Alpine highway power ( od/passing gear)

So I've recently been on some long journeys to southern CO mountains. I've done this trip many times in my 99 auto.

Two different motors. Currently low end power is usual and everything is normal until climbing highway passes and it bogs to 40mph and doesn't want to hit overdrive/ passing gear, whatever it is, until it drops below 40mph. Once and a while it'll give it up and scream the RPMs up to fight up the hills, like it should.

I've done this trip on 33s 4.56s lots of times so I'm trying to learn what I'm looking at for this power change in my trips.

New motor is 95/92 vs the old 99 and its pretty similar power, but the older had a little more scoot before they tightened emmissions based changes. The TPS is new Mopar and I've been messing with the throttle cable adjustment lots to compensate/ try for different throttle responses. Today i maxed out the cable by placing the plate at W.O.T. by hand, rather than the pedal. It shifts smooth and seems to access O.D. a little easier, but the old engine would constantly be trying to shift down for passing power on these roads, it fought to Scoot up these passes. Something isn't giving the sane fight response for the jeep taking on mountain passes.

Flat ground ground I can rap out to high mph easy. I know jeeps struggle in CO, but with 226000 ish on the rig, what would I look to for a difference?

I'm not really sure where to aim with this rigs age.
Injectors, trans, cat?....

Injectors-bwd 4 hole
Cat- stock
Exhaust manifold- banks, straight pipe other than cat.
99 all other parts bolted to motor
Aw4-stock
Up stream 02- ngk,
Downstream bosch
aw4 fluid level good and color good.

P1391 code still, even with new harness. No change or hiccups, the only thing is cel stays on other wise you'd never know it's there.




What do you all think?

All by myseleyyeeeeellyf.....

Power+ big hills= lacking did I say something off here guys?

No ideas or thoughts on the matter from all the views Lol?



Thank you for anything you can point toward guys.

The throttle-to-tranny cable doesn't affect when it shifts. It controls the pressure in the trans and hence the firmness of the shift. The trans computer uses the rpm, speed and throttle position sensor to decide when to shift.

lawsoncl said:

The throttle-to-tranny cable doesn't affect when it shifts. It controls the pressure in the trans and hence the firmness of the shift. The trans computer uses the rpm, speed and throttle position sensor to decide when to shift.

Click to expand...

Throttle to throttle valve cable I believe I should have said?

Ugh, dare I ask does the TCM take its RPM input from the ckps?
If not what else would tell the trans to rev up to high passing gear ?



Thank you

4x4JeePmaNthINg said:

Ugh, dare I ask does the TCM take its RPM input from the ckps?
If not what else would tell the trans to rev up to high passing gear ?
Thank you

Click to expand...

The trans computer uses the output speed sensor on the back of the tranny and the throttle position sensor to determine shifting. 98+ adds another sensor to the front of the transmission which is uses primarily as a diagnostic to determine if something is wrong, for example the t/c isn't locking up or the trans doesn't appear to be in the gear commanded by the electronic shift solenoids.


So #1 culprit for not upshifting/downshifting when its supposed to is the TPS sensor. The rear output sensor rarely fails, and when it does you typicaly never upshift out of 1st. If it's skipping gears (in particular 2nd) or not start out in 1st gear, then the shift solenoids may be going bad. Both solenoids are off in 4th gear, and they're both on in 2nd gear.

Hmmmm. Buy Mopar they say, doesn't like other sensors they say........money racket. If it's tps it's staying in, it drives normal in all othersenses noises aside.

I have to press the pedal into the floor quite firmly to get the od gear to respond on command.

Thank you for the guidance, I'll be keeping an eye on this.

4x4JeePmaNthINg said:

Cat- stock

What do you all think?

Click to expand...

Is this the original CAT? I remember checking it with the vacuum gauge, it passed the criteria for a plugged exhaust. When I put the gauge on my engine to show you the vacuum leak, I revved the engine and let the throttle snap shut. The needle shot up faster, and higher than it did on your engine. I wonder if it is possible to have a partial restriction and not set a code.

Past that, I learned long ago to manually shift into second and let the engine make more power. I discovered that it takes less throttle to maintain that RPM/speed.

It is the stock cat. I gave it a few hours with a hammer to listen for rattles, but nothing.

They used different cams in some different years. That will change your torque curve. Might want to hit Wiki and see if yours are different.

old_man said:

They used different cams in some different years. That will change your torque curve. Might want to hit Wiki and see if yours are different.

Click to expand...

Interesting, I shall indeed.

old_man said:

They used different cams in some different years. That will change your torque curve. Might want to hit Wiki and see if yours are different.

Click to expand...

I thought about the same thing but I didn't see any info on the condition of these motors so there wasn't anything to compare to.

4x4JeePmaNthINg said:

I have to press the pedal into the floor quite firmly to get the od gear to respond on command.

Click to expand...

I'm not sure what you mean by "od/passing gear". Are you talking about it not downshifting when you floor it? Usually that would be the TPS, which you can and should test with a meter. If it's very slow completing the shift that would be the cable between the throttl body and the trans being misadjusted. You mention playing with the throttle-to-pedal cable too. Is it actually opening the throttle all the way when you mash the pedal?

lawsoncl said:

I'm not sure what you mean by "od/passing gear". Are you talking about it not downshifting when you floor it? Usually that would be the TPS, which you can and should test with a meter. If it's very slow completing the shift that would be the cable between the throttl body and the trans being misadjusted. You mention playing with the throttle-to-pedal cable too. Is it actually opening the throttle all the way when you mash the pedal?

Click to expand...

So when going up hill the vehicle will shift down to compensate. Then there is what I assume is overdrive or some such gearing where the vehicle really shoots up the RPMs to give it Hell up passes. This is what doesn't go as smoothly as it used to and is a but difficult to engage.

The cable I'm referring to is the only adjustable cable on the T.B., to my knowkedge.

If it was the T.P.S.(new Mopar only months old) why would it only do this going up passes?

4x4JeePmaNthINg said:

So when going up hill the vehicle will shift down to compensate. Then there is what I assume is overdrive or some such gearing where the vehicle really shoots up the RPMs to give it Hell up passes. This is what doesn't go as smoothly as it used to and is a but difficult to engage.

The cable I'm referring to is the only adjustable cable on the T.B., to my knowkedge.

If it was the T.P.S.(new Mopar only months old) why would it only do this going up passes?

Click to expand...

Actually, the over drive will slow the XJ going up steep hills. You (and it usually do) want it to come out of OD.

Now put that aside, I did not see where you said you shifted it manually to 3 or 2 when the AW4 do not down shift on it own the way it is supposed to do.

As indicated in earlier posts, there may be something wrong with the engine itself, the exhaust system, the fuel delivery or something else or a combination of several. Start by manually shifting the AW4 to rule out mechanical problems with it. While doing this, you will also find out if the engine is up to the task.

If it were mine, I would do the following 2 Tips. BTW, cats can be plugged up and not rattle.....

http://cruiser54.com/?p=58

http://cruiser54.com/?p=98