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Discussion Starter · #1 ·
I'm having trouble keeping the jeep running once it gets hot. It idles fine when cold, but once it warms up, if I try to let it idle, it will die. I have to hold a little bit of pressure on the throttle at stop lights to keep it running. The original owner has disconnected about every single vacuum line, and I don't know what should go where, or if that even has anything to do with it?

'89 YJ with 5 speed manual

I have a ton more problems and questions, but I'm trying not to spam the board.
 

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Find a post by Got it at last. In his signature there's a free link to several Factory Service manuals and a couple Factory Parts Manuals.
Open that link and click on the manual that you need.

It'd help if we knew what engine you have. A 6 cyl has a carb (or had one from the factory) and a 4 cyl engine is fuel injected.

Good Luck, L.M.
 

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'89 YJ 4.2 with MC-2150 Carb & HEI, 2-1/2" Ex. AX-15, NP231 SYE, Adams shafts, F&R ARB, 3
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What type of carb are you running, and are you still using the computer, or has the nutter bypass, or HEI swap been done?
 

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'89 YJ 4.2 with MC-2150 Carb & HEI, 2-1/2" Ex. AX-15, NP231 SYE, Adams shafts, F&R ARB, 3
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I personally went HEI and motorcraft carb and haven't looked back, Not that I'm suggesting the swap would cure your issue, But losing all the electrical and vacuum out of the equation really helps me keep mine running worry free. My biggest complaint is having to adjust the choke preload a tad twice a year when the weather changes from hot to cold. It actually works out for me though, I change plugs, oil, and adjust the choke all at the same time, whether it needs it or not. The weather lets me know when. The choke needs to open up a little sooner in the summer, later in the winter.

As for your issue, Not really sure if anybody still knows how to dial in the stock stepper carb with all your vacuum switches etc unplugged. If you haven't changed your plugs lately You may want to try that first, a cheap and easy way to better your combustion. These old 4.2's really prefer the cheapest copper core plugs you can get, Champion 82's or Autolite 985's. Anytime I play with timing or fuel mixture I start with a fresh set of plugs 1st.

Good luck,
 

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Check this out.

Easy Fix for Jeep 258 Carter BBD Idle Problem

Good info about the stock Carter BBD carb. It might help with your idle issue.

Got it at last went a slightly different rout than I did. He used a MC2150 carb and I went with a re-manufactured non-stepper Carter. The re-man Carter was cheaper than an import Motocraft carb with the adapter and air cleaner.
We both agree, a HEI is the way to go with cheap copper core plugs.
Gap the plugs to .045 and 10* to 12* timing. I like to use a timing light and a vacuum gauge to adjust the timing. A vacuum gauge is essential to accurately adjust the carb

I haven't had to fiddle with a tune up in two years and 10K miles. I'll do new plugs, set the carb and adjust the timing this fall as part of my bi-annual service. I don't think it really needs it, but it's good to take a look at the plugs and adjust the carb & timing for winter.

Good Luck, L.M.
 

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Discussion Starter · #8 ·
Which HEI did you guys go with? I keep seeing things about the advance curves not being right or steel gears eating the cam etc.
 

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I heard the same thing about the HEI gears eating the cam gear.
I bought my HEI through Summit Racing. There were cheaper HEIs online, but Summit Racing is a real place with online help. I contacted Summit and their tech stated that they hadn't had any complaints with their distributors. That was 4 years and about 20K miles ago. So far, so good.

As far as the advance curves not being right, I had some back firing while shifting and some run on (dieseling) at shut down. Both went away when I moved the distributor vacuum hose from ported vacuum to manifold vacuum. YMMV

Good Luck, L.M.
 
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'89 YJ 4.2 with MC-2150 Carb & HEI, 2-1/2" Ex. AX-15, NP231 SYE, Adams shafts, F&R ARB, 3
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X2 Above, went with Summit, excellent tech service over the phone during installation process. Oh Yeah, It came with instructions in English that made sense. LOL
 

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Discussion Starter · #11 ·
Pretty sure I got it fixed. It ran fine tonight, but we'll have to see in the long run. It was the idle fuel pickup tubes. Both of them were completely filled with dirt.
 

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Discussion Starter · #12 ·
Just an update. The jeep ran okay for one small trip, then when right back to it's stalling ways. It was also not running well when I would really get into the throttle, so I broke down and ordered a replacement carb from National Carburetor. I got a refurbished Carter, but I ordered the one for an '87 to avoid some of the electrical connections. It bolted right up in about 15 minutes. I did have to adjust the idle screws slightly, but it runs better and cranks easier than it ever has.
 

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'89 YJ 4.2 with MC-2150 Carb & HEI, 2-1/2" Ex. AX-15, NP231 SYE, Adams shafts, F&R ARB, 3
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Start reading up on the Nutter bypass if your not ready to go with the HEI, it will "bypass" a whole bunch of potential hiccups with your timing and vacuum for you.
 

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Discussion Starter · #14 ·
It already has an HEI. I swapped that first. I was going to wait and go with Fuel injection, but I had to get a new transmission, so I decided to try the replacement carb first. If it continues to run this well, I see no reason for the fuel injection now.
 

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'89 YJ 4.2 with MC-2150 Carb & HEI, 2-1/2" Ex. AX-15, NP231 SYE, Adams shafts, F&R ARB, 3
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