jeepjeepgirl

Hey guys I'm new to the forum I've got a 89 yj 4.2 litre automatic.

When I start it, it struggles to start then when it finally does it idles around 1500 rpm ok but when i disengage the choke it drops down to around 900 rpm and within seconds it starts to misfire and sputter and eventually stalls. It does this until the engine is warm then runs fine.

I recently changed the oil, replaced the plugs, and air filter. It has the stock carb and as far as i know no nutter bypass or anything like that. It has to pass safety and emissions so I don't want to nutter it yet.

I pulled the plugs and cylinder 5 was completely fouled and smelled of fuel.

Any advice or help would be appreciated.

Thanks

Captain Avalanche

Sure sounds like the carb to me. The choke is not responding properly and the idle setting won't hold the running engine until it warms.

james.mc

I'd swap the plugs around and note where the (seemingly duff) one from cylinder No 5 goes. Run the engine and check the plugs again. It's not unheard of for new plugs to break down as they get hot. If the problem stays with No 5 cylinder (still smells of fuel and wet) then the plug is OK and you have another problem. If the problem swaps to another cylinder with the plug that was in cylinder No5 then the plug is duff and needs replacing.
Next.
Distributor Cap: Check inside for tracking. How old is the distributor cap? How old are the HT leads. If the whole lot is old try a new cap, rotor arm and HT leads.
That should sort out misfire and improve general running.

If it doesn't, then start looking at other potential issues such as the carb, vacuum lines etc. Even a compression check wouldn't hurt but check the cheap/easy/simple things first.

jeepjeepgirl

hey ya thanks great help. The distributor cap comes loose every now and then and it has some troubling starting because i need a new choke but now that I know what it is I can fix it. running into some other problems too with some rear frame rot and such though that I don't know how to fix. thanks.

jeepjeepgirl

its also as if it chokes itself out when I accelerate and then it dies. I don't know what the problem there is.

james.mc

Other than the fact that you may have a specific problem affecting one cylinder....

Ignition Timing: Have it checked.
Using a timing strobe it should be 9 degree BTDC at 1600rpm (if I remember correctly). It's a cheap thing to check before you start looking at replacing things.
I acquired my Jeep (1989 YJ 4.2 i6) not too long back and finally got around to checking the timing. On checking I discovered the distributor body was slack. The timing was 25 degrees BTDC! I was amazed it started at all! Adjusted it to 9 degrees BTDC. Now it starts more easily and ticks over/pulls better at low revs. The timing strobe is cheap to buy.

Carburettor: blocked idle tubes?
Make sure that the idle tubes are not blocked on the carb. Block idle tubes will cause similar bad running symptoms at low revs. For an excellent article on this please read: Easy Fix for Jeep 258 Carter BBD Idle Problem
It's a relatively easy quick check/fix that might resolve rough tick-over.

Vacuum system: cracked split hoses?
Another (cheap/easy option) to check is the vacuum hoses that run all over the engine on our YJ's. They are the thin black rubber hoses you'll see going in all directions. If they are split, your engine vacuum system may be in bad shape and will also effect the way the engine runs. Replace any cracked or split hoses.

jeepjeepgirl

I took it into a shop closer to when I first got it and the guy adjusted the timing from 8 degrees to 4.
As for the blocked idle tubes, I believe that they're clear and clean but I don't feel to confident to remove them and check as it is an old motor and I'm afraid I wouldn't be able to put it back together or something would break.
Also all the vacuum hoses appear to be uncracked and in good condition.
Thanks for your help.

james.mc

Hey! No worries. Good luck! :

james.mc

Just picked up on what you wrote above. I'm reasonably sure the correct (stock) ignition timing advance is 9 degrees Before Top Dead Centre (BTDC) with the engine running at 1600 rpm. It should be checked with the engine running, hence the need for a strobe type timing light.
Timing may be different when an auto gearbox is fitted, that's unlikely but worth checking up on. A few degrees won't make a massive difference but your unit might be 5 degrees out now and it's always good to work from stock settings when trying to fault find.

I'm away from home (and will be for some weeks) so don't have access to the factory issued workshop manual I usually refer to. It would be nice if someone could confirm what I am suggesting on the timing front.

You should have those idle tubes checked by someone though. If they are blocked (or partially blocked) that will cause the rough running symptoms you have.

five points

Im alittle in the same boat, idling problem. the article on cleaning the idle tubes is very easy to follow and do. First time I did it it cured the problem. I thought great, only to have it not idle after a day.

I put a new fuel filtre in and did it again. This worked for a nother day or so. It says in the article that the tubes can be drilled out bigger. any one had this done?

Both times I did it the tube or tubes were plugged.

By the way all the searching on line about this it seems the 89's come up the most with issues.