Possible carb vacuum leak

The odometer is at 96k. Which i believe is correct from the way the interior and rust looks. The previous owner had the transmission and engine rebuilt at a shop. So i'm not sure if the original engine was rebuilt or if another rebuild one was put in.
 
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cameron.rw said:
So here is the story on my weber 32/36 for my 4.2. When I got it I could tell a slight sputter in performance at low speeds. I could hear an almost hissing sound when putting it into Drive and Reverse. In park and neutral I really didn't hear much. So I decided to make sure the Idle and mixture screw where in the correct place. I was noticing the Mixture wasn't really making any affect at the two turns out. Only when it was turned in completely was I able to to really feel the engine to run rougher. I then just put the idle and mixture screw in the recommended position. (1.5 turns and 2 turns).

Today I went back to jeep and it was basically refusing to start. I noticed I left the choke on all night (this weber has the manual choke) but I do not think that would cause this. I can get it to start and run as good as I did before by putting the idle screw all the way turned in. Now the mixture screw has basically zero affect. But it did not do much before this.

I am thinking this is a vacuum leak because of the hiss I can here when I put it in drive.

I am a beginner so I am not really sure how to start here.
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Cameron
You may have a vacuum leak at the brake booster. You can remove the hose to the brake booster and plug It temporary. If you drive with the hose disconnected you will have little or no brakes. You said the engine will run with the idle speed screw turned in all the way. With the idle screw turned all the way in, the mixture screw will have little or no effect on how the engine runs. This is because with the idle turned up high, the carb is no longer running on the idle circuit.

You could also have a leak at the base of the carburetor wher it connects to the manifold. Check the carb mounting nuts. Are they tight? Once you find your problem, set the mixture screw back to the recommended turns out. Then set the idle screw so the rpms are about 700. Then go back and set the mixture for the smoothest idle. Good luck
 
Where would I find the correct settings for the idle and mixture screw? I was seeing 1.5 turns for idle and 2 for mixture screw. Those weren't specifically for the 4.2 and the installation manual has even more vague instructions.
 
Try the 1.5 turns out on the mixture screw. The idle screw is two turns in after the idle screw contacts the stop. These settings will only work if you fix the vacuum leak.
 
I haven’t worked on the Jeep for awhile but I wanted to send this picture of one of the plugs. This is to me is the worst one of them all. I’m assuming this is oil and isn’t a good sign of the engine. One or two other plugs had the white ashy build up which if my research is right is also oil. But If I remember right 3-4 of the plugs just had the carbon build up like the one I sent before. I’m planing on replacing the plugs and using seafoam. I did put in high miliage oil so I’d hope that would help. I’m thinking this could be a serious issue but I’m just going off of what I’m reading online so I really don’t know. Thanks for the help!

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I was confused on why this one was like that and the others weren’t. The engine was low on oil so maybe the engine is burning oil but I don’t know how to tell for sure. I already cleaned the plugs and I’m going to put new plugs in as I said before. The plug looked like the examples of oil fouled plugs but ive never experienced one I knew was burning oil for sure. The people I got the Jeep from had the engine rebuilt by a shop 3 years ago and I’m seeing the shop has mixed reviews so I’m hoping they didn’t do anything majorly wrong. Maybe they just had the mixture too rich but again I’m an amateur here so I’m going off of what problems I can identify.
 
Unfortunately I'm not sure anyone can give you a straight answer as to what's causing this problem. That engine often goes 200,000 miles so why it was rebuilt early and why it has this problem means something wasn't done right. It could be bad valve guides or a crack in the head that wasn't caught, 100 different things.

When you put new plugs in drive it for 100 miles and check them to see if it's one cylinder or all cylinders. I've seen PCV valves fail and suck a quart of oil into the engine.

You may want to call the shop and see if they have any records of what they did to the engine. Full overhaul or top end only? What a previous owner says and what actually happened is usually different.
 
Yeah I will certainly be checking up on the plugs and oil when I get the time to put miles on it. I’ll call the shop up and ask about the repairs. When I get more info or find something else I’ll report back. Thanks for the help so far!
 
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