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Giving it gas, not going anywhere

2K views 23 replies 7 participants last post by  aldersonfilm 
#1 ·
Got a 1998 TJ with an automatic. It's been acting up a bit recently. The other day, I pulled out of a parking lot and put my foot down, but the engine didn't rev up and the jeep was just creeping along. Then all of a sudden it sort of lurched forward, like a hard gear change, and went back to normal for the rest of the trip. Possibly and probably related, we were on a rocky trail with the jeep in 4hi and came up to a small boulder field. As I was trying to power over one of the rocks, the Jeep seemed to do the same thing again. I had my foot down it it reved up to maybe 1500 RPM at most, but with my foot to the floor it wouldn't go anywhere. No tire spin at all. I had to back up and decided it was a good time to shift to 4lo and then it crawled right over like normal. TPS maybe?
The transmission does whine a bit, especially in first gear, but it has for as long as I've had the jeep and I've kept the fluid level normal. It has also started making a faint rhythmic droning/growling when cold and in reverse... Getting ready for the Rubicon. Not a good place for something major to decide to give up.
 
#3 ·
With the jeep hot, in neutral after cycling through the gears on a level surface. ATF looks a healthy red and doesn't smell burt. Checked it just now and it could be low, but honestly, it is nearly impossible to read that dipstick. There's definitive line of fluid, so it's hard to tell. Any good ideas on getting an accurate reading?
 
#5 ·
I have noticed it getting starved offroad. At least I assume that's what's happening. In Moab, I noticed several times on the super steep slip rock, it would suddenly roll way back down the hill if I let off the gas for even a second. I guess I could just wing it and toss an extra quart in. Worst case scenario it blows out the vent right? It does seem to be leaking some fluid from somewhere and collecting on the pan. Not a lot, just some seepage. Replaces the gasket on that about a year ago or so.
 
#6 ·
X2 on BIff's advice, throw in a quart of ATF+4. That your transmission is starving out/sucking air on steep climbs is a good indication it's low on ATF. Since it's low enough to cause problems, it may not be a bad idea to throw in 2 quarts. One to bring it back up to level, the other to overfill it for climbs. You're right it's hard to get a good read on the dipstick, I sometimes dip it a half-dozen times to make sure I'm getting an accurate indication.
 
#7 ·
Dropped a quart and a half in. As best I can tell on the dip stick, it's slightly above max. Yet, as soon as I took it out, it seemed to bog down again in first. Only does it when first driving off, going from first to second. It's like its hesitating going into second.
 
#11 ·
FSM.

FRONT BAND ADJUSTMENT
The front (kickdown) band adjusting screw is
located on the left side of the transmission case
above the manual valve and throttle valve levers.
(1) Raise vehicle.
(2) Loosen band adjusting screw locknut (Fig. 179).
Then back locknut off 3-5 turns. Be sure adjusting
screw turns freely in case. Apply lubricant to screw
threads if necessary.
(3) Tighten band adjusting screw to 8 N·m (72 in.
lbs.) torque with Inch Pound Torque Wrench
C-3380-A, a 3-in. extension and 5/16 socket.
(4) Back off front band adjusting screw 2-1/2 turns
for the 30RH and 2-1/4 turns for the 32RH.
(5) Hold adjuster screw in position and tighten
locknut to 41 N·m (30 ft. lbs.) torque
REAR BAND ADJUSTMENT
The transmission oil pan must be removed for
access to the rear band adjusting screw.
(1) Raise vehicle.
(2) Remove transmission oil pan and drain fluid.
(3) Loosen band adjusting screw locknut 5-6 turns.
Be sure adjusting screw turns freely in lever.
(4) Tighten adjusting screw to 5 N·m (41 in. lbs.)
for the 30RH and 8 N·m (72 in. lbs.) torque for the
32RH (Fig. 181).
(5) Back off adjusting screw 7 turns for the 30RH
and 4 turns for the 32RH.
(6) Hold adjusting screw in place and tighten locknut
to 34 N·m (25 ft. lbs.) torque.
(7) Position new gasket on oil pan and install pan
on transmission. Tighten pan bolts to 17 N·m (13 ft.
lbs.) torque.



__________________
 
#12 ·
My Jeep was having the same problem as yours, foot to the floor and it wouldn't move much, then randomly is would engage and I'd start moving. I had a CEL with the code of Throttle position sensor voltage to high. I just installed a new tps and connector and everything is great now.

I work at a dealer and the older techs were telling me that this is a problem tjs have. I asked one how many times he thinks he had replaced the tps and connector on customer cars and he couldn't even put a number to it he had done so many.

There are tests you can run at home to determine if the tps or connector is bad. Disconnect the tps and at the connector use a multi-meter to check the resistance between the tps signal circuit and the 5 volt supply circuit. If the resistance is below 5.0 ohms then you'll most likely need a new tps and connector.

Let me know if its running at 5 volts and I'll let you know the next test you can do.

Also have fun running the Rubicon! My buddy just got back from it and he had a great time!
 
#15 ·
Test it out and find out! If its the tps I would highly recommend getting a new connector as well as tps, you just have to solder 3 wires. A tech I talked to said most of the time people would just replace the tps and it wouldn't fix it, then they replace the connector and boom good to go.
Question for you also, do you have cruise control? Does it work? Does your horn work?
 
#17 ·
He was asking about those other items because the steering wheel electrical connector called the clockspring which connects the horn, cruise control buttons, and air bag, can cause issues for the TPS by putting electrical noise on the circuit.

Though I can see a bad TPS causing problems with erratic idle, acceleration, etc., I'm not sure how it could cause the engine not to rev at all. There is a mechanical linkage between the gas pedal and throttle body valve plate and stepping on the gas pedal opens that valve plate which lets air in which will raise the engine RPMs. Remove the air intake from the top of the throttle body and verify the TB's valve plate is opening up when the gas pedal linkage is moved or the throttle cable is pulled.

That big round plate in the throttle body's opening...

 
#18 ·
Yes the clockspring can sometimes be the culprit if your cruise and horn don't work, but most likely if you have a bad clockspring your airbag light will be on. A bad tps though can also cause your cruise and horn to not work.

Jerry, my throttle opening was perfectly functional when I had this problem. When I had the problem even if I had my foot to the floor it would hesitate for a few seconds, then all the sudden it was like the tps finally figured out I needed more air to move the vehicle and it would start moving normal again.
 
#19 ·
Keep in mind that the throttle cable rotates the shaft that opens the valve plate, which rotates the TPS's input shaft. Neither the TPS nor the PCM does anything to give the engine more air, that's the job of the gas pedal via the throttle cable. The TPS only reports to the PCM when the valve plate is opened by the gas pedal, not the other way around. :)
 
#20 ·
Did it again today. Only happens when I first start driving, once. It will rev up a bit, but only to a point, the more I press the pedal, the more it seems to actually bog down, almost like it's losing power. Then it just jolts into action.
The Airbag light is on, it was coming on an off randomly in the past month or so, and now it's pretty much on all the time. The horn doesn't always work either as I recall.
Correct me if I'm wrong, but if the throttle wasn't opening properly, I should have this issue all the time, right? It only happens once shortly after start up, before the first gear change.
 
#22 ·
So update. We are up by the Rubicon now, getting ready to do the trail. Throttle response seems good, though it did seem to bog down a little bit as usual even after the TPS.
But now I've got ATF leaking everywhere. It was leaking soon after I filled the tranny with an extra quart and a half as discussed earlier, but not too much. However, after our 6 hour drive up here, it is leaking A LOT. So much so, that it appears to have soaked the front of the rear diff and the gas tank in fluid on the drive up. I left it parked for two days since and there is a dinner plate sized puddle underneath the tranny pan. I know you guys said it was safe to overfill it, but I did a little more research and some said that overfilling and driving at highways speeds could blow out the seals and build up foam that reduces the fluids lubrication properties. We're doing the trail in four days, and I'm a ways from home now. Any thoughts?
 
#23 ·
It's definitely safe to overfill it up to a point but there is vent just above the front input shaft that excessive ATF could be leaking out of, on the front of the transmission.

Your next step needs to be to figure out where the ATF is coming from. Start the engine and shift into Neutral and check your ATF level... is it still ok? If so, perhaps the ATF is just leaking out of its front air vent hole and it'll stop at some point. A little leaked ATF can blow around and look much worse than it really is but you really need to isolate where it appears the ATF is coming from. Clean everything off with brake cleaner and then watch it closely afterward to see if you can't pinpoint where the ATF is actually coming from.
 
#24 ·
So cleaned off the underside as best as possible and waited an hour. Came out to see a couple drops. One from the very front underside of the bell housing (looks like the rear main seal area) and one from the back driver's side of the tranny pan. It appears to be seeping out of or near a sensor that threads into the driver's side of the transmission, possible a speed sensor? It that something with an o ring that could be easily changed? Can the rear main seal leak tranny fluid as well as engine oil? It seems to be leaking both. Hesitant about running the rubicon with how much fluid is coming out while the jeep is off. It was running pretty hot the entire trip up here too.
 
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