9o YJ not running well

90YJoe · #1 (**permalink**) 06-18-2008, 01:33 AM

I have a 90 YJ w/ TBI 2.5L and recently have had a problem where it runs ok when it's cold, but when it reaches opperating temp. it suddenly starts runnig rough, and bogs out when trying to throttle up. I put a new ECM in it and that seemed to help slightly, but still does it. I also smell fuel from the exaust when I stop the engine. I just bought this used recently and am working the bugs out.

Bounty__Hunter · #2 (**permalink**) 06-18-2008, 09:32 AM

I had a YJ with a clogged catalytic converter, once the exhaust would heat up, the catalyst would expand and choke off the engine. it would run worse the longer it ran.

Jeepsburg · #3 (**permalink**) 06-18-2008, 11:38 AM

Quote:

Originally Posted by 90YJoe

I have a 90 YJ w/ TBI 2.5L and recently have had a problem where it runs ok when it's cold, but when it reaches operating temp. it suddenly starts running rough, and bogs out when trying to throttle up. I put a new ECM in it and that seemed to help slightly, but still does it. I also smell fuel from the exhaust when I stop the engine. I just bought this used recently and am working the bugs out.

I am having the same exact problem with my 89 yj with a 4.2L inline 6.
I put it in the shop at my vo-tech for a month, and...

I went to drive it home and as soon as it heated up to normal operating temp, it started running around 600 or 500 (hundred) rpms. it was really low and you basically could not drive it. I was able to drive it back to the shop after it cooled down, because it did not heat back up until I was back at the shop.
I replaced the distributor, and I believe that fixed that problem, but it still would bog a little when you would step on it hard. So I replaced the Ignition Control Module (same thing as ECM?) with another I ICM from a junk yard which also seemed like it helped, although I think it might be going too(because the heat makes them go). The mech at my school cleaned out the carb, but did not use a rebuild kit (he tried to reuse a bunch of seals and such) so I think that it did not get done the right way.
I just gave my jeep a tune up (placed spark plugs, wires, and fuel filter) still does not run the right way. Also the spark plugs looked as though they were runn a little lean, but since I'm not a mech. I was going to take my plugs to a mech and have him look at them. So I think that the problem is still the carb., but because it only does it when it's hot it might also be my ICM from the junk yard.

Hope that helps you out. Please let me know if you have any questions, because I'm trying to fix my Jeep and I might be able to help you out more. Also if you figure it out, PLEASE let me know.

Thanks, Jon.

P.S. - Does TBI = Throttle Body Injection? If not what does it stand for, and is your YJ a carb? I also get a lot of fumes up in the cab.

90YJoe · #4 (**permalink**) 06-18-2008, 11:17 PM

Yes TBI=throtle body injection. I have wondered if timing had a factor in my problem so I put a timing light on my engine after it was warm and stumbling. It seemed to be alright. It was bouncing around a little but that was to be expected as rough as it was idling. Have you checked for vacume leaks? Another possibility is the coil?

90YJoe · #5 (**permalink**) 06-18-2008, 11:20 PM

Sorry, the catalytic converter is not an option. It doesn't have one. It must have been removed before I got it. Thanks anyway!!

Jeepsburg · #6 (**permalink**) 06-19-2008, 05:55 PM

Quote:

Originally Posted by 90YJoe

Have you checked for vacuum leaks? Another possibility is the coil?

I have heard I should check for vaccum leaks, (but I don't think its that cause right now it only sputters when it hits a bump), so no, I have not checked for vacuum leaks, but I think I'm going to take my Jeep to a friend mech. around my place on Tuesday (18354, PA).

The mech at my school replaced my coil with another from another vehicle and it was giving him the same problems. Also I just did a tune up on my car, with nothing different afterwards (plugs, wires, and fuel filter). If I do take it to the shop, then I will let you know what was wrong with it if it gets fixed.
Jon.

pitbulld45 · #7 (**permalink**) 06-19-2008, 09:34 PM

Since the trouble is when it warms up it could be the pick up coil in your distributor.

ThorBuilt1 · #8 (**permalink**) 07-23-2008, 01:47 AM

Hey,
I have an 88 and has similar problems...starts great cold but when comming up to lights i have to stay on the peddle or it dies...and it wont start if its warm..i have to pour gas down the tbi...i spoke with a jeep mechanic today and he told me to replace the coolant sensor...i guess when that goes bad it dumps fuel in her and will make it act that way...hence the gas smell...

ThorBuilt1 · #9 (**permalink**) 07-23-2008, 01:48 AM

coolant temp sensor