Had a similar problem. I replaced the fuel filter first that didn't fix it. So then I changed my spark plugs, plug wires, distributor cap, and coil and it runs great now. So since you've done the filter and plug and wires, I would just get the coil and see if that works.

 

I've got a new-to-me Jeep as well. I cleaned the throttle body today and blasted out what was likely 16yrs of crud. A throttle body gasket is only a couple of bucks. A good dousing with throttle body cleaner and a light brushing got it looking like new inside.

It can't hurt and it might make a world of difference.

 

runs rough after heating up

I have a similar problem. I replaced the cap and rotor along with ngk plugs and new wires. The 4 cylinder runs great when it is cold but after it warms up to normal temp it starts to idle rough. Does not die but drops down to about 600 rpm. If the idle is increased it seems better. When it is cold the idle is higher and runs smooth. Runs great under a load or driving hard through the gears. Is there some sort of valve that changes when the engine warms up? Should I just increase the idle so when the engine is warm it is closer to 1000 rpm? What is the normal rpm for a 1995 4 cylinder wrangler?

 

thanks mrob - i was taking aim at the distributor next. either a new cap or just get a whole new dist.

 

I ran double platinums plug and mine ran pretty bad. I drop in some champion copper plugs instead and it ran much better. You could try that it pretty cheap idea. Maybe 10 bucks.

 

Here is a small update after driving it to work today (crossing my fingers not to break down). I noticed the (I think oil pressure) gauge jumping around. It seems to jump up to 80 and max out there for a while and then it will drop back down to 40 randomly and keep doing that.

Also when I am shifting through the gears at higher (2500 or so) RPMS I see a yellow light on the dash which is in the shape of a house! After I shift into the next gear the light will go out and sometimes come back on when the rpms get back up a bit in the next gear.

 

Here is a small update after driving it to work today (crossing my fingers not to break down). I noticed the (I think oil pressure) gauge jumping around. It seems to jump up to 80 and max out there for a while and then it will drop back down to 40 randomly and keep doing that.

Also when I am shifting through the gears at higher (2500 or so) RPMS I see a yellow light on the dash which is in the shape of a house! After I shift into the next gear the light will go out and sometimes come back on when the rpms get back up a bit in the next gear.

Normal oil pressure on my 4.0 is a little over 40psi while running down the road. It does drop off when the RPMs drop. I think that house light may be your shift indicator. Supposedly tells you when to shift... I have one but I ignore it and shift when the sound of the engine tells me to.

Your plugs could be the problem - Jeeps don't like special plugs. Look at this thread: Questions about Spark Plugs - JeepForum.com

Is your Jeep fuel injected? If so have you tested the fuel pressure?

 

Not exactly sure what the normal pressure should be. Here is a crappy pic I snapped of the gauge while it was going on:

 

Well it was having this issue before I changed the plugs. That was one of my main purposes of changing them. I have a new dist cap and rotor and also a new starter on the way (I know the started has nothing to do with this particular problem). As for fuel injected I doubt that it is but can't be 100% sure. It is a 1992 4 banger. I do know that the exhaust sounds like crap. Rattly raspy sounding. Did not see any obvious exhaust leaks when I was underneath it.

She sure is a good looking jeep though:

 

Do you have a Cat.? Sometimes the honeycomb breaks up and when you hit the gas the broken parts get pinned against the back and block the flow of exhaust gases, the muffler can cause it too.

 

I am kind of leaning towards o2 sensor after doing some research after I replace the dist cap and rotor. The symptoms add up, however I do not have a check engine light on which is the normal for a bad o2 sensor..

 

Well it was having this issue before I changed the plugs. That was one of my main purposes of changing them. I have a new dist cap and rotor and also a new starter on the way (I know the started has nothing to do with this particular problem). As for fuel injected I doubt that it is but can't be 100% sure. It is a 1992 4 banger. I do know that the exhaust sounds like crap. Rattly raspy sounding. Did not see any obvious exhaust leaks when I was underneath it.

She sure is a good looking jeep though:

According to the Chiltons manual (which you really ought to get a copy of) you have MFI (multipoint fuel injection).

I wouldn't replace anything else until you get those plugs changed. Sure it was doing it before you changed the plugs, but putting the wrong plugs in is just as bad as putting the bad ones back in. Replacing worn plugs with the wrong plugs ain't gonna fix a plug problem.

 

Well o2 sensor was a no go. I was wrong this is a 1992 model MFI fuel injected as stated above. As far as the spark plugs I was reading and autolite double platinum was recommended that is why I.went with those. If the new cap and rotor don't fix it I am at a loss...

 

that light that looks like a house....its actually an arrow, its telling you to shift up a gear, it lights up at around 2100 rpm in my 93.....its there telling you when to shift for better gas mileage and to start driving like a grandma...

as far as the oil pressure goes...thats a lil high, mines never maxed out, it stays around 60 when i'm driving and 25-30 at idle.


also another thing i didn't notice anyone say, check the actual engine grounds to the frame, and the ground from the frame to the battery, these can corrode over time and you won't get as good of a spark due to this, it can also cause electronics in the vehicle to not work right as the alternator is grounded to the engine(which is grounded to the frame and battery)....might get a good charge, but it can fluctuate your volts as your driving...and not enough to notice on the gauge either, but enough to mess with the computers

 

I will add that is also seems to happen when I go over bumpy roads / speed bumps etc.

 

I will add that is also seems to happen when I go over bumpy roads / speed bumps etc.

sounding more and more like a loose/bad ground...i'd really look into that

 

I wi try to look at the ground on it today

 

thanks mrob - i was taking aim at the distributor next. either a new cap or just get a whole new dist.

No prob man.. I would also replace the coil if the distributor cap and rotor don't work.

 

My jeep was doing the same thing. Turned out to be the o2 sensor. Now it runs great.

 

Also my exhaust sounds like shit. It sounds almost like it would with an exhaust leak but I see no visible hole. However I can go underneath it and and grab the muffler and wiggle it around and it sounds and looks loose. Wonder of that has anything to do with it.

I tried to replace the gps sensor last night but the one I bought from oreillys crumbled in my hand while trying to install it. I couldn't even believe it. It was a bwd brand.

 

Update - I have replaced pretty much everything I can replace ignition-wise. The other day we replaced the ignition coil and put a new starter in it (starter was intermittently catching and needed replaced...Unrelated to the problem at hand). Every little thing I am doing is helping a bit but the problem still exists. Once I get the jeep running and warmed up for about 5-10 minutes it runs like a champ...no hesitation at all.

When I go out to start it from cold start it just tries to turn over but won't actually start unless I try for a while. Really leaning towards a fuel problem now. I need the tool to check my fuel pressure which I hear should be between 31-39 PSI. It's like once the fuel gets through the system it runs fine but from a cold start the fuel has subsided and it will not start at first. When I finally get it started the hesitation goes on for a few miles and after that it is gone. I am pushing towards fuel pump now but will have to check the fuel pressure first.

 

Next target tomorrow will be fuel pressure regulator. Fuell pressure test shows some lower than normal PSI.

 

Figure id post this since a lot of these posts never have resolutions by the person having the problem and does no good to others....

Mine is fixed! (for now) ...the bad thing is I actually can't say what the root cause was. I'll note that I replaced the following:

Fuel filter
Oil filter and oil
Distributor cap and rotor
Plugs and wires
O2 sensor
Ran seafoam through the tank
Tested fuel pressure and it was a steady 35 or so psi.

Here's the story...my dad is a mechanic at American Airlines and has been helping me the past couple of days try to diagnose the problem (explaining to me how everything works in detail which I still don't FULLY understand lol). He came over today to test the fuel regulator and while trying to start the jeep to test it, it would not start at all. Just tried to start but no turnover. We checked the spark again:

Hooked a spare plug to a wire and grounded it to the frame (anywhere metal) try to start it and watch for spark.

We seen no spark..which is odd because I drove it to the store yesterday while it was still having hesitation / dying issues (i died on the way to the store).

We were about to call it quits for the day when he wiggled the wires around the distributor (plug / ignition wires and actual plugs that plug into those components) and made sure they were fully secure. Went to start it and it fired right up first try from cold start and went for a.drive and it drives perfectly. Maybe a short somewhere but if it was it's around the distributor somewhere. Still going strong. I'm happy!

 

Sounds a lot like what mine was doing, every once in a while it ran fine, usually I would get stalling problems and hard starts. Changed out the ICM and it runs great now.

 

Actually we were fishing around for that thing also but weren't sure where to look. Where is it located at on the YJ 2.5L?

 

I have a 4.2 and it was under the washer bottle and radiator overflow on the drivers fender

 

Pull the codes and see what you get. I'm having a similar issue (With heavy bogging nearly to a stall and sometimes even stalling out and having to restart the car) and I got the codes and it was - 12 (ignore, means your battery has been unplugged in the last 50 years, haha), 33 (A/C issue... I have no A/C so yeah, duh, the relay is missing), 24 (TPS! Could be causing your issue as well), 17 (my thermostat is shot), 51 (o2 sensor! Could also be a cause for your problem), and lastly I got 41 (alternator field control circuit opened or shortened) [confused by the last one as the alternator charges up my battery just fine and all]. Good luck. I'll keep checking back here for ideas as to what may be happening with mine. I'm about to go check the grounds as people recommended here for you to try. Hope this helps.

 

Welcome to the Forum BMW1905,

The post you're responding to is from July 2011. It's always a good idea to check the date of the post.
I agree that what that poster sees is the upshift symbol.

Good Luck, L.M.