Calling Renix Idle guys

I posted in the Renix files first. I read all I can about the sensors i'm still having problems.

I'm having a problem and am calling all Renix owners. I swapped TB's with my 90 renix. My shift pattern went back to normal. I took my Jeep to a friends garage to help me read and adjust anything that needed it because I still had highs and lows for an idle. We plugged in a scanner and got nothing for the throttle %. The tps isn't showing any voltage. I cleaned all my ground connections prior to this also. He printed out some computer diagrams and such and said that It seems C7 off the computer isn't sending any power to the TPS. Should I be swapping my computer also? My jeep is riding like a dog only maxing out at around 2,500 rpms and shifting no matter what. I can't get a reading out of the tps.

Where did you get the TB from? You said your shift pattern went back to normal. Where you having only shift problems or were there other reasons to swap the TB?

Did you reuse your original TPS?

My original TPS I figure was bad since I had no shift and no voltage. I swapped TB's with a Donor XJ of mine since it ran alot better. The shifting went back to normal but still no power to the TPS. I didn't reuse my TPS. When I say it went back to normal I mean it's driveable now but very sluggish. I still can't get a reading off my TPS. Does anyone know of any fuseable links? Maybe It's between the ECU and TPS? I have a Donor ECU but I'd like to check all possibilities before swapping over. Or should I start with the other computer and work from there.

I know with my '88, if you wait too long during voltage testing (several minutes) the ECU shuts down the 5v supply.....
then you must turn the key off and back to run
unless of course you are testing with engine running

What year was your donor? Are they both auto trans? Do you still have the old TB and TPS?

I always have problems getting a good connection when backprobing the TPS connector because of the seal. I use long brads then clip on the brad end.

I don't know of any fuseable links. I'll check through my FSM.

looks like c15 is the supply to the TPS for ECU. c7 is the output of the tps for ECU input, variable with throttle.
You do have two part TPS after swap right? dumb question...
and - just recently dug up from another post how when the tabs on the TPS connectors get broken, worn, etc.. you can plug things in backwards...

Okay I went to check my other TPS. I'm getting a 5V reading. I havent been able to test drive it because im doing brakes and brake lines today. I pulled schematics off a computer program called alldatapro. It doesn't appear that the TPS has any relays or fuseable links. I think the TPS off the other throttle body was actually bad. I am getting an idle of 1k. I'm afraid im still going to have problems with stalling once in drive now.

Can anyone tell me if there is a wire harness on the firewall that I could check that would have any effect on the tps voltage? A guy from Advance Auto has apparently been working on his renix for awhile and had to clean something back there? I have no idea what he is talking about. It's not the MAP sensor or the grounds.

OverTheHillsATTW said:

Can anyone tell me if there is a wire harness on the firewall that I could check that would have any effect on the tps voltage? A guy from Advance Auto has apparently been working on his renix for awhile and had to clean something back there? I have no idea what he is talking about. It's not the MAP sensor or the grounds.

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He is probably talking about the bulkhead connector on the firewall, it's on the driver's side near the booster. Take out the bolt, pull it apart and clean it, a nylon brush with some electrical parts cleaner works well, after it dries use some dielectric grease and put it back together.

That would be this one.

Thanks alot guys! Appreciate the picture.

I just went outside to check and... I don't have that at all. Is it the same thing under the windshield washer fluid container? Just got off the phone with the guy. I'm going to use CRC electronic cleaner on everything under the hood and CRC Electronic grease everything.

Saudade said:

That would be this one.

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My God, good man-- put some dirt on that thing! Nobody will know what they are looking at if it's THAT clean!!

Seriously, that's got to be the cleanest engine bay/ firewall I've seen on a Jeep in ages:thumbup::thumbup::thumbup:

What's the issue? No 5v at the TPS harness? The test for voltage must be done within five minutes of turning the key ON or the computer shuts off voltage to the TPS.

Are you backprobing correctly? Unplug it and touch the leads to the pins, do you have it now?

I've got a 5V reading now after swapping back to my old TPS. Idle is a little rough still. I'm on jack stands right now so all I can do is idle. Looking at testing her out tomarrow. Considering I have no brake problems.

Shorty said:

My God, good man-- put some dirt on that thing! Nobody will know what they are looking at if it's THAT clean!!

Seriously, that's got to be the cleanest engine bay/ firewall I've seen on a Jeep in ages:thumbup::thumbup::thumbup:

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lol... Thanks. It's just "Dad's Taxi" so it never sees any mud. I hose off the insides once a month as well.

Saudade said:

That would be this one.

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What year is that from? My 89 Firewall connector is ALOT different. Its a two-piece connector that's located underneath the brake booster. Cleaning it was a real PIA. If I were to do it again, I wouldn't unless I had problems.

The bulkhead connector in that photo was not used on his year model, 90. The other bulkhead connector for Renix is the Fuse box connector under the brake booster.

Ecomike said:

The bulkhead connector in that photo was not used on his year model, 90. The other bulkhead connector for Renix is the Fuse box connector under the brake booster.

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Uh oh..........my 1987 has one that looks like that one. It's located under the hood above the brake master cylinder.

Try setting up your TPS leads like this, a few small cuts through the insulation with an exacto knife. Back pinning is iffy and often messes up the seal rings anyway. A little dab of silicon and you can seal up the wires again.



I had TPS gremlins, sometimes there just isn't any shortcuts. Test your TPS grounds to chassis ground with an ohm meter. This can tell you how much resistance is in the TPS ground circuits.
Remember the 5 volts for one half of the TPS comes from the ECU and the five volts for the other half from the TCU.
The TCU ground has a little built in resistance at the TCU.

The TPS harness goes through the firewall to the ECU and again through another grommeted hole to the TCU and has nothing to do with the bulkhead connectors.
Your 89 has no C-101 connector does it?

You may have to ohm test every wire from the TPS to the ECU and TCU connectors. Have someone shake the harness while your doing the ohm test.

The only real way to test the harness is using a system and not cutting any corners. Start from one end and test to the other or from the middle to both ends.

I finally had to cut through the tape on my harness until I exposed all the splice crimps. Found one that was loose, which finally solved all my problems. The resistance would change when the harness moved, sitting in the driveway it was just fine.

The five volt (ECU) circuit isn't only for the TPS, it supplies five volts to many sensors, the MAP included.

Be careful what you are spraying on the sensor connectors. Some of the signals are less than 1 volt and most anything that leaves a coating can mess with the signal. I use a quality contact cleaner, some very small scrub brushes and leave the sensor connectors dry, with no protection and clean the oxidation off once or twice a year.

When I first started testing my TPS connections the first thing I found was a resistance in the tranny TPS connector, which turned out to be WD-40. My next big discovery was the power in was switched around between the three plug connector and the four plug connector. My ECU was powering my TCU circuit and vice versa. The next was TPS ground circuit resistance in bothe circuits and finally a seriously bad splice.
On my 87, many years ago, I found several wires that were fatigued through under the insulation where the injector harness makes the bend at the firewall. Informed Jeep and they put out a TSB, recommending this area be checked periodically.

You almost have to exclude vacuum leaks when trying to chase down an idle problem. The Renix will try to adjust for the extra air and odd things happen. The idle doesn't necessarily go up with a vacuum leak, but may run rich and the idle will hunt (sometimes a little low sometimes a little high). Check your intake/exhaust bolts. Plug off every vacuum line at the intake but the MAP.