kurama49

Hi guys, Well I'm having another engine related problem with my XJ...

So, a few days ago, me and a friend were driving home in it, and all of a sudden it started sputtering and running really rich, So I kept driving it for a minute like that and it cleared up and went back to normal.... until I got home.

So we got home, shut it off and went in to play xbox for a bit, came back out cranked the jeep over and all of a sudden it shot right to 3,000rpms. and stayed there, I tryed shutting it off and cranking it over a few times more, but it resulted in the same high idle. So I tryed unplugging the TPS, which lowered the RPMS to its normal idle, but had horrible throttle responce, So I plugged it back in, same thing happened 3,000rpm idle.

So me thinking that was the culprit, i went out and bought a new one, [$102...] I put it on today... and it was STILL doing the same thing. I double triple checked that it was adjusted ok and on there tight... So I thought it might be the Idle air control valve?

So, I robbed the Idle air control valve off my parts jeep [a 96 XJ sport with a 4.0L h.o] And installed it, and immediately it went to idling ok, idled smoother, but quite lower, it was idling at around 650-700rpms. Normally it idles at 800-950. So i take it for a test drive, and found out, when the engine was under a load it would have a random miss through the rpm range. so baisically, climb 500rpm die for a quick second, come back, climb another 500rpm, same thing on repeat.

So, I came back home, took the idle air control valve out, made sure it was nice and clean. then put it back in... and low and behold my high idle was back except it was 2,000rpm, and if I apply throttle it revs up ok, but takes forever to idle back down to 2,000rpm

I have a new Idle air control valve on order, but it wont be in until next week.. So any ideas on how to get me through this week?


Oh and I also converted it to a open cooling system using everything off my parts jeep... if that affects anything

trojanchrokee

I just had the same problem, I cleaned the throttle body with carb cleaner and a tooth brush and slapped it back on, cleaned out the Iac and other 2 connections with brake fluid and compressed air, then checked all vacuum lines. I did all that and it was still idling at 2k so I unplugged the battery to reset the comp and once i hooked it back up everything was reset and adjusted and it ran fine. The work only took about an hour too! You might want to start there.

kurama49

I tryed all of this :/ if i reset the computer, it goes back to idling at around 1,000rpm. then when i shut it off and crank it over again, it goes right back to 3,000rpms

cruiser54

$102 for a TPS?

Manual trans?

What percentage of input voltage did you set the output voltage? 17% or 83%

kurama49

The jeep is a manual, but i ordered the automatic one.. the standard one would have been around $186.

How would I set the voltage? I dont have a multi-meter but i can go pick one up. My haynes manual just said baisically put it on and leave it.. didnt mention anything about setting voltage

cruiser54

Here's how to set the TPS:

But I'm gonna make a suggestion here that will help you and cost you a little time and probably no money.

Do this stuff first.

Click on the pink link in my signature. Do #1, 2, 5, and 8.


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

kurama49

Thanks cruiser, Also my jeep has a square plug in to... My old tps didnt have a plug in for it, but the new one does? should i plug it in or leave it unplugged? I think it would be for the shift points if my jeep were a automatic?

cruiser54

Leave it unplugged. It's for the auto trans.

kurama49

Ok, well I just replaced the idle air control valve with a brand new one and.... IT STILL IDLES HIGH.

I reset the computer, started the jeep up, went back to idling perfect, so i left it idle for a little bit, got in it, took it up the road, first noticed that it was still stumbling and dieing under load... So i got to my uncles [which is 3 houses up the road] put it in neutral and it went right to 2500rpm. and stayed there. So, i reset the computer again, it started idling good again, went back down the road [stumble still there] pulled into the driveway, put it in neutral, and it went right to 3000rpm again. So i shut it off, started it again, and it idled at 900rpm. so then i did the same thing over, and it went to 3000rpm... This is aggravating me to the point that I actually put a dent in my door... [I didnt mean to hit it that hard.] But yea.. any input would be great.. And theres no vacuum leaks, But I also noticed that my temp gauge isnt working now..

cruiser54

Did you do the tips I suggested? The computer doesn't really reset. wasting your time there.

kurama49

Ok, so i did all the tips you suggested cruiser, but it still Idles high But i noticed that with the intake tube off, around the little port where the IAC rests, theres a crazy vacuum, So I waved a rag over it and it sucked it in some, but went back to idling like it should.. So I made a little gasket as a experiment to go between the throttle body and intake tube that covered the IAC hole, it idles fine with it, but sputters when going through the gears. Probually because its not getting enough air?

So, a list of what Ive done today:
Cleaned the C101 connector
Throttle body is cleaned to the point of looking like i just bought it.
TPS is new and adjusted properly
IAC is new [dont know if you have to adjust it..]
Ground cables are new
Dipstick stud is cleaned and theres no gunk around it.
I just ordered a new throttle body gasket because i dont know if the one i made is cutting it... but it seems to be holding.
I cant find any vacuum leaks [i did the spray carb cleaner and lisen for a difference in the idle]

So, I dont know what to do now.. Its really frustrating, because i have to have this fix by TOMORROW. I've been planning a road trip to truro for mudfest the past 2 months, but this could burn those plans completely.

cruiser54

Does it stay high?

Did you do the sensor ground test?

je4reyk

Get a good volt,ohm meter and really ,pay close attention to the ohms to ground ,those tips saved me a lot of headaches,when I finally did them

kurama49

Well, when i first start it, it goes to 2500, then creeps up to 3000 and stays there, I did do the sensor ground test, when i wiggled the harness my meter only went to 1ohm of resitance ,

cruiser54

That's good. Does it EVER start and NOT go to higher RPMs?

New TPS?