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TPS questions

R

RaccoonJoe

NAXJA Forum User
Location
Fort Wayne, IN
OK....I took the 89 XJ into the Jeep dealer in town for a recalled TPS sensor yesterday. They replaced it without giving me any grief....but now I'm seeing some problems.

1st. When I went to leave the dealership, I couldn't get the damn thing to idle. it would idle much lower than it's normal 300-500 RPM, low enough that the tach would actually hit zero. I also had quite a bit of stumble and hesitation when hitting the skinny pedal (in park). When coming down off a high rev, the motor would stall out, every time.

2nd. Drove it around town for a while, and the idle issue seemed to improve. I had been told that you need to drive around for a while when replacing TPS, to reset the computer/sensor. Stumble and hesitation improved slightly.

3rd. On my way to work this AM, I noticed the immediate rev up to 2500+ RPM. (I thought the TPS was supposed to fix this problem??) Also, the stumbing/hestiation issue remains, both with motor cold and hot. More troubling, I noticed some shifting issues. It will no longer downshift on it's own. I go to pass someone, moving 35 MPH.....give it some skinny pedal, and the RPMs go up slightly, but no shifting, and no acceleration. I also seem to have lost OD. Highway cruising (~65 MPH), and I've noticed that RPMs are ~500-700 higher than usual.


Any advice as to what I should do here?? I know Renix Jeeps are a breed all their own, and I don't think the dealership has any Renix mechanics.
 
Since when are Jeep replacing TPS's? I have an 89 and I don't think the TPS has been replaced. I live in BC, Canada btw.

Also, search for Renix TPS, and then from one of the threads, do the tutorial for setting the TPS on an auto tranny. (You need a voltmeter for this btw)
 
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mattbred said:
Since when are Jeep replacing TPS's? I have an 89 and I don't think the TPS has been replaced. I live in BC, Canada btw.
Click to expand...

I hit up the dealer for an option sheet...also happened to ask about any outstanding recalls. Turns out that mine was covered under a TPS replacement.....



FYI...always check for recalls. Turns out my previous DD (96 s-10) had a recall because of a rear diff problem "causing the rear wheels to lock at highway speeds, leading to possible loss of control"
 
I suggest do a seach on here for TPS Adjusting or something (make sure you don't just put TPS, the seach feature here needs 4 characters or more i believe). There are many detailed threads and links to pictures and things on how to adjust these bad boys using a simple voltmeter. I admitedly have yet to do my new one, but the Jeep is operating "Okay", the idle is just low and won't go up. After I move i plan on doing said adjustment, I'll post up here how it went! I might also consider taking the IAS (located next to the TPS) out and spraying it down with either brake or carb cleaner, and a quick shot of the WD40. I'm also going to perform this task very soon, which I'll post up the results on. Good luck, let us know what happens!
 
To save on search time, I have this one always on hand:
For an 87-90 4.0:

Test is done with throttle closed, connectors connected, ignition on, engine off. Insert probes through back of connectors to make readings. Use a high impedance meter. Adjust TPS by loosening mounting screws and turning in mount.

For manual connect + probe to terminal A, and - to B. Take a reading, which should be in vicinity of 5 volts but probably lower. Note the reading well. Now move the positive probe to terminal C. The reading should be 16 percent of the previous reading.

For Automatic, use the square, 4-terminal plug. Connect probe + to terminal A, and - to D. Note reading, which should be in vicinity of 5 volts. Now move probe + to terminal B. This reading should be 82 % of the first.
Click to expand...

My guess is that they did not adjust it at all, if they have no "Renix mechanics" left around. The Renix engine computer does not learn anything. Driving around will not make a bad adjustment better. On Automatics, the TPS has two sections, one of which controls the transmission and one the engine, so shifting issues from a misadjusted or defective one are not surprising. Make sure you use the correct procedure for yours, and adjust it using the tranny section, not the engine section.
 
Time for an update:

After driving for 2 days (~150 miles), I've noticed a few things. The high rev on start-up seems to be evening out around 2000 RPM. I still have a very low idle, but no misfire/sputter on idle. When still in park, if I try and rev from idle, it will spit/sputter/misfire until ~1500 RPM, then we're good. While this always happens, it does seem to be worse when the motor is cold. Also, when the motor is hot and I try this, it backfires out the intake....I can actually feel the *puff* come out the front of the air cleaner box.

I'm still having troubles with the Jeep not down-shifting...and still don't have overdrive. I was playing with shifting it manually, by using the 1-2, 3, D settings...and it seems to skip 2nd gear?? That could just be me, tho....



The skinny on this: I'm going to be doing some pretty intensive sensor testing on Saturday. TPS test/calibration, MAP, IAC cleaning, "detent cable" adjustment, cruise adjustment....basically anything I can get my hands on. Does anyone have any suggestions as to where I should start??
 
I would definitely start with the TPS adjustment, since that does affect a number of the problems you're having. In my experiments a few years ago with an 87, I found that an output voltage slightly too high (measured at the tranny section as specified) resulted in spitting or backfiring coming off idle.

Cleaning the idle air controller is a good idea. So is a thorough check for vacuum leaks, dislodged hoses, etc. If you got some knuckledragger at the dealership who doesn't even know that the TPS needs adjustment, it's probably a good idea to second-guess everything, and look for other mistakes.

If you think the cruise adjustment is contributing, just disconnect it temporarily.

The transmission cable adjustment is very simple, so it's a good idea to do that whether it needs it or not.

Owing to the way the AW4 shifts, it can be difficult, especially if you don't have a tachometer, to figure out which gears it's choosing. In normal position, the torque converter should lock on both 3 and 4. On my 87, depending on throttle usage, it could go 1-2-3-lock3 - 4 (shifting without apparently unlocking), or 1-2-3-4-lock, or even 1-2-3-lock 3-unlock 3-4-lock.
 
Cruise adjustment isn't contributing (I'm pretty sure), it's just that when setting the cruise, the Jeep *always* speeds up by ~5MPH. Not a big deal, just annoying.

From watching my tach, it would appear that my transmission shifts almost 6 times. That's just counting the number of times that the RPMs will drop when accelerating. (used to driving a manual, and actually being able to control these things...=P) I'm basing my conclusion of "lost overdrive" off 2 facts.
1. Higher than normal RPMs at highway speeds.
2. Before the new TPS, the tranny would slip (motor would rev ~200 RPM), then it would shift rather hard into OD. I'm not getting that anymore....



I think the low idle is a combination of vacuum leak and IAC, but not sure. I *will* be running a complete vacuum inspection/testing this weekend, however, just to be sure. The low idle isn't concerning me too much, but I know that vacuum leaks can wreak havoc throughout the entire system......
 
What does the dealer have to say? If these issues didn't exist before they "fixed" it, I'd be all over them.
 
xjbubba said:
What does the dealer have to say? If these issues didn't exist before they "fixed" it, I'd be all over them.
Click to expand...
My conversation with the dealer went something to this effect:
Dealer: "We didn't screw anything up when we replaced that sensor!! Your TPS has nothing to do with shifting or rough idle. Besides, you had rough idle when you brought it in!!"

Me, readin the invoice: "Customer has LOW idle issue...do not address"

Dealer: "However, if you would like to schedule an appointment, we will gladly diagnose and repair your problem."

Me: "How much is this going to cost me??"

Dealer: "$88 for diagnosis, if the problem turns out to be a faulty TPS, we will replace that for free."

Me: "You're seriously going to charge me $88 so your computers can tell you what I just told you?? The damn thing ran just fine when I brought it in, your techs were laughing at me because I could barely keep it running long enough to get it out of the parking lot!!"

Dealer: "$88 for dia..."

Me: "This is a WARRANTY on a RECALLED part!! Why am I going to have to pay for your mechanic's mistake in installing this part??"

Dealer: CLICK!!




I then sent out an email to the manager and owner of the dealer, but haven't recieved any reply. Also called Jeep corporation....but spent 45 minutes in their "automated phone system", left 2 messages, 2 emails, and have gotten no response yet. Guaranteed reply within 24 hours, tho!! (They've got about 10 minutes left to call me.......)
 
That's a pretty poor response from the dealer. I would go back to them, and point out in no uncertain terms that on a Renix system, the throttle position sensor has everything to do with shifting and that if they were unaware that it also needs to be adjusted with a precision voltmeter then they owe you the adjustment as part of the job, and the diagnosis as well.
 
Matthew Currie said:
To save on search time, I have this one always on hand:


My guess is that they did not adjust it at all, if they have no "Renix mechanics" left around. The Renix engine computer does not learn anything. Driving around will not make a bad adjustment better. On Automatics, the TPS has two sections, one of which controls the transmission and one the engine, so shifting issues from a misadjusted or defective one are not surprising. Make sure you use the correct procedure for yours, and adjust it using the tranny section, not the engine section.
Click to expand...
I am going to start calling this a Renix Myth: "The Renix engine computer does not learn anything."

My own recent experience, tests and my Renix FSM says the Renix does relearn and does store some limited sensor data that it uses. It just does not store codes and does not throw codes. I have posted extensively on this here recently and I have experimented with it extensively and it turns out that starting and running the engine (and transmision... by driving) for a few minutes, then shutting down and doing this routine three times does the trick for the Renix as far as "relearning" goes and it settles down to a normal routine after the 3rd time around. This should be done after replacing a sensor or calibrating a sensor like the TPS. Disconecting the battery does not help.

You may have several problems, first and formost is to pull and clean every single ground wire connection under the hood, battery, engine (2) and firewall (2). Then and only then recalibrate the idle position of the TPS to read 0.80 to 0.82 volts between pin B and pin C with the power on and the engine off, do not start it. Be sure and use pin B and C of the three pin connector, not the four pin connector.

Then go through the routine of driving and parking it (turn the enigne off for 10 seconds before restarting) three times. If you still have ilde problems after that check for vacuum leaks (they casue high idles) or for a low idle remove, clean (very gently, see threads with warnings and how toos) the IAC next to the TPS. You might even remove and clean the throttle body itself with carburator cleaner, but do not get the TPS wet with anything. Water ruins them for sure. Oh, and check the air filter too for a low idle!

The TPS problem and poor grounds can cause the transmission shifting problems and idle problems. The TPS has a second, 4 pin, connection that is attached to the transmission which is electronically controlled partly by the TPS.

If you are going to deal with a stealership, you need to take lots of patience and determination with you, lots of money (a money tree would help) and LOTS of vaseline or KW jelly! Oh, and don't forget a crying towel too!

Lastly, a high rev on start up, lasting for a several seconds seems to be normal for the Renix.

Lastly, some of your problems could be caused by the 3 pin harness connector being attached to the TPS connector backwards. Ask me how I know???? I dare you! Make sure pin A is attached to pin A, and pin C to pin C. The connectors look backwards in a way when connected properly. The ears were gone on mine that normally allow it be connected only one way. I wrote a detailed thread on this, just search "throttle possition sensor idle" and "Ecomike" as poster under advanced search tools. Anyway the ABC is displayed on opposing sides when it is connected correctly. If they are on the same side pin A ends up plugged into pin C. Its just one of those weird oddities.

Oh, and a loose pin, or connection in the wiring harness connectors that attach to the TPS can give you headaches, not to mention idle problems, they can be tightened up with tiny needle nose pliers by tightening up the female pins.
 
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OK. I cleaned and re-seated all grounds I could find. Had to re-locate the groundstrap (block to firewall), moved it so it's now intake-manifold-heat-shield thingy -> firewall. (Extensively checked it, it's a good ground point) After this, I had *extremely* bad problems with idle/misfires/stalling when in Park. After the motor warmed up, and a few restart cycles, it seemed to smooth out a great deal.


Here's the kicker, tho. When the stealership changed the TPS, they stripped out the bottom screw. How do I replace that??







BTW....just an FYI. Diamler-Chrysler Jeep corporation "is not responsible for business practices and/or workmanship of their dealerships". What a load of BS
 
RaccoonJoe said:
OK. I cleaned and re-seated all grounds I could find. Had to re-locate the groundstrap (block to firewall), moved it so it's now intake-manifold-heat-shield thingy -> firewall. (Extensively checked it, it's a good ground point) After this, I had *extremely* bad problems with idle/misfires/stalling when in Park. After the motor warmed up, and a few restart cycles, it seemed to smooth out a great deal.


Here's the kicker, tho. When the stealership changed the TPS, they stripped out the bottom screw. How do I replace that??

You need to check (test) that the intake manifold and the engine block both have the same ground potetnial to each other and to the negative post on the battery. Normally both grounds on the engine are directly to the engine block. Intake manifold may not be grounded to the engine block well enough. If there is more than 1 ohm of resistance from the firewall to the engine block or battery ground, or engine to the battery ground you still have a ground problem.

Which treads did they strip, male or female? Junk yard or dealer for replacement. Female thread is in the throttle body I think.

Sounds like you got the same resuslts I did, further confirming that Renix does store and use some recent historic sensor data that clears out after apx 3 start - run - stop - engine restarts. The AW4 computer also has a relearn period after the TPS sensor is changed.







BTW....just an FYI. Diamler-Chrysler Jeep corporation "is not responsible for business practices and/or workmanship of their dealerships". What a load of BS
Click to expand...
 
RaccoonJoe said:
OK. I cleaned and re-seated all grounds I could find. Had to re-locate the groundstrap (block to firewall), moved it so it's now intake-manifold-heat-shield thingy -> firewall. (Extensively checked it, it's a good ground point) After this, I had *extremely* bad problems with idle/misfires/stalling when in Park. After the motor warmed up, and a few restart cycles, it seemed to smooth out a great deal.


Here's the kicker, tho. When the stealership changed the TPS, they stripped out the bottom screw. How do I replace that??

If they stripped it but didn't shear it off, you can probably get a US coarse thread tap just a little bigger than the original screw, and retap it for that. I did this on my 87 years ago, but don't remember what size I used. Stick to coarse thread which is easier to cut and need not go to full thread depth to have enough grip for this job. Just be careful not to break the tap! Back it up two or three times per turn to break the chip as you go in.

It is a really good idea to have both screws in, since the TPS adjustment is made by loosening them and moving the assembly around. I really think it's time to speak with someone in authority at that dealership to see if they can make good on this botch.







BTW....just an FYI. Diamler-Chrysler Jeep corporation "is not responsible for business practices and/or workmanship of their dealerships". What a load of BS
Click to expand...
 
For some reason it's not putting my text in when I use quote. Let's see if it does for a regular reply.

You can retap the hole, if they didn't shear it off, with a coarse US thread tap a tiny bit larger than the original. Stick with coarse, which doesn't need full thread depth to hold well enough for this job, and remember to back up the tap two or three times per turn to avoid breakage.
 
Matthew Currie said:
For some reason it's not putting my text in when I use quote. Let's see if it does for a regular reply.

You can retap the hole, if they didn't shear it off, with a coarse US thread tap a tiny bit larger than the original. Stick with coarse, which doesn't need full thread depth to hold well enough for this job, and remember to back up the tap two or three times per turn to avoid breakage.
Click to expand...


FYI...it was posting your text, you just were still inside the quote. I went to Daimler/Chrysler/Jeep corporation, they told me that they are "not responsible for workmanship/business practices of the dealers". What a crock of BS. Guess it's time to go looking for the owner of the dealership....Maybe I can have them pay a mechanic's invoice.....

On the other hand, I am going to try and tap that hole out tonight. The screw isn't sheared off, just the head is rounded. Damn those aluminum screws and the torx bits.....I'm just a little worried about tapping that aluminum throttle body....
 
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