efficientkilla007

I know this thread is on here a million times but I've read them all and tried just about everything. I had took my throttle body off and cleaned it which, by looking at it I thought would make a huge difference but ever since I cleaned it it's been idling at 1500 rpms. It's a manual so it's tolerable but very annoying. I've cleaned the IAC, adjusted the tps, cleaned the throttle body mating surface to make sure there's no leaks there, my map sensor vacuum line is perfectly intact, I've sprayed carb cleaner everywhere and never saw a change in idle. I'm just looking for anymore tips anyone can throw my way. It's a 1990 4.0 renix 5 speed. And if anyone can tell me the tps adjustment procedure for the manuals that would be great, just to make sure I'm doing it right. I've been following the directions for adjusting the tps on automatics, which involves using the square connection, which is useless for me.

tjwalker

If this high idle happened AFTER you removed the throttle body, I'd suspect a vacuum leak on the throttle body, possibly the TB gasket. Double check it. Gotta look at the "cause and effect" principle if it wasn't idling this high before. Be sure that the throttle linkage is clean and is working properly. TPS information below.
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RENIX (87-90) 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: Using one 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 other lead of your meter to the negative battery post.
If you see more than 1 ohm of resistance 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 a three-wire TPS mounted on the throttle body.
This manual transmission vehicle TPS provides data input to the ECU. The manual transmission
TPS 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. Adjust the TPS until you have achieved this percentage. If
you can't achieve the correct output voltage replace the TPS and start over.

AUTOMATIC TRANSMISSION:

RENIX automatic transmission equipped XJs have a TPS with two connectors. There is a three-
wire connector, same as the manual transmission vehicles have, and it is tested the same as the
manual transmission equipped vehicles--FOR ENGINE MANAGEMENT RELATED ISSUES.

However, the automatic TPS also has a four-wire connector clearly embossed with the letters
A,B,C, and D.. For the automatic transmission equipped vehicles the four-wire connector
provides data to the TCU.

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. If you have TRANSMISSION issues check the four-wire
connector side of the TPS. If you have ENGINE issues check the 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.

efficientkilla007

Alright, Im about to jump on that now. I appreciate all the useful info! I'll definitely be keeping that on hand.

chuckanut

I had a high idle problem with my rig. Around the 1500rpm range. Ended up having a bad Exhaust Manifold gasket, found it after it got worse. Fixed that and help ALOT. Still was getting around 1300rpm replaced TPS and Idle Steper Motor, those helped a little. Last thing I did was relocate the Vaccume Canister up under my coolant bottle, that helped a little more right around 1000rpm. Evidently I had a vaccume leak I didnt catch. Goodl Luck!

cruiser54

Be sure to check/adjust on the "engine" side of the TPS in the instructions Mr Walker provided.

efficientkilla007

So I've adjusted the tps, replaced iac vave, never found a vacuum leak and my problem is still there. The only thing I've noticed is if I unplug the ccv hose on the back of the valve cover and plug the hose with my finger the idle drops a little, but not to normal. does anyone have any other suggestions on this?

cruiser54

Is it possible someone turned the allen headed throttle screw to increase the idle at sometime? That butterfly is to be completely closed.

efficientkilla007

Would that be okay to mess with? I know on the back of the firewall where it says my plug gap it says the idle speed needs no adjustment, but would that be good to try? I'll try anything at this point.

cruiser54

No, it's not okay to mess with and maybe somebody did previously?

But, it can be rectified if it was messed with.

Remove the intake boot so you can peer down into the TB. Is the butterfly completely closed? If not, loosen the allen headed screw til it is. Then, turn the screw in til it just touches the tab on the TB lever.

TPS would have to be readjusted BTW.