Hello.

I am seeking a definitive answer on just how to test my TPS sensor. I have a 90 auto 4wd cherokee with the 4.0 and the RENIX system. The TPS is adjustable. There are two sets of wires coming off this pot, one rectangular 3 way set and one square 4 way set.

I have read many good articles on this, and downloaded a few pdf files. However, there are some things that don't jive.

So, can anyone tell me, do I use the 3plug for "engine related issues" or use the 4plug one? This is stalling/idling related not transmission.

Do I need to see 5 volts or is 4.66 a normal range to start with, understanding I need to find either .83 % of that or .17 % - depending on which plug I reference to. And I have seen both percentages used for both connectors, so lots of confusion there too.

Does the connector I test need to be "connected" or can it be "disconnected"?

I don't have a problem doing the test, its easy. But man, there are sure a lot of different methods given out.

Thanks to anyone who knows what the real deal is.

 

Your gonna have to wait for cruiser or find him and send him a message

 

If he's the man, then I have seen his info already, in multiple places. The problem was other articles/directions did not give the same instructions.

I'll work on some things for awhile and see if anyone else chimes in.

Thanks for the reply!

 

I went ahead and used the data given by cruiser (I think).

Originally I followed an article that said to use (on 90 automatic) the 4pin square connector. Measured input voltage (4.66) and adjusted the TPS until the output voltage / input voltage equaled .815 to .830volt.

I read articles that stated to unplug the connection which made no sense to me, so I left mine plugged in. I read articles that said on manual to use the 3pin and auto to use the 4pin, and some that said to always use the 3pin for any "engine issues" and the 4pin only for "transmission issues".

I went with the 3pin to take readings from. I got 4.88v out of my reference and adjusted the TPS to read .88 with throttle plate fully closed. .8 was the recommended value, but one article stated to use (if I remember correctly) a value that was 16% of the reference, so I adjusted it a slight bit.

I was adjusting this because after I had my head redone and got it all back together, it stalls on me when I slow down. Can slow down in neutral or in gear, fast or slow, from a fast speed or slow speed. Have to put it in neutral and slightly rev it to keep it running. Some googling led me to cleaning the IPC (was very dirty) and adjusting the TPS along with giving the throttle body a good cleaning as well.

Now I have a clean IPC which does work at least to some degree as there is a difference if I unplug it, and a TPS which works and "might" be adjusted correctly and hopefully is within specs voltage wise to operate properly. I opened the plate up and noted that the TPS (basically a pot) had good graduations of readings (as good as can be expected when a hand is doing the plate actuation anyway).

My problem still exists however. Going to try ground next and then battery. I used a propane torch to test for vacuum leaks. Never done that but its supposed to cause increased RPM if its picked up and taken into the cylnders and combusted. Could me the MAP as well I guess or the EGR. Pulled a leg off the EGR solenoid? or relay? and it killed the motor pretty fast. May also have to check the fuel filter and the fuel pressure regulator although my experience with fuel is that its more noticable on demand if there is not enough. Since the issue doesn't happen when braking always, didn't figure it was a master cylinder vacuum deal.

But, good to learn a few things new I guess.

EDIT: forgot to mention got new injectors too and everything is pretty clean after the head job. Gas might be an issue though, its about 6 months old. Did drop some seafoam in for good measure.

 

Yes, you "back probe" the flat three wire connector with it plugged in.

Cruiser's link is right on top if you click on my signature.

The IAC, Idle air control will just stop wherever it happens to be when you unplug it.

I'd take 5 minutes to check my sensor ground resistance and my CPS if I were in your shoes! (staling is one of the things a weak CPS will do)

 

Thanks for the info.

I had seen cruisers nice tips before. I went ahead and did what he suggested on the grounds. Actually mine were in decent shape, only a very slight varnishing on the surfaces. But I used 280grit sandpaper on them anyway to buff them up.

That did not help the issues. I will investigate the CPS tomorrow and see what about it.

Listening to it more closely tonight, it starts up cold and idles at approx 800rpm. It then stumbles for a minute or so, say down in the 550rpm range. There is a noticable "lope" to it, like a gnarly cam in a muscle car, only not in a good way.

The motor would sound like "bla bla bla bla bla bla BLA BLA BLA bl bl bla bla bla bla bla bla bla" when it drops in RPM and more like "bla BLA BLA bla bla BLA bla BLA BLA bla bla BLA" when it is at 800rpm. Actually saying that out loud really does mimic the sound I am hearing too

I'll put some premium in it later this week and see if the new gas makes a difference. I am also going to get it a new battery as the one I have is almost 4 years old and since I don't drive this car except for hunting and snow storms, it has degraded a good bit.

Thanks again for the tips!

 

Well...a little "choppy" but check this link. My idle would cycle. When I changed my 02 sensor it quit that. > https://www.cherokeeforum.com/f2/ren...ce-rms-133153/

 

If I understand this correct, the O2 sensor is a variable resistor? The amount of O2 detected (or not detected) causes the R value to change, thus affecting the output? And a digital meter cannot show this swing?

I'd better find an analog meter somewhere. You're right, that is a bit "choppy", kind of all over the place with information lol. But I think I can manage to figure out the test method.

The link you gave to the OP you got your info from made me laugh. He says lots of things could cause the poor O2 sensor to not behave, such as exhaust leaks, compression, coil, etc etc. Is there a RENIX type cherokee that doesn't have some or all of those I wonder?

I've tried to narrow things down. I know my plugs are new and gapped, my wires are new. My cap/rotor is not but I doubt its out of alignment. The rotor might be somewhat worn, but I haven't put more than 10k on it I doubt.

I have new injectors, but not remans. New head gasket and head job (valve train worked over, head milled) and all the gaskets to go along with that. Allthe sensors are old though, maybe not original though as I used to have a guy do this sort of thing for me.

This isn't my chevy 350 any more (sadly) so I have to learn about all these electronic issues (which is why I always had someone else do it). But having messed with electronics for many years now, its not as confusing as it once was. Besides that, one of the few legitimate uses for having the internet is to gather information, and for things like this its invaluable.

I'll see what I can kick up with the O2 sensor after putting some new fuel in it and getting a new battery.

One thing I haven't seen yet (or I missed) is how I can take a measurement of my ground. I've seen it mentioned, I think.

Thanks for chipping in!

 

The answer is: You use the flat 3 wire connector method and values for engine issues on both manual and auto trans vehicles and the square 4 wire method and values for trans issues on an auto trans equipped vehicle:

RENIX TPS ADJUSTMENT
Before attempting to adjust your TPS be sure the throttle body has been recently cleaned. It's especially important that the edges of the throttle butterfly are free of any carbon build-up.
IMPORTANT NOTE: With the Key OFF, and using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS. The letters are embossed on the connector itself. Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it parallels the valve cover and also over near the MAP sensor on the firewall. If you see more than 1 ohm of resistance, or fluctuation in your ohms reading, some modifications to the sensor ground harness will be necessary. The harness repair must be performed before proceeding. I can provide an instruction sheet for that if needed.
MANUAL TRANSMISSION:
RENIX manual transmission equipped XJs have only a flat three-wire TPS mounted on the throttle body and it provides data input to the ECU. It has three wires in the connector and they're clearly embossed with the letters A, B, and C. Wire "A" is positive. Wire "B" is ground. Key ON, measure voltage from "A" positive to "B" ground by back-probing the connectors. Note the voltage reading--this is your REFERENCE voltage. Key ON, back-probe the connector at wires "B" and "C". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For example: 4.82 volts X .17=.82 volts. Loosen both T-20 Torx screws attaching the TPS to the throttle body and rotate the TPS until you
have achieved your desired output voltage. Tighten the screws carefully while watching to see that your output voltage remains where it is supposed to be. If you can't achieve the correct output voltage, replace the TPS and start over.
Sometimes, after adjusting your TPS the way outlined above, you may experience a high idle upon starting. If that happens, shut the engine off and reconnect your probes to B and C. Start the engine and while watching your meter, turn the TPS clockwise until the idle drops to normal and then rotate it back counterclockwise to your desired output voltage.
AUTOMATIC TRANSMISSION: RENIX automatic transmission equipped XJs have a TPS with two connectors. There is a flat three-wire connector, same as the manual transmission vehicles have, and it is tested the same as the manual transmission equipped vehicles, as outlined above—FOR ALL ENGINE MANAGEMENT RELATED ISSUES.
However, the automatic TPS also has a square four-wire connector, clearly embossed with the letters A,B,C, and D. It only uses three wires and provides information to the Transmission Control Module. THIS SQUARE FOUR WIRE CONNECTOR IS USED FOR TRANSMISSION/SHIFTING RELATED ISSUES ONLY. Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your REFERENCE voltage. Back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage. For example 4.8 volts X .83=3.98 volts. Adjust the TPS until you have achieved this percentage. If you can't, replace the TPS and start over. So, if you have an automatic equipped XJ your TPS has two sides--one side feeds the ECU, and the other side feeds the TCU.
FOR AUTOMATIC TRANSMISSION RELATED ISSUES: Check the square four-wire connector side of the TPS.
If you have ENGINE ISSUES check the flat three-wire connector side of the TPS.
For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced.
Revised 09-22-2012

 

Thank you for that Cruiser. As I said, I've seen multiple ways mentioned and no way to know which was the correct way. As per advice here I used the way you mention. However, in the info you just gave me I did not do the ground test first, so I will do that tonight.

I cleaned my grounds last night, which after running it for a bit has marginally helped the idle. It might have kept an extra 50rpm on it so it doesn't quite want to stall like it was, but it still cycles. I will do the TPS adjustment again. If the ground did have a slight fault I should imagine the voltages are different now.

Its funny how ghosts appear. I've had this jeep since 98. It only had 80k on it and was in very nice shape. I drove it every day for years with only common maintainance needed. Now it has 188k on it and the head gasket went out so I thought why not sink a little money into it and have a fairly dependable backup rig again. Wouldn't you know that once you disturb things all hell breaks loose.

Makes me wonder how the thing ran so well for the last few years

 

They're quite forgiving actually. But when you get evrything right in teh ground and sensor department, they're downright nice!!

Do the senso ground test first.

Then, post up what yo ufind. There is a fix for it. After that, adjust the engine side of the TPS.

 

I checked the ground according to your directions, and had 0 across the board. Double checked and triple checked, nothing. Took readings on the TPS again, and solid 4.88v. Took the connector apart and do have 5.01v on the input, so the TPS is giving some slight resistance with the throttle plate closed. I was thinking I might follow an instruction on how to set the "throttle plate set screw" just to know it was where it should be, but honestly its pretty darn good looking where its at. I can't imagine I would gain much at all.

After a good number of "key cycles" it is running better. I did read that the RENIX has no memory for keycodes etc, but that it does have a memory of about 15 key-cycles. Don't know if thats accurate or not, but after leaving the battery off for 12 hours and cycling it (starting/stopping) many times, the cycling of the low/high idle "seems" to be gone, and it seems to be idling smoothly.

I'll take it out next week hunting and see if some fresh fuel, a new battery and what I've done so far are just temporary or not.

Thanks for the help. I'll post back and tell what happened and how it ran. It will get a good workout in the mountains here (montana). Hopefully nothing goes wrong, as its a long walk to a main road lol.

 

You're probably good to go.

 

Well yes, close as I understand. Actually there is no output whatsoever, just the variable ground. The ECU judges the 02 concentration from that. Besides finding an analogue meter I might suggest you just check the ECU feed, the heater power and the ground. If the idle speed still cycles every 20 sec's or so maybe just change it if you don't know its' history. I'm sure you know it's crucial for milage. They DO go bad. I probably already made my $65 back!

No, Renix has no memory. Save the wear on your ignition switch! Just trust that Cruiser has the TPS test correct. He was a teck on the floor at Jeep for years.....He can do anything except post his IAT resistance.

I walked 60 miles in Montana once. Killed/ate a bunch of fish while I was at it. Glacier Rocks! If you don't report back we will send help in the spring.

 

No need to send out a search party lol. Made it back, but without any game in tow. But thats okay, its not about shooting something so much as just going for a few days.

Progress report on the jeep is good. The cleaning of the IAC and the throttle body and the positioning of the TPS using the 3wire plug, and the cleaning of the grounds, have the jeep running really well. No more loping idle, or high/low idle. Even the intermittent super high idle on start is gone.

I ran it up some good terrain (ie. long steep roads) and did not burn any rings up, which I was concerned with since I did a full head job on a motor with 188k on it. Didn't push it too hard, but it seemed to run fine.

The bad news is that it still over-heats. In days gone by, the temp guage would sit at roughly the 190 mark (just left of center). A few years ago the expansion tank/bottle sprung a leak in the bottom where the fluid leaves it. The dealership wanted over $100 for the bottle and cap, so naturally I bought one from Napa for like $40. The cap never sealed right, so I bought another, which also did not seal right. Eventually I bought an OEM cap, which sealed better.

So what is happening now is that on uphill or otherwise low speed higher rpm rates, the temp gets to about 210 or so, and then starts to boil, which leads me to believe its not pressurized. Its a 50/50 solution of anitfreeze.

Further, if its say at 190ish and I shut it off, about 5 seconds later you can hear it boiling, assuming in the water jacket around the cylinders. Maybe 20 seconds later it stops.

Again, it leads me to believe if the system is not pressurized, the boiling point is not raised like it should be, and at 212 it boils. Not a problem running down the highway at all, only around town or in the woods going uphill.

Now before I go buy a really over-priced puke tank (or whatever it is technically called), am I missing something here? It of course has nothing to do likely with the topic if this thread, but there are so many similar threads out there on cooling that don't already have my specific info I've given, it may be easier just to approach this here.

My options I am mulling over right now are to have a local guy build me a small tank out of metal that will be airtight. I've seen references to getting rid of the OEM system, but don't really want to pay a super high price just now and also don't have time to mod a bunch of stuff to get a real radiator.

Also, didn't I see mention somewhere that you could use a different sensor so the electric fan would come on sooner? I wonder if it even comes on at all, as I cannot hear it. I've even thought about a manual switch for that, but that really doesn't fix the problem.

Any thoughts?