Really hi idle!?!?

[Boots]

Every once in a while when I would start the mj to go to school the engine would rev up to around 2000 rpm. It would always go down after a second or two. It's been doing it more and more offer. Today I started it and it reved up to 3500 rpm and wouldn't go down until I unplugged the TPS while it was running. On the way to school it idled at about 1000, it normaly idles at 500. When I started it up to go home it went right up to 3500 rpm and stayed there. By the time I got home it was at 4000rpm. I Shut it down while I opened up the shop and stuff. This time it wouldn't start. I messed with it CPS (not TPS) wires and it fired right up. But still idled at around 3500 rpm. I unplugged the TPS and the idle dropped to normal, I repeated this a few times. I let it sit for a few minutes while I dug out the instructing for testing and adjusting the TPS. I tested the TPS with the ignition off and it was right on, I started it up and now it's running fine. I shut it down and started it a bunch of times and it's idling fine every time now. Anybody got any ideas? I want to get this resolved today because I know it's going to do it again in the morning.

 

Yes I have cleaned the IAC. :wrench:

 

Thanks

Chad

[Comanchero87]

When you say key off. Were you testing the resistance or the voltage? If the resistance is more than 1ohm your readings of voltage will not matter. The voltage is tested with the key on ignition off. Did you clean the butterfly in the throttle body before testing? you clean the IAC port when you cleaned the IAC?

Could be a bad IAC.

[Boots]

The key was in the ON position with the motor not running. I tested the input voltage and output voltage of the TPS. They were with in specs according to the FSM. I cleaned the IAC, the hole the IAC goes into, and had the rubber tube off the throttle body and the butterfly looked fine. All over the weekend. I don't understand how it will happen every time until I try to fix it and all of the sudden it's normal again. Could the CPS some how be causing this? Occasionally I have to mess with the wires to get it to start, not verry often though. When I swapped in the NV3550 I had to fix the CPS because one of wires was loose or something, can't remember exactly.

:wrench:

 

Thanks

Chad

[cruiser54]

It depends which side of the TPS you checked. Did you use instructions that use the flat connector or the square connector. The problem is the TPS has two distinct sides to it. One can be bad, like the engine side, but you're testing the trans side. That's why I wrote the following instructions.

 

CPS will not cause a high idle.

 

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: Set your meter to measure Ohms. 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 runs parallel to the valve cover and also near the MAP sensor mounted on the firewall. If you have an 87 or 88 with the C101 connector mounted on the firewall above the brake booster, wiggle it, too.

 

If you see more than 1 ohm of resistance, and/or fluctuating 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 flat 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 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.

 

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.

 

Revised 03-13-2012

[Boots]

Mine is a manual and only has the flat three wire plug. I will try checking the resistance in the ground wiring right now.

 

Thanks

Chad

[ComancheKid45]

Also check your manifold bolts. ;)

[cruiser54]

Mine is a manual and only has the flat three wire plug. I will try checking the resistance in the ground wiring right now.

 

Thanks

Chad

 

Still got the C101 connector on the firewall?

 

BTW, I got one of the worst sunburns in my life on that beach......

[Boots]

The resistance was .5 ohms. When I wiggled the harness it went down to .4 a couple times. The ground cable on the battery was kinda loose so i tightened that. I'll try checking the manifold bolts too. Ya it still has the c101 connector but ive cleaned it super good like three times.

 

Thanks

Chad

 

Which beach are you referring to?

[Boots]

The manifold bolts were good. But my distributor is squeaking, does that mean its time to replace it?

[flint54]

RE: Distributor squeaking.

Remove distributor (after marking position), remove roll pin securing

the gear, remove cap, rotor, and sync plate. then slide out the

shaft. Chances are there's old gummed up oil causing the squeak.

That was the case with mine. Might clean it up and be nearly good

as new, but at least no more squeak.

[cruiser54]

The resistance was .5 ohms. When I wiggled the harness it went down to .4 a couple times. The ground cable on the battery was kinda loose so i tightened that. I'll try checking the manifold bolts too. Ya it still has the c101 connector but ive cleaned it super good like three times.

 

Thanks

Chad

 

Which beach are you referring to?

 

Aptos, in your avatar.

 

Looks like your sensor ground circuit is good.

[Boots]

I cleaned up the distributor like told above and the squeaking went away. When I first took it out I was barely able to spin it by hand, is was super stiff. I cleaned off the old stuff and put a little grease on the shaft. It seems to be idling pretty good now. Just gotta wait and see how it does in the morning.

 

The picture in my avatar is actually Pismo Beach. I wish you could drive on the beaches in Aptos, but that will never happen. :no:

 

Thanks for all the help

Chad

 

[Comanchero87]

Pismo....ahhh the memories. I grew up in Paso. In those days I was rockin the 78 K5 with an impala 327 and muncie 4spd. That thing was a beast. Gas was like 2bucks a gallon though.

[cruiser54]

Pismo....ahhh the memories. I grew up in Paso. In those days I was rockin the 78 K5 with an impala 327 and muncie 4spd. That thing was a beast. Gas was like 2bucks a gallon though.

 

Remember Pismo, too. 67 Bronco with a built 351W and a 4 speed, 4.11 gears, running Gates Commando tires.

Gas was 29 cents a gallon.

[Boots]

The MJ seems to be running pretty good. No issues what so ever.

 

 

Pismo is really fun. It's about 3.5 hours from were I live, not too bad but still too far for my liking. lol.

 

Thanks

Chad

[Comanchero87]

Comp hill baby. Thats a nice 100yrd long sand dune hill climb if you already dident know. Good fun the freaking Hummer cops are Nazi's though. We went camping there when I was like 18. We brought a keg and cooler full of 6 24pks. As soon as we got there I opened up a beer and the cops swooped in. Made us dump out every single beer and bottle, took the keg, wrote me a MIP and then kicked the whole group out of the park. My friends almost killed me.

[cruiser54]

I was there in the early 70s. Am I dating myself?

[Boots]

So it hasn't done it since the beginning of this week, but was still idling rough. I just replaced the TPS with a brand new one and adjusted it properly. Started it up and the idle went right up again, and stayed there. After a few second I unplugged the TPS and it dropped right downtown normal, then I plugged it back in. It stayed at normal idle speed but was a little rough. I shut it down about a minute later then started it right back up, it started up like it should have. :nuts: I'm going to drive it for a few days and see how it acts, I'm not sure what else to do at this point... It has also been idling rough for a while now, but in the last week or so it has been worse. Sometimes when I come up to a stop sign and let off the gas the rpm continue to go down past were they should. Last night I had to take my sister her spare key. when I backed out of the drive way and made a 270 degree turn all at once and came to a stop, the rpm went all the way down to zero on the tach and it barely came back up to normal after I pressed the throttle. What do you guys think?

 

Thanks

Chad

[cruiser54]

Maybe you got a bum replacement TPS?

 

No high idle with the old TPS anymore but a rough idle, correct?

[Boots]

It seemed to be running better today. No high idle and it seems to have smoothed out.

 

Maybe you got a bum replacement TPS?

 

No high idle with the old TPS anymore but a rough idle, correct?

 

The rough idle always seemed to be there but the high idle was very inconsistent and happened randomly.

 

thanks

Chad

[cruiser54]

So with the new TPS you have a more frequent high idle along with the rough running it has always had?

[Boots]

Sorry for the confusion... The new TPS seems to have fixed it. The rough idle smoothed out a lot, and the high idle seems to have disappeared. The only time it has had the high idle since the new TPS was the first time I started it right after installing it. Since then it has been fine.

 

Thanks

Chad

[cruiser54]

Sounds like you're good to go.