View Full Version : DESPERATE! PLEASE HELP! Engine/Tranny hiccups on Interstate?

September 27th, 2017, 15:23
This is sort of a re-post of the same problem I have been having for some time.
'00 XJ Sport, 4.0, AW4 tranny. Stock except for OME lift.

I commute, at 80mph, 36 miles nonstop, each way daily. Recently the jeep has been "hiccupping" for lack of a better term. It stops pulling for just a second. The cruise control is usually on, but it does it under foot-throttle as well.
It does it more when it is hot outside. In the mornings....maybe once. In the afternoon about 6 times in 36 miles.

I noticed today that during one of the "hiccups" the RPMs jumped up, like pushing in a clutch with cruise control in a manual tranny. So the engine seemed to be revving up as if it lost connection to the tranny. But only for a split second.

Yesterday afternoon it "hiccupped" and it lost all power. It just started slowing down, under no power at all. I tapped the brake to disengage the cruise and gave it gas. The engine revved up and the jeep started pulling again. It felt as if it would just keep not pulling until it stopped....but as soon as I gave it gas all was well.

What in the world is going on? I have heard Crank sensor (new, Napa/Oreilly junk), TPS (replaced, junk yard), Cam position sensor (new/Mopar), and transmission.

If ANYONE has any idea what is going on, please provide some level of detailed response, other than "it's probably your _________." I certainly appreciate the help, but a list of "It's probably your _________" with no other information is not really that helpful. I am not being rude...but desperate. I REALLY need to get this sorted out before I end up stranded on the side of I-40. Is it my TPS, and if so, what would be the symptom and how do you know? If it is my tranny, what is the symptom, what failed, and how do you know? If it is the ______________, what is the symptom and how do you know?

If I "should probably replace my ____________" please offer why and/or how/why you suggest this.

I am good at working on my jeep. I also have a good mechanic. But the XJ is not throwing ANY codes. And you have to drive it hot, at 80mph, for 20 miles or more to make it act up. And it only hiccups a couple of times. My mechanic would be able to agree that it hiccups. But without it doing this A LOT more often or throwing codes, he would not have any more idea of what is wrong than I do.

I really need help with this one. Anyone? Please?

Green Mesa XJ
September 27th, 2017, 16:16
Sounds like the torque converter lockup might be disengaging.

In the 91-95 XJ the torque converter lock up responds to three inputs, TPS, brake switch and I think it was the transmission computer .

Our early 90s XJ did something like this once when the inlaws borrowed it so I didnít experience it first hand. They said it felt like it had no power, no one thing seemed to make it better or worse, like taking it out of gear and putting it back, cruise control vs peddle control.
I replaced the brake switch, and the TPS, never happened again. Other thing was it had gone through one hell of a rain storm and the windshield had a leak so may be in our case water was involved.

Oh I also drain the transmission and replaced it with the recommended fluid, I donít think that was an issue .

September 27th, 2017, 16:25
Thank you for your detailed response and experience. It is useful. I will see what other things get posted and try to sort through it.

I was actually thinking torque converter myself. But I read that the symptoms of failure were slippage and I have not had any slippage at all. None. So...hummm....

Hoping for some more input. Thanks again for your experience with this.

Green Mesa XJ
September 27th, 2017, 16:39
Torque converter may or may not be failing, Iím not too familiar with what the symptoms would be. Our trouble was it was disengaging (un locking) at hwy speed. No trouble with since replacing those two parts and itís a 300k mile jeep. I also didnít try to trouble shoot just picked up the parts and drove to where they parked the jeep. It never failed, they got to where they were going.

On the 91-95 the brake light switch sends signals to the lights, torque converter and cruise control. Not sure what changed in 1996.

Sent from my iPhone using Tapatalk

September 28th, 2017, 14:36
Today I was driving at 70mph and I tapped the break while holding the gas. The torque converter disengaged and the RPMs went up, just as I would expect.
When the torque converter disengaged the loss of power was gradual. When my XJ "hiccups" it is sudden, immediate, and a total loss of pulling...for a split second. It just "hiccups" then drives normal.

WTH is going on? Anyone???? Please???


Green Mesa XJ
September 28th, 2017, 16:32
Is you fuel pressure testing right?
Reminded me of a carbureted car eating the fuel faster than the bowl fills. I know it not applicable here with fuel injectors.

Didnít quite seem like the transmission or transfer case slipping, still kind of leaning towards torque converter but I maybe totally wrong, hopefully someone who has had this happen can point you the right direction.

Sent from my iPhone using Tapatalk

September 28th, 2017, 16:49
When my TPS failed the symptoms were as follows:

1. Taking foot off gas pedal, to coast on an exit ramp, RPM's went up enough for me to notice, like 1000 RPM or something. It was like it was downshifting to decelerate.
2. On cold start, RPM spiked to 3000 RPM.
3. Engine felt like it was cutting out for a split second. It did this repeatedly on my drive home from work. However, it was for such a short amount of time I did not lose power.

When (3) was occurring on my way home from work I purchased a new TPS from the dealer. All symptoms went away and haven't come back. That was a couple of years ago.

I suppose you could test the TPS sensor when its hot. I think you need a graphing multimeter, scope, or analog meter to ensure there are no cut outs.

September 28th, 2017, 17:35
Thanks MD. I was thinking torque converter or TPS. $90 for an OEM TPS. I suspect that is my next move.
Thanks again.

September 28th, 2017, 19:17
This is sort of a re-post of the same problem I have been having for some time.
'00 XJ Sport, 4.0, AW4 tranny. Stock except for OME lift.

I commute, at 80mph, 36 miles nonstop, each way daily. Recently the jeep has been "hiccupping" for lack of a better term. It stops pulling for just a second. The cruise control is usually on, but it does it under foot-throttle as well.
It does it more when it is hot outside. In the mornings....maybe once. In the afternoon about 6 times in 36 miles.
Sounds like problems I had with one of my ignition coils. As the engine heated up the coil winding would start to separate. Eventually it just crapped out on the side of the road. Once it cooled off I was able to limp it home (misfiring the whole way)

September 28th, 2017, 22:41
Thanks MD. I was thinking torque converter or TPS. $90 for an OEM TPS. I suspect that is my next move.
Thanks again.

Hope that helps, let us know the final solution. The TPS is more a less a pot that wear outs over time. It seems strange that a JY TPS would have the same problem, but maybe it drove the same roads you did. TN I-40 @ 80 MPH is very, very common unless you're going through the Nashville downtown loop at rush hour. lol. I almost wonder if its not an O2 or something like that. These Jeeps switch from closed to open loop fairly often. Above 60-75% throttle they will go open loop. IF you had a scanner that did live data it would probably help. But it doesn't hurt to have a fresh good dealer TPS either. Keep the spare under the drivers seat with a spare crank and cam sensor. :)

September 28th, 2017, 23:09
I'd be another vote for heat fad on your coil the symptoms and conditions all fit

September 28th, 2017, 23:37
2000-2001 have the coil rail. Very much different than 1999 and earlier.

September 29th, 2017, 04:47
OP, do you have any codes for misfire?

September 29th, 2017, 14:28
No codes AT ALL. Go figure. Since I have replaced my head due to misfires, I recognize what misfires feel like. This is much more sudden and more clunky. It is like EVERYTHING disengages for half of a second. The nose of the Jeep even dips for a split second. It sort of goes "clunk," stops puling just for a moment, and then proceeds as if nothing had happened.
The most significant thing I can see is that rarely happens in cool weather, but happens every couple of miles when it is hot outside and the engine is hot.

Grrrrr. I have a replacement Echlin coil rail and I still have the original OEM, which is probably not bad. I'm planning on replacing the TPS (ordered already), replacing the plugs, and putting the OEM coil rail back on. If this does not fix it.....perhaps it is the tranny. I don't think it is the torque converter disengaging, because when I tap the brake under speed and force it to disengage, the disengage is very smooth and the loss of power gradual.

What I am experiencing is like someone turning the key off and back on, under speed, for a split second. As soo as you feel the hiccup, it is back to running normal.

Thanks for the suggestions. When I figure it out I will post the solution.

September 29th, 2017, 14:44
Test/ inspect /replace :
charging system - battery , cables, alternator,
Igntion system- ignition switch, coil, ignitor , inspect/replace spark plugs and wires
fuel system - fuel pump, regulator, fuel filter
ENgine management sensors that come to mind: TPS and the CPS , coolant sensor, and o2 sensor
change trans fluid and inspect fluid
clean and inspect all grounds and sensor connections

also, you can probably wire the TC to a switch and cut it out of the computer altogether, and see if that helps if all else fails.

I would try to test every sensor. I had a similar issue when the coolant temp sensor was going out on my MJ years back. It would start randomly dying on me sometimes, very hard to diagnose. once we finally caught it in the act, we saw the coolant sensor would ramdonly read -15* or so out of nowhere, dump a ton of fuel, flood the motor, and kill the engine.

September 29th, 2017, 15:21
Thanks again for the tips (blondejon). I will cover some of this with the plugs/rail/TPS coming up. I put new filter, fluid and gasket in tranny two years ago and fluid is nice and pink and at proper level.

Fuel system could be the issue. Especially fuel filter.....except the obvious question: Why would this only happen when it is hot? So I have looked past pressure/filter to this point.

I noticed that the battery gauge looks like it is running at 13.5 volts instead of 14. I seem to remember the gauge running straight up at 14 volts in the past. Obviously the dash gauge is not accurate to .5 volt measurements. Obviously. But if it seems "different" it is probably worth looking into. Curious if the testing equipment at AutoReillyAdvance can accurately test an alternator? Is jamming my volt meter into the leads and reading output voltage any better?

My engine is not dying at all. Not even trying to die (knock on wood). It could be a temp sensor, but I am pretty anal about cooling systems. I have a replacement Mopar sensor from 5 or 6 years ago. And all components are in good shape, have been flushed, have good fluid, etc. But.....HEAT is part of the issue...so there's that.

Battery ground has always been shifty. Can't hurt to check it out while replacing coil rail and plugs.

September 29th, 2017, 16:58
Trans has nothing to do with engine power

Do your indicator lights stay lit when it happens?

September 29th, 2017, 22:22
It is not a loss of power, so to speak. It is more like the drivetrain disengages for a split second. Or all spark is lost for a brief moment. Or the fuel is cut off for a split second. This is more of a brief hiccup.

The CEL NEVER comes on due to this issue and it has NEVER thrown a code due to this issue. If by indicator lights, you mean does the dash stay lit and does the radio keep playing...YES. They do. There does not appear to be a loss of electrical.

September 30th, 2017, 04:48
If the cabin electrical stays on then you can exclude the battery or alternator (probably not anyway)

Crank and Cam sensors will kill the engine just like somebody reached over and turned the key off. Sometimes they go intermittent before dying completely. Have you already reaplaced them? If not you might want to buy them and use your old ones as spares. Swap one at a time so you can debug.

Green Mesa XJ
September 30th, 2017, 08:34
The 2000 XJ have that in-line ignition coils for each cylinder right? If thatís failing That might explain it.

Iíve heard of bad alternators causing all kinds of problems with our jeeps, not sure about this particular symptom.

Fuel system might be something it were some how intermittently starving the fuel supply.

My f150 had bad injectors that would cause a hiccup, no CEL or codes, in that case itíd be brief almost like a misfire feel, then back to normal. But if I put my foot down the truck would fly so it didnít lack power from the other cylinders. Eventual it did this more and more in the driving range, but it also could go 200 miles on a trip and be fine. Found out later that year truck had a batch of bad injectors, Ford in their generosity had a program to replace one injector at a time if they found a faulty one instead of eliminating the problem all together.

Sent from my iPhone using Tapatalk

September 30th, 2017, 08:56
Has new Mopar Cam sensor. The crank sensor is a couple of years old but it is Napa, not Mopar.
I am putting the OEM ignition rail back on today. I replaced it with Echlin a few years ago trouble shooting, but it wasn't bad. It is in my garage.

Could be a bad injector. Very possible. And it does feel like almost like a misfire, then back to normal.

Keep in mind this only happens when it is hot outside and the engine is hot. I was just idling my jeep for more than 30 minutes, but it is cool outside. It ran great. Hummm.....

September 30th, 2017, 09:50
The sensors are likely to fail when hot. You might also do a compression test and see what the results are while you're changing the coil rail.

September 30th, 2017, 14:53
My wife has a 2010 Mazda CX-9 with 185k miles exhibit similar symptoms. After changing the lifetime transfer case lube, which is a total pia, flushing the tranny and rear end, checking all u-joints, it still did it. And no codes. One day I was really hammering the gas pedal to try to get it to happen, finally got a check engine light, sustained loss of power and was able to pull codes. Can't remember the code, but it pointed to a misfire in cylinder 2. This V-6 has COP and #2, when pulled had overheated and leaked its cooling oil making the top ceramic part of the spark plug wet. Bought a $60 COP and it had been perfect. Long way of saying I would lean toward the coil rail as well based on what you describe.

Sent from my iPhone using Tapatalk

September 30th, 2017, 19:10
I had something like that happen to me. I would drive for a while at like 75-80 and out of the blue it would drop into 3rd. Wouldent get back to od. Turned out to be mis adjusted shift cable. Easy to check just time consuming.

Sent from my iPhone using Tapatalk

October 1st, 2017, 06:55
Has a rebuilt TUPY head from a Wrangler. Replaced about 3 years ago. Should not be any compression/valve issues. When I pulled the plugs yesterday, they had all worn evenly and looked nice.