95 YJ 2.5 5-speed running rough

D

Diablo joe

New Member
Joined
Jul 10, 2024
Messages
12
Location
Derry pa
Started About a week ago driving along and it feels like it's not getting enough fuel lopes sounds like it's missing a cylinder. Runs like crap.

Replaced
Fuel filter
Fuel pump
Plugs
Wires
Cap and roter
Fixed 2 vacuum leaks.
Cleaned out the little ccv fitting on the valve cover.


Ran perfect last night and this morning. Hopped in it after work ran like crap again.

Any ideas or thoughts are greatly appreciated
 
2nd the throttle body cleaning. Sounds like you've been shooting the parts cannon pretty hard on this. But not a bad thing as many of those parts are probably past their prime anyway, right? Here are some non cannon approaches as well. MAF sensor cleaning. Not that familiar with your year and engine config...but I'd borrow fuel pressure gauge (should be schrader valve on fuel rail that feeds injectors) and check that pressure. If your year/engine has fuel pressure regulator, that will help determine if that is OK. Pretty sure it will have one, and prolly only $10-15 part to replace. I'd run a tank or two with quality fuel system cleaner like Tecron, lucas, etc....that will clean up injectors, piston tops, valves, plenum, etc. if not done already. Speaking of injectors (only 4 to deal with) I'd check to make sure they are all squirting/atomizing properly. They can go bad...and sometimes be intermittent failure like you are describing...especially with feeling like starving for fuel. Check the wiring to them as well, the plugs and follow them back a bit...subject to a lot of heat! Lastly, check/clean/re-stablish your primary grounds! Like battery to block, etc (not sure how many on yours) those can get rusty and wonky over 30 years and cause all sorts of probs (usually on/off type probs at first) with how things are running...as it can cause little shorts to ecm, injectors, ignition, etc. Some things to try during a fun saturday...without a ton of money spent. Good luck, let us know.
 
1989YJguy said:
2nd the throttle body cleaning. Sounds like you've been shooting the parts cannon pretty hard on this. But not a bad thing as many of those parts are probably past their prime anyway, right? Here are some non cannon approaches as well. MAF sensor cleaning. Not that familiar with your year and engine config...but I'd borrow fuel pressure gauge (should be schrader valve on fuel rail that feeds injectors) and check that pressure. If your year/engine has fuel pressure regulator, that will help determine if that is OK. Pretty sure it will have one, and prolly only $10-15 part to replace. I'd run a tank or two with quality fuel system cleaner like Tecron, lucas, etc....that will clean up injectors, piston tops, valves, plenum, etc. if not done already. Speaking of injectors (only 4 to deal with) I'd check to make sure they are all squirting/atomizing properly. They can go bad...and sometimes be intermittent failure like you are describing...especially with feeling like starving for fuel. Check the wiring to them as well, the plugs and follow them back a bit...subject to a lot of heat! Lastly, check/clean/re-stablish your primary grounds! Like battery to block, etc (not sure how many on yours) those can get rusty and wonky over 30 years and cause all sorts of probs (usually on/off type probs at first) with how things are running...as it can cause little shorts to ecm, injectors, ignition, etc. Some things to try during a fun saturday...without a ton of money spent. Good luck, let us know.
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Yeah it's what I figured all that stuff in the long didn't hurt to replace so I started there. I wanted to replace the gas tank skid plate anyway so the cleaned up one had been sitting in my garage so I figured perfect time to it. I'm going to borrow a pressure tester this weekend. I checked the injector wiring and most wiring connectors. I grab some cleaner on my way home from work tomorrow and hose out the throttle body.
 
Yeah, and check those grounds! Again, not familiar with your config....I'm assuming fuel rail with 4 injectors, but I know some of the old 2.5 had TBI fuel systems (throttle body injector) but I'm more familiar with traditional carbs and injection systems. If it's a "traditional" throttle body, best to remove completely so you can use cleaner (and if needed rags, nylon tooth brush, etc) to clean both sides of butterfly and body internals. To be honest, your description of problem sounds like injector, fuel pressure, etc issue to me, but no expert. However, I've had very dirty throttle bodies cause some poor running conditions too. I like to test drive after each process...to help determine what cause was. Whenever possible. If you knock out 6 things and things sorted...you end up not know the culprit. For what that's worth.
 
Checked grounds hosed the throttle body out 2 times scrubbed every bit of grease and dirt took tps off and the idle gear off cleaned all that no change
 
Dang...sorry man, you are really having to chase this around. No small projects that you've done so far (especially fuel pump). so kudos for hanging in there.
Couple things...if fuel related, very possibly either injectors (dirty or failing...one could cause serious issues as you mentioned it feels like it running on 3 cylinders at times) or fuel pressure. You know pump is good, you know filter is clear, so time to check that fuel pressure and regulator. If injectors, pressure good, it may be spark related even though it "feels" fuel starved. Google "jeep symptoms of failing coil" and see if the list matches up to your condition. Fairly cheap thing to replace...and since you are new on plugs/cap/rotor/wires this will complete your ignition re-fresh and eliminate that possibility. Usually manifests and poor acceleration, hard starts, bad fuel economy, stalling, etc. You've gotta be getting close :)
 
speaking of coil....I remember reading thread in the past about the notoriously wonky coil connector on the mid 90's 2.5's . And causing running issues. If you fiddle with it a little while it's running you could see if that connector is shorting. When my 89 4.2 was intermittently failing to start/run it was the wires going into the distributor (PO did the "nutter bypass") from the ignition module. Over time/heat and just moving back and forth, one of them broke off going into the plug connector. If it was in just the right position, it would connect enough to start and run. Move a little, and no dice. Was driving me crazy until I found that broken wire.
 
you are on the right TRACK, keep going and you will fixed by the information that other members provide . one the big plus about this issue is that you are keeping members updated, this helps others in future should problem arise. good luck and safe driving.
 
1989YJguy said:
speaking of coil....I remember reading thread in the past about the notoriously wonky coil connector on the mid 90's 2.5's . And causing running issues. If you fiddle with it a little while it's running you could see if that connector is shorting. When my 89 4.2 was intermittently failing to start/run it was the wires going into the distributor (PO did the "nutter bypass") from the ignition module. Over time/heat and just moving back and forth, one of them broke off going into the plug connector. If it was in just the right position, it would connect enough to start and run. Move a little, and no dice. Was driving me crazy until I found that broken wire.
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I saw something about that the other day I wiggled the pigtail around while it was running no change
 
1989YJguy said:
Dang...sorry man, you are really having to chase this around. No small projects that you've done so far (especially fuel pump). so kudos for hanging in there.
Couple things...if fuel related, very possibly either injectors (dirty or failing...one could cause serious issues as you mentioned it feels like it running on 3 cylinders at times) or fuel pressure. You know pump is good, you know filter is clear, so time to check that fuel pressure and regulator. If injectors, pressure good, it may be spark related even though it "feels" fuel starved. Google "jeep symptoms of failing coil" and see if the list matches up to your condition. Fairly cheap thing to replace...and since you are new on plugs/cap/rotor/wires this will complete your ignition re-fresh and eliminate that possibility. Usually manifests and poor acceleration, hard starts, bad fuel economy, stalling, etc. You've gotta be getting close :)
Click to expand...
No worries I'm prone to goofy jeep problems. Had an exact same jeep model 10 years ago would die randomly going down the road couldn't figure it out. Mechanic buddy of mine was helping me out tried everything couldn't figure it out. Just out of luck he leaned on the big wire connector on the firewall and it shut off. Turned out the wire for the fuel pump shut off was broke inside the insulation. So when it heated up it lost connection.

I don't have a pressure gauge handy but I hit the shader valve and shot gas across the yard. I don't think itsxa pressure problem cause it revs fine just seems to be missing a cylinder. I think it's the second one back from the front the plug color was different 3 were all the same brown color it was black.

New injectors are ordered will be here aunday
 
Diablo joe said:
No worries I'm prone to goofy jeep problems. Had an exact same jeep model 10 years ago would die randomly going down the road couldn't figure it out. Mechanic buddy of mine was helping me out tried everything couldn't figure it out. Just out of luck he leaned on the big wire connector on the firewall and it shut off. Turned out the wire for the fuel pump shut off was broke inside the insulation. So when it heated up it lost connection.

I don't have a pressure gauge handy but I hit the shader valve and shot gas across the yard. I don't think itsxa pressure problem cause it revs fine just seems to be missing a cylinder. I think it's the second one back from the front the plug color was different 3 were all the same brown color it was black.

New injectors are ordered will be here aunday
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With it running, spray some water with a squirt bottle on the exhaust manifold right next to each cylinder. The dead one should boil off the water much slower than the others.
 
Alright new injectors in better but still not right. Narrowed it down it's the 3rd cylinder back fron the front. Number 4 in firing order. Trying to round up a compression tester next
 
silly as it may seem, check you plug , it may have got damaged on installed. good luck and save driving .
 
After my rebuild on my YJ, it ran great for a week. Then all of a sudden it felt like it dropped a cylinder or two. Power was greatly reduced and I could hear it had at least a dead cylinder. My issue wound up being in the injector harness. I removed all the injector plugs one by one and made sure they were cleaned out, I then added dielectric grease to all of them (I had meant to do this during the rebuild and forgot) and she's been running great ever since. I think one of them was either a tad loose or dirty and would lose connection to the injector. I swapped to k-suspension 4 hole injectors during the rebuild so I figured they were in good shape being newly rebuilt.

Just a thought of something to look at. You could wiggle your injector harness around at the plugs and see if it picks up the cylinder, then you'd know that is your problem.
 
Plastic Fury said:
After my rebuild on my YJ, it ran great for a week. Then all of a sudden it felt like it dropped a cylinder or two. Power was greatly reduced and I could hear it had at least a dead cylinder. My issue wound up being in the injector harness. I removed all the injector plugs one by one and made sure they were cleaned out, I then added dielectric grease to all of them (I had meant to do this during the rebuild and forgot) and she's been running great ever since. I think one of them was either a tad loose or dirty and would lose connection to the injector. I swapped to k-suspension 4 hole injectors during the rebuild so I figured they were in good shape being newly rebuilt.

Just a thought of something to look at. You could wiggle your injector harness around at the plugs and see if it picks up the cylinder, then you'd know that is your problem.
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I have tried wiggling every wire I can get my paws on nothing seems to change it.
 
Ok did compression test 130 135 range on all cylinders. So that's good to a point that the motor hasn't chewed its own guts out. I know they aren't great numbers but they are consistent. Positive update had to put it all back together figured good time to start retrouble shooting so flipped spark plugs from 1 and 3 cylinders and 1 is dead now. So I'm going to the part store in a bit and hopefully a new plug will fix it. I feel dumb as hell if that's what it is .
 
you done a" GOOD JOB", dont feel bad about the plug, it has happen to many of us. the point is that you and many member learn alot from your work, because you keep us up informed. good luck and safe driving.
 
Diablo joe said:
Stupid brand new plug. Purring like a kitten now granted it's a 29 year old half blind in one eye, slightly dementia ridden, with a limp kitten but purring all the same
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Glad you got it figured out. I know it's annoying when it's something simple but at least it was something simple and you worked it out.
 
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