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88 4.2 won't run

5K views 93 replies 8 participants last post by  Tyler980 
#1 ·
I bought an 88 YJ 4.2 straight 6 and I did drive it home... had issues with idle, and no brakes, but the only way I had it running was if it idled at 2k rpms... So, I tried setting timing, and setting idle but when at around 1k it'll just stay there for a few minutes... sputter and die out. So, I then rebuilt the carb, and did a nutter bypass, following the instructions I found on this forum, and I can't get it to start up anymore. Going crazy trying to get this thing going, help? By the way, vacuum lines are all over the place and some are plugged some aren't... I'm very new to working on vehicles.
 
#3 ·
Well, I got it running now... just won't stay running... Theres only one brake not working which is passenger side front... which I realize I said no brakes making it seem like all of them, my bad. The stem/piston, not sure what to call it, in the proportioning distribution block isn't giving any fluid, couldn't find one to replace, so going to replace the whole block one of these days. Thinking about putting in a manual choke at this point as well.
 
#4 ·
Tyler980 said:
Well, I got it running now... just won't stay running... Theres only one brake not working which is passenger side front... which I realize I said no brakes making it seem like all of them, my bad. The stem/piston, not sure what to call it, in the proportioning distribution block isn't giving any fluid, couldn't find one to replace, so going to replace the whole block one of these days. Thinking about putting in a manual choke at this point as well.
Before you convert to a manual choke there is a vaccum valve on the side of the carb that faces the valve cover. There is a small vacuum goes that runs from that to the underside of the carb that faces the firewall. Replace that one line. That should get the choke vaccum diaphragm working. Last week my Yj ran great but would not idle. So I started chasing vaccum lines and replaced that one. Between that and adjusting my idle speed screw so the Yj idles at 800 rpm it now idles great

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#7 ·
Do you or could you get a picture of which hose you're speaking of? Even though I've nuttered I've begun just hooking the hoses back up where they were supposed to be, and so far its gotten a little better for starting purposes... it'll idle till I touch gas, then it'll rev up and bog out.
 
#9 ·
You need to eliminate and/or replace all the vacuum lines now and get it over with once and for all. If they are original equipment, they are worn out. Otherwise you will be chasing around problems with them forever and won't ever be able to get it tuned right.

You can eliminate many of them, since they don't do anything now that you have nuttered it. There are many threads and many opinions on just what else is good to eliminate and what you should keep. It doesn't matter that much, but the ones that are left should be replaced if they look like they might be original equipment.
 
#10 ·
Thanks, I saw the link... Like I've said, I'm pretty new so figuring out what those things are by drawings is pretty difficult for me. If there were a video showing which vacuum lines I need to keep, and which I don't need, would be awesome. Also, I believe its called a vacuum solenoid? Ontop of the engine valve cover, is that still needed after nutter, or no? I've unhooked it and gotten jeep to start, and hooked it up and gotten jeep to start... So I'm unsure. I've tried finding videos of people showing their compartments to attempt to see which hoses they have left.
 
#14 ·
You are going to have to practice reading wiring diagrams and vacuum diagrams so you can get this down. A yj is almost as basic as you can get so learn on this so you are prepared for future work you would like to do.

Here is an overhead of my engine and a shot showing the line for the brake booster. I have 4x4 and distributor in one line and brakes on the other. All the rest has been removed.



 
#18 ·
Tyler980 said:
Alright. Update on jeep. It idles at 800. Can hit throttle and stays running. Kind of sputters and pops. Still stalls when you stop. And thank you for the pictures. Helps a lot.
Have you tried replacing the plugs wires cap and rotor. ? Also sounds like a vacuum leak. I had the same issue until I fixed my vacuum leaks and did a tube up and adjusted the timing
 
#19 ·
Mine came with factory ac so I have a serpentine belt. Everything else is the same, don't be worried about that.

I still say vacuum leak also but you are closer then before. What did you set your timing at now?
 
#20 ·
I set it at 8 BTDC like it said when doing the nutter. The plugs, wires, cap and rotor are all newish. I did find that the vacuum going to the brake booster wasn't plugged anywhere, what would the hose go to? I plugged it for now, but haven't tried driving it, as a hole broke loose in my oil pan, am going to attempt to remove and replace that on tuesday, any advice on that would be awesome as well :)
 
#22 ·
your brake booster line hooks to your intake. that will create a huge vacuum leak if it is not hooked up because you have a huge hole suck air around the carb. it should hook into a large fitting on the intake.

the belts flipping over means you need to check the alignment on your pulleys, if i remember right. i never had that one but i know people do get that trouble.
 
#27 ·
That one that you plugged is where I run my distributor and 4x4 actuator off. You have some hoses coming of the side of the carb, right? Make sure those are plugged, for now. I bet you just have a leak on a vacuum line or a small leak under the adapters under the carb. I had a few leaks in those places and just had to take the carb and adapters off and redo the gaskets and also put rtv between the adapters and the intake and between the two adapters. That finally fixed the little leaks there. Then I had to go buy about 12 feet of non fuel injection fuel line from the local auto parts place and replace my vacuum lines. That finally fixed all the leaks. Your vacuum lines will also go under to a switch on top of you t-case and from there to the actuator on your front axle and firewall. Plus, a vacuum line goes in to behind your dash board. To find out if your trouble is at your intake or at your lines, you can unhook all the little lines and plug the ports and then start the jeep. If it runs a lot better then you know it's somewhere in the distributor/4x4/dash vacuum system and then you just have to go from there.
 
#28 ·
Alright thanks. Yeah there are some small ports on back of carb I need to plug. Do I need to plug the two big ones on too of carb towards the front that use to go down to canister? I plugged it at canister and just took out the big hose that went to those
 
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