performance issue

[81cj]

Last weekend I went wheelin at lake Alpine. Approximately 7500 feet elevation. theres one trail that has some extreme rock crawling areas, lots of large steps and granite bluffs at all angles. Real slow low gear stuff. both times I took this trail my jeep started running bad. Sounded like it was running on 5 or 6 cylinders. If I took my foot off the excelerator it would die. After finally making it through and on the highway it ran fine. I covered about another 100 miles of trails over the weekend that were not as slow and rough as this one and it ran fine. but at the end of the trip we took one last on run on the trail and it did it again. than ran great all the way home. I checked everything float level, fuel filter, fuel pressure, junk in the needle and seat, jets, all electrical connections, cap and rotor, timing, everything is fine. this jeep was original 4 banger that now has a 304. Any ideas ????? vapor lock maybe ???

[jeepsr4ever]

besides elevation what carb are you running?

[81cj]

stock 2b gotta meet ca smog you know

[jeepsr4ever]

[fuzz401]

could be at running slow the air was thin enough to have it running rich at at faster speed it would have more air to it to run better
are you running the return line off the fule filter on it if so I would rule out vapor lock

[FrankNB]

If I remember correctly, some of the MC2150 have to be set for high altitude.. Seems I've read something in my Haynes, I don't really remember.. Have to do with choke or something, or is it that littl leaver with holes in it... anybody know what I'm talking about?

[rollen dean montoya]

i'm not sure if this applies in this case but some jeeps had a wire that
for sea level ops would not be grounded and for high altitudes it should
be hooked up to a ground point. from what my tsm said it suppose to make it run better. just an "W.A.G"(wild assed guess).
later, rollen

[Dusty]

A fellow North Cali jeeper. On Bulltear.


What lift pump are you running? That almost sounds like a possible starvation issue. We have one of ours that for some unknown reason on the trail suffers from that. Ran fine fuel pressure on the flats ect but on the trail it would start to starve. he finally this year went to an electric pump and by passed the mechanical and it ended the babbling engine.

Just a thought. Also what ignition are you running? a DUI might be a consideration?

[Goose]

Two questions come to mind.. This sounds like a rough, slooooow trail at much higher altitude.. maybe the float bouncing around at a steep angle causing it to dump fuel out of the vent into the venturi. I had an edlebrock 1406 that would do that until I put the spring loaded needle and seat in it..