injecting pump on the rig. But the problem disappeared, just like my trip last week...Weird. Just pulling my hair out trying to get to the bottom of this.

I guess if its not a problem here, I'll let it go. Next time I'm out in high country, I'm going to bring an extra injection pump with me! Maybe I'll take the tank out and inspect for debris or anything clogging.

By the way, what's with the return hose in the engine bay that goes into the frame rail? Is that just a vent tube from the tank...or what?

[CRSMP5]

gas car goes to can.. diesel just stuck in rail...

mine always soots more in denver...

[wolf_walker]

You could always use this as an excuse to turbo it.

I'm baffled myself.  Isn't the first time, won't be the last.

The missing part stumps me.

[CRSMP5]

actually.. that may be good... need a follow car for smell and tail pipe watching... need to see if unburnt fuel/grey vs soot... smell will tel alot

[vwzzuk]

Yes, that's a great excuse to turbo it. I've been thinking about putting an AAZ in the engine bay too.

Thanks for the help, folks.

[diesel dub]

Had the exact same problem crossing the rockies on rt.80 with my 1.6NA. Couldn't find anything wrong with it. I ended up pulling my cold start advance and it smoothed right out!? Denver wasn't too bad but that's only a mile high. The higher I went the woorse it got! Black soot, missing.  Wyoming was tough on it being it was all over 7000'. Made it a little over 12,000' in rocky Mt. National Park, she hated every foot of it but made it. Ran great thru the heartland. Got home to Pennsylvania and turboed it with a k14. Best decision EVER! Although I don't plan on crossing the Rockies with it again!

[vwzzuk]

Wow, so we had the same problem on the same stretch of highway 80. I'm not crazy after all!

I pulled my cold start cable and it didn't really help much. Perhaps it took the edge off the symptoms a bit.

Puzzled me as it would run great, just like normal, below 7,000 feet or so.