ZJ stall downhill

[JackstandJohnny]

i've had this problem before, on a different jeep, now have it again,

going down hill the jeep wants to run at a very low idle and/or stall out. this weekend rpms would drop down to 250rpm when i'm going downhill, and last week, was stalling out completely.  i've replaced the NGK sparkplugs with champion ones as per spec (the ngks were shot) and i pulled the Air Idle controller too. it was really dirty.  but still, the low idle is kinda sucks.

i could fix said problem by installing 4.56 gears............ but wondering where to start? no codes either.  thinking AIC motor/sensor might just be screwed.


any suggestions?

[WhiteOut]

I'll bring my spare IAC over this weekend.

[cLAY]

I've had ZJs where the fuel picktube wasn't all the way to the bottom of the tank. This manifested as the engine bogging when doing a fast sharp left turn. Pump is offset to the drivers side and the fuel would slosh to the right side and the pump would run dry. On my dads Jeep you couldn't let it go much below 1/4 or it would stall on even a gentle left turn. On my 5.9er if it goes much below 1/8th it boggs on a hard left.

Maybe similar? Ever had the tank real low? Near 1/8th?

[JackstandJohnny]

hmm, i have read that too clay,  the times its done it were at least half a tank.  and its only at idle; ive not had an issue on the gas.  just a weird jeep thing?

[Immortal]

couldn't let it go much below 1/4 or it would stall on even a gentle left turn.

This used to happen on my 99 XJ. I pulled the fuel pump, checked it out (no problems apparent), put it back together.... hasn't happened since. It never bogged down, it would just cut out.
 Weird.

[JackstandJohnny]

hey clay i've never had it really below 1/8" of a tank, and it definitley wasn't stalling out around left hand corners. its weird because it doesn't feel like its struggling, or misfiring at all, just gets really low then dies a 250 rpm. but if i let off the brakes and let the engine do its thing the rpms will increase like they should...
 but i do think its a fuel problem.  new plugs, cleaned the AIC motor, and it runs just fine.  just those real steep downhills where i'm on the brakes as well. (think coming down top of the world towards Fish East, thats where i noticed it) 

so i'm going to replace the fuel filter, its probably factory original anyways, and clean out the fuel pickup.  might just be gunked up or something, might just pull it and investigate!

thanks for the ideas guys.

[cLAY]

Another thought. Have you relocated the charcoal canister? Is it hooked up correctly? I tired to plug mine off before I relocated it and had vapor lock problems.

If you are going to pull the pump I recommended cutting an access hole in the floor to get to it. While its not a big job to drop the tank when at home its nice option to have if you ever need to get at it while on the trial. I think I found some measurements on NAXJA on where to cut. Afterwards I cut out a piece of sheet-metal about 1" larger on all sides and screwed/siliconed it down to cover the hole.

BTW 4.0 or 5.2L?

[JackstandJohnny]

Another thought. Have you relocated the charcoal canister? Is it hooked up correctly? I tired to plug mine off before I relocated it and had vapor lock problems.

If you are going to pull the pump I recommended cutting an access hole in the floor to get to it. While its not a big job to drop the tank when at home its nice option to have if you ever need to get at it while on the trial. I think I found some measurements on NAXJA on where to cut. Afterwards I cut out a piece of sheet-metal about 1" larger on all sides and screwed/siliconed it down to cover the hole.

BTW 4.0 or 5.2L?

5.2. and yep, i relocated the charcoal canister under the hood.  95% sure its hooked up correctly. the connections fit anyway lol. 

i kind of like the access panel idea too

[esi]

shot in the dark but, maybe your brake booster has something to do with it. Idling and on the brakes, not that it shouldn't do the same sitting still with a foot on the brakes.

Fuel pump access hole in the back is a great idea as well, I did it to one of mine. Lift unhook wires and fuel line, blow gravel and dirt out of the way, turn big threaded lock, and fuel pump is out in about 5 min.

If you need Z scraps I have a parts one in the back forty as well.