Topic: Hesitation at 45mph

[bluebomber]

New guy here.  I just purchased a 2001 Jeep Wrangler with a 2.5L, automatic.  I had to put a new motor in it but I've had a problem with the Jeep which I don't know if it started before or after the new motor.  When I'm driving along, and it feels like it's going into overdrive, if I don't keep giving the Jeep a little fuel it will start to hesitate or what I would call "bucking".  It's not bad enough to throw me out of the seat.  I also notice some rattle going on towards the bell housing occasionally.  I've completed a full service on the motor including plugs, wires, cap & rotor, TPS, IAC, and MAP sensor.  The motor is still in break-in period so I'm running 15W-40W.  I haven't done anything to the transmission.  A list of my questions:

1.)  Could it be that the torque converter is going bad?
2.)  When the motor went, could it have destroyed the O2 sensor?
3.)  Could it be the Crank sensor?
4.) does this transmission have an overdrive, I'm assuming it does even though the shifter label only has D, 1, 2?
5.) Is it possible to eliminate the overdrive to test?

I've heard that the converter bolts come loose???  Any other suggestions would be appreciated.

[sharpxmen]

New guy here.  I just purchased a 2001 Jeep Wrangler with a 2.5L, automatic.  I had to put a new motor in it but I've had a problem with the Jeep which I don't know if it started before or after the new motor.  When I'm driving along, and it feels like it's going into overdrive, if I don't keep giving the Jeep a little fuel it will start to hesitate or what I would call "bucking".  It's not bad enough to throw me out of the seat.  I also notice some rattle going on towards the bell housing occasionally.  I've completed a full service on the motor including plugs, wires, cap & rotor, TPS, IAC, and MAP sensor.  The motor is still in break-in period so I'm running 15W-40W.  I haven't done anything to the transmission.  A list of my questions:

1.)  Could it be that the torque converter is going bad?
2.)  When the motor went, could it have destroyed the O2 sensor?
3.)  Could it be the Crank sensor?
4.) does this transmission have an overdrive, I'm assuming it does even though the shifter label only has D, 1, 2?
5.) Is it possible to eliminate the overdrive to test?

I've heard that the converter bolts come loose???  Any other suggestions would be appreciated.

1. is it the engine bucking or interrupting or it's like not getting into the next gear and you can see the revs go up?
2. no, and i don't think that what you describe is related to the o2 sensor, but you never know.
3. yes, among other things (i can think of tps, map sensor, dist and rotor, spark plugs/wires/coil)
4. usually you have an o/d button or position on the lever, not familiar with the Jeep auto tranny but there are a few guys here that have one so they might be able to help
5. same as #4

if i understand the behavior correctly from what you describe i think is fuel or spark related, i don't think it's the tranny unless there's somehow something jamming in there to make it hesitate (but in that case i would guess there will be some noise associated with that) - but again i am not familiar with the auto transmission on the Jeep so someone else might have experienced this.

just a thought, i am thinking if you can replicate that with the rear axle on jackstands then you could do more troubleshooting (and in that case would maybe point towards the tranny since the engine won't be under the same load as driving on the street).

[Bounty Hunter]

Your jeep should not have an OD tranny, it's likely a true 3spd.  What you feel may be the torque converter locking and unlocking.

[bluebomber]

The best way I can describe it would be like  a misfire.  I've serviced everything in the ignition system with new parts and it has never gone away.  It always happens when I'm going between 40 and 50 mph.  I'm going to try to pull any codes tonight.

Bounty, do you think then that the converter may be failing??

[sharpxmen]

Your jeep should not have an OD tranny, it's likely a true 3spd.  What you feel may be the torque converter locking and unlocking.

would the revs go up and down when that happens?

[bluebomber]

To be honest, it happens so fast that I don't notice the tach jumping.  It might miss three times, or it might miss several times.  But it always seems to be around 40 to 50 mph.  It happens when the motor is cold or hot.  If I check for codes tonight and don't find any, would a good suggestion be to empty the tranny fluid and put a new filter on?  Do these tranny's have a drain plug on the converter?

[bluebomber]

OK, I scanned the codes and there weren't any present.  I'm thinking about draining the transmission and changing the filter.  I checked the fluid on the dipstick and it looked darker red but didn't have a burnt smell.  But since I've acquired this from someone who apparently didn't take good care of it, it might not be a bad idea anyway.  If the issue gets worse I'll know it either wasn't this or it's a tranny problem.  I'm also going to check the cable while I'm there to make sure it's correctly adjusted to shift down when required.  Sound like a plan?

[dwtaylorpdx]

Might be the gizmo in the distributor, "cam position sensor"

I'm chasing a similar issue that I think I've narrowed down to fuel delivery but I need to pull the tank.


Dave

[Sidscan]

How is your tranny fluid level?  Check for binding on the auto trans cable at the air intake...kinking or sticking may be causing misshifts.

[bluebomber]

Tranny fluid level was fine but I'm going to put a new filter in it this weekend hopefully.  I didn't notice any burnt smell from checking the fluid on the dipstick.  I might be able to get a better sniff once I empty the pan.  I'll check the cable and take it for a test run this week to see if the tach jumps when it happens.

[bluebomber]

Anybody got the torque specs for the tranny pan bolts?

[Dylan]

Anybody got the torque specs for the tranny pan bolts?

13ftlb/17Nm

[bluebomber]

OK, here's the latest saga to my story.  After test driving the Jeep and finding out that the RPMs don't go up when the hesitation happens, I took the Jeep to a buddy's garage because they have a lift and also more tools than I do.  I had a Magnaflow catalytic converter and Borla cat back exhaust system that I had ordered put in and also changed the transmission fluid and filter while it was on the lift.  We checked the fuel pressure and the reading was fine.  I took the Jeep out for a test ride and the the same thing was happening.  Hesitation between 40 and 50, no power going up steep hills.  We disconnected the lock-up solenoid on the transmission and I took it for another run.  It ran great without hesitation.  Figured it was the solenoid not working.  But I noticed something else.  When I'm driving in the lower gears I get a new hesitation.  Sporatic, not always there.  My buddy also noticed that it hesitates at initial throttle.  We checked everything again, fuel pressure, plugs, wires, cap, and rotor, but couldn't find anything.  Sprayed everyting down with water and nothing showed.  He suggested that because it's a new motor that the computer may need re-flashed to take it back to stock.  I'm a little unsure about doing this because that's another $100.00 and I don't even know if that's the problem.  I'm getting agitated because now I don't know if I should be looking at the engine or the drivetrain. 
Should I run the Jeep without the lock-up solenoid plugged in?
Could this hesitation be the transmission slipping?
Should I have the computer re-flashed?
Any suggestions?

[sharpxmen]

OK, here's the latest saga to my story.  After test driving the Jeep and finding out that the RPMs don't go up when the hesitation happens, I took the Jeep to a buddy's garage because they have a lift and also more tools than I do.  I had a Magnaflow catalytic converter and Borla cat back exhaust system that I had ordered put in and also changed the transmission fluid and filter while it was on the lift.  We checked the fuel pressure and the reading was fine.  I took the Jeep out for a test ride and the the same thing was happening.  Hesitation between 40 and 50, no power going up steep hills.  We disconnected the lock-up solenoid on the transmission and I took it for another run.  It ran great without hesitation.  Figured it was the solenoid not working.  But I noticed something else.  When I'm driving in the lower gears I get a new hesitation.  Sporatic, not always there.  My buddy also noticed that it hesitates at initial throttle.  We checked everything again, fuel pressure, plugs, wires, cap, and rotor, but couldn't find anything.  Sprayed everyting down with water and nothing showed.  He suggested that because it's a new motor that the computer may need re-flashed to take it back to stock.  I'm a little unsure about doing this because that's another $100.00 and I don't even know if that's the problem.  I'm getting agitated because now I don't know if I should be looking at the engine or the drivetrain. 
Should I run the Jeep without the lock-up solenoid plugged in?
Could this hesitation be the transmission slipping?
Should I have the computer re-flashed?
Any suggestions?

I don't think is the computer, doesn't make sense to need a flash unless it was flashed with a different code before. can't help you with the auto transmission, i don't even know what the lockup solenoid is - but just thinking, if it was slipping wouldn't the rpm would go up when that happens?

[bluebomber]

I think that's what sharpxmen was trying to determine.  I would think that the RPMs would increase if the transmission was slipping.  Not the case though.  I talked to another guy about chevy auto trans and he said that they had the same problem with the lockup converter hesitating.  He said that the engine had a miss and it was causing the transmissions not to lock up properly.  I'm at a loss here.  I'm not getting any codes to think that it is a misfire.  I've checked or replaced everything I can think of but the Crankshaft sensor.