More very bizarre problems on my 1994 Montero SR:

A couple months ago, I had to replace the Idle Air Control due to idling issues and engine staling out. Replaced the IAC with a non-OEM brand, and she was running good, and finally idling down to around 800 rpm. A couple days ago, there was some irratic idling going on. When coming to a stop, the rpms would climb up to about 1800, then drop back to about 1200, then up to 1800. However, on the highway, she drove fine, and the transmission was shifting perfectly.

Today, the engine once again would not idle, but would stall out unless I kept my foot a bit on the pedal. So, I figured that maybe it was a bad Throttle Position Sensor.....so I put a new TPS on, and cranked up the engine.......did not solve the issue, as she still would stall out and not idle. So, I went ahead and took off the 2 month old IAC, and replaced it with a used one that I knew was good. Yep, that solved the problem, and she was idling good. So, I took her for a quick test drive.
As soon as I got on the highway, and the tranny shifted into 2nd, it started slipping and not getting power to the wheels. I felt that it was not going to make it up a slight grade, and pulled into a neighbors driveway. It seems to have plenty of power when starting off in 1st (this is an automatic), but once she gets going and automatically shifts to 2nd, there is slipping and lack of power going to the wheels.

Does anyone have any suggestions as to the problem? Why would the tranny suddenly get all goofey after replacing the IAC and TPS? Does the computer send any signals to the tranny that might cause this.

Could it be one of those 3 sensors inside the tranny? See pic below:
(I took pic last year when servicing the tranny.....and I never replaced those 3 switches/sensors)

I just did a complete tranny fluid/filter change about 2000 miles ago, and it has been working perfectly. I am baffled. Help....................................

 

StudebakerHawk, why can't you ask something easy like - "how many cylinders my car has?", or - "should I replace spark plug wires?"... You always have the hardest questions
JK...
Anyhow, you got another puzzle on your hands. It is possible to have a bad solenoid, but question, is why? and which one? I would hold off on the urge to pull the pan and start swapping solenoids. First, confirm and isolate the issue. Check fluid level and condition, then run transmission pressure checks in all gears. There is a test port in the tranny. Plug transmission pressure gauge in there and run the tests (you have to find test specs and results interpretation table for your transmission). Then you will know if it is a pressure control solenoid or 2-d gear solenoid or something else that had failed. Then proceed from there. That is what I did with my daughter's car, when it lost transmission.

 

Hey Hunter, When you started talking about pressure it got me thinking. Isn't there a second cable running from the throttlebody to the transmission that controls/regulates pressure in some way. This one is out of my league but I believe I heard this somewhere on this forum.

 

This is way above my knowledge too. As far As I'm aware, line pressure can be controlled via vacuum or mechanical cable on older transmissions. On newer ones it is done electronically via a line pressure control solenoid (on/off pulsing).

 

Hunter: I agree with you.......I have been having some really bizarre and hard problems to deal with. I swear there are gremlins in my garage doing all this wierd stuff......half of which I have not even posted here. Sometimes I think Im going crazy......ha ha. In this case, why in the world would the perfectly working tranny do this right after I replaced the Idle Air Control and Throttle Position Sensor? I still need to dig into the big shop manual and see if there are any suggestions there.

When Naeos mentioned the pressure line/vacuum line/or something maybe running from the throttle body to the tranny, made me jump. I went to the garage to see if any hoses were off, but all looked good.....dern it, I thought that it might be an easy fix.

I checked the fluid yesterday after this happened......engine was warm and I ran the shifter through all the gears before checking. The fluid was exactly up on the correct mark. Crawled underneath, and its dry as a bone.....not a drop of tranny fluid nor engine oil anywhere.

So, I will dig into the shop manual, and get back to this post when I have something solid.

Thanks for all the tips/advice from all.

 

I was reading through the Shop Manual for my 94 Montero......pretty confusing. It seems to say that the Throttle Position Sensor also controls the tranny shifting......along with Water Temp sensor, Oil Pressure Sensor, Speed Sensor, etc.......seems like alot of sensors all over the engine have input to the tranny to tell it what,when, how to shift. Is this crazy, or what?

However, this is making me think that this tranny problem is directly a result of my replacing the Throttle Position Sensor just before this tranny problem happened. Since the new TPS did not have any affect on the Engine Idle problem, I think I will try taking out the new "knock-off brand" one, and re-installing the OEM TPS that I removed. Does anyone else agree that this is worth a try?

What happened to the good ole days......when you put the tranny in Drive, it just worked.......and did not need data from all these other sensors?? Maybe just that throttle "kick-down" linkage and a vacuum line. Back in the good days.

 

Forgive me if you already did this, but did you calibrate the TPS when you replaced it? There should be some white paint on the old TPS that should correlate with some on the throttle body. There should be instructions in your book on how to calibrate it with a multimeter otherwise.

 

Naeos........Thanks for asking that question. I had no idea that you had to "calibrate the TPS" when installing it. These just have 2 screws holding it in place, but the 2 screw holes are oval shaped, so it can be adjusted a bit clockwise or counter-clockwise. I just installed it, and with the engine running, I tried the entire range, but there was no difference in the engine rpm.....so, I just opted for the middle position.
I will check the shop manual about this........I had no clue. I will also look for that "white paint" you mentioned.

However, Im pretty sure that the adjustment screw for the butterfly inside the throttle body does have paint on it, and it should never be changed from the factory setting.

Will post again after I dig into the manual.
Thanks again for your comments.

 

Oakkie Doakkie.........Me gots some answers! Good news for me.

Naeos was totally right about calibrating the TPS. I grabbed the huge Shop Manual and found the section about installing and re-setting the TPS. Here is Page 1:




Page 2:




Bottom of Page 2:




And a picture of the Montero Throttle Body/etc.:








In summary, you have to loosen the TPS screws and then rotate it all the way clockwise, and have a .65 mm feeler gauge stuck between the SAS and throttle lever. Then put the meter on the the two bottom terminals ( 1 and 2 as referred to in Manual), and slowly rotate counter-clockwise until there is no continuity. At this point, tighten the two TPS set screws. I did not do any further testing as the manual indicated.

Took the Montero for a test drive, and the Tranny functioned perfectly! It is pretty darn amazing (in my feeble mind) that just having the TPS a bit out of adjustment will have such a detrimental affect on the transmission. Yesterday, the tranny felt as if all the internal plates/bands were just slipping as the tranny tried to shift from 1 to 2. Today, a quick calibratiion/adjustment of the TPS solve the tranny issue!

Im one lucky camper.....I was thinking that maybe some trash had worked loose inside the tranny and was clogging some small passages/ports, and there could be some major dinero being spent to get it right.
Thanks Naeos and Hunter for your advice.

Some other input for future readers having this issue: I read someplace in the manual that you should never try to adjust that SAS screw....it is factory calibrated and should not be messed with. Maybe someone else can explain why this is the case. Any idle issues should be addressed with the IAC "Idle Air Control" valve first, as that is usually the problem with stalling or too fast idle. The IAC is located below the TPS (but you cant see it in these pictures).

Hope this helps others down the road.

 

Glad you got it worked out! I may even use this to calibrate my TPS. Thanks for posting those pictures of the manual!