1988 Jeep Cherokee curbside idle very high

Tiny
JAYANNE
  • MEMBER
  • 1988 JEEP CHEROKEE
  • 4 CYL
  • 4WD
  • MANUAL
  • 240,000 MILES
I just installed a new exhaust manifold and a new o2 sensor. When I started it the idle speed was very high (perhaps 2000 or more rpm). I let it run to operating temp but the idle speed did not and does not slow down. This is a fuel injected throttle body.
I've checked the vacuum hoses, replaced one.
Disconnected the some of the sensors near the carborator with no change.
I can't find a schematic showing the sensor connections to check if I have them all connected correctly.
Jay
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Wednesday, September 1st, 2010 AT 10:50 PM

30 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Did the high idle just start since the manifold was replaced?
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Thursday, September 2nd, 2010 AT 10:38 AM
Tiny
JAYANNE
  • MEMBER
Before I changed the manifold it did idle a little fast but nothing out of what I thought was ordinary but it's been that way for several years now, maybe I just got use to it. When I would come to a stop light the idle would seem a little fast like a hanging throttle cable or something, I would kick the accelorator but that never seemed to affect it. It never did what it's doing now after changing the exhaust manifold and a new O2 sensor.
But this high speed idle is way out of normal and I've lubed the carb linkage and all seems to be working okay. The high speed idle is from start up till I turn off the key.
Thank you. Jay
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Thursday, September 2nd, 2010 AT 11:19 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
The only things I can think of is either a vacuum leak, idle air control valve, or throttle position sensor.
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Thursday, September 2nd, 2010 AT 12:15 PM
Tiny
JAYANNE
  • MEMBER
I am not able to locate the item you name as 'Idle Air Control Valve' but I do have and have located the 'Idle Speed Actuator (ISA), could that be the same thing or should I keep looking for the air control valve?
I have a vacuum gage, what should the vacuum be on this? I'm guessing somewhere above 14 lbs, I haven't check this yet.
Because there is several sensor connector in that wiring around the TPS is it possable I've connected the wrong one? I've tried to find a drawing or something that will tell me how those are to be connected. The O2 sensor and the Idle Speed Actuator I'm pretty sure are connected correctly, the others have two wire connections so it would be fairly easy to get them mixed up (for me anyway)

Is there a way to check if the TPS is working without purchasing a new one?
I'll keep looking for a vacuum leak and change the TPS but this will take me a couple of days and this is already Friday so it's most likely I won't be done with it till Monday.
Thanks again for your help. Jay
PS: I can take a picture of some of the parts around my carb (throttle body) if it would help you to help me.
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Thursday, September 2nd, 2010 AT 11:42 PM
Tiny
JAYANNE
  • MEMBER
I did find that the Idle Speed Motor was not functioning so I replaced it. The Throttle Position Sensor tested out as working okay. I believe the Idle Speed motor did stop the run-away really high idle speed. The idle speed (when cold) is now normal and acceptable but after the engine warms up (like 10 minutes or so) the idle is still too fast. What else might be causing that?
Jay
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Thursday, September 9th, 2010 AT 1:12 PM
Tiny
JAYANNE
  • MEMBER
Right now I'm greatly dissappointed in the almost help I've received. Not one question has been answer, absolutely no followup and other than all this I feel I've been abandon as well. Whoever picked up my case apparently had no idea how to deal with my problem nor did he or she pass me on to someone who does know. For me the twenty bucks I sent for help is a total waste. Thanks a for all the no help.
Jay
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Wednesday, September 15th, 2010 AT 5:05 PM
Tiny
CJ MEDEVAC
  • EXPERT
Mr./Miss/Mrs./Other Jay. Please read my profile and maybe some of my CJ5 & 7 Answers in their forums. Even read some of my other answers that pertain to Cyber-Rigs (such as yours). You will see why my wife and others call me, A/n/a/l

I do not know your plight here, but sometimes it gets really busy--I just play here, I am a member like you. That answers alot more. This is one of my hobbies now.

This site has been really a lifesaver for me.I broke my foot at work, and was "Reclinerized" for a long time.

This site gave me something to do and something to learn.I even pizz people off here too!

The worst thing about being a Cyber-Tech is, WE DO NOT KNOW WHAT YOU, OR YOUR EVIL BUDDY DID TO IT ALREADY. AND EVERYONE IS SCARED TO TELL, OR JUST FORGETS. This really throws in a new twist sometimes!

It's hard enough to explain stuff, while you are looking over their shoulder!

I am not a Backyard Mechanic.I am Better Than That!

I am a Self Certified Rear Lawn Vehicle Technician (SCRLVT) (sorta what you wanna be)

Ever since, even before I had my drivers license, I've strived for Perfection when repairing my, or anyone elses vehicle.'Cause I want to repair once. Not twice. And get the best efficiency at the same time!

Yes, I have pizzed off many people along the way, questioning their answers. But I didn't care. This is "MY STUFF" we are talking about. And It Matters alot to me. No Half-Azzing on my stuff. Or my Mom and Dads. Friends Etc!

My rigs. Have not been in a Pro-Shop, in over 15 years (probably longer than that). But I have, and I get the answers I need. Especially on the Cyber-Stuff (my weakness) I understand the "Mechanicals".I am not up to par on the sensors.I'm used to the Traditional Diagnoses (basically by ear). But the computer stuff CONTRADICTS. The Old Way alot.
Yes, You guessed right.I'm still PIZZING people off. To gain knowledge for myself.I even still find new places to gain my knowledge.I make the system, work for me!

I find the least expensive parts---Even if it means "Part Swapping" to diagnose--Inexpensively from a Salvage Yard. Just to verify the problem. Dependant on the part, I will PURCHASE a new one. Once it is Figgered out.

I do not like working on cars. Especially the new ones.I DO IT OUT OF NECESSITY.I DO NOT "TRUST" OTHERS ON "MY MACHINE"!

I am not rich---I have seen too many HORROR STORIES. Experienced 1st hand, in a company plumbing truck. Joe DUMB-AZZ changing the oil with an IMPACT WRENCH. Saw results on another rig (using the same "quick change oil place") The rubber plug they installed, fell out and my friend, destroyed her engine really fast. They had told her they were installing the plug, at the time (she had no clue. WHY? EXACTLY). But I do."IMPACT MAN. You can do damage with your bare hands too.I see too many, who do not care 'cause "IT AIN'T THEIRS"

So, now down to you.I do not know your rig. But my Dad has a '86 Thunderbird. Close in years to you. So It may have similar systems!

He (we) Had a Idle problem on it. So you know whats I duzz. Crank on the throttle body Idle screw. Wrong! I just totally messed up "BASE IDLE!"

Now I have 2 problems----that are creating even more problems."Base Idle" is the STANDARD THROTTLE SETTING in which everthing is calibrated to (other sensors, thru Mr. Computer). So now other issues arise 'cause stuff ain't "In Sync", and I am pulling my hair out.I was ignorant, and knew no better.I did learn, it does't work like the old stuff!

Tune in tomorrow, with a reply, And I will continue my Novel. Its not too much longer, as to what I learned, and how to overcome it. How to get base Idle right again.

Gotta go help my Pap, go to Doc, having the chemo stuff, is very weak. Traveling 30 miles to get to his house.

Respond

The Medic
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Thursday, September 16th, 2010 AT 9:24 AM
Tiny
JAYANNE
  • MEMBER
Now you make me feel really bad; I'm sorry I came on so strong and I do truely appologize. I'm sorry! I know it's tough to help someone when you have no idea what they have already done. I also understand timing (not engine but circumstances timing) I've been working on my Jeep for a couple of weeks and exhausted all of what I thought I knew and nothing worked. I did follow your suggestion on the Idle Contol Motor as I suspected it quite some time ago but it was $100 bucks and I didn't want to spend that kind of money on a guess. When you suggested it way back on Sept 2, I did follow through and it did prove to be a major part of my problem.
Now my side of the this story: I explained all I had done and the result. I asked several questions and got no reply at all. My car is sitting here doing nothing for me and I'm wiaiting for some kind of direction. I too could only guess at who or what kind of response I'd get, but for three weeks I got no feed back - nothing. So by then I reacted rather than inquire. I'm still sorry about that and I did not expect help through a complete overhaul for $20 bucks but I did expect something. It looks like my premature complaint did, if nothing else, bring about a response, and for that I thank you.
Still working on my Base idle speed which I'm guessing idles somewhere around 12 to 15 hundred R's when I come to a stop. When it's cold, for about 10 minutes it idles just fine. Other than this my Jeep is running very well.
I'm sorry I offended you. Hoping you'll still assist me in some way.
Even though my Idle Position Sensor checked out as working (Auto Zone checked it for me) I was planning to replace it to see if that will slow down my now just fast curbside idle.
Thanks again. Jay
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Friday, September 17th, 2010 AT 1:24 AM
Tiny
CJ MEDEVAC
  • EXPERT
OK JAY, Just so you know.

You have now been dealing with 2 people at this site,

1st Guy. JacobandNicholas (ASE certified mechanic-really knows newer rigs)

2nd Guy, Me, SELF CERTIFIED REAR LAWN VEHICLE TECHNICIAN.I have earned "Helper Status" and I know my CJ Jeeps well.I do understand other vehicles, but I really only answer, if I think its within my capabilities.1ST guy is probably laughing at my ignorance of newer rigs!

I answered you, because I saw you were "Unhappy", to say the least.I thought maybe I could help with some input. Since I had spent so many hours researching the '86 T-Bird (close in years w/ yours, maybe w/same type systems.)

EVERY TIME SOMEONE ANSWERS A POST, ALL INVOLVED GET A AN ALERT, AND YOUR POST COMES TO THE TOP!

So, Jacobandnicholas. Is monitoring this as well, he may be your best bet as far as Computer Rigs go.

Information in detail, is our best friend, as far as helping anyone

. So Do you have throttle body fuel injection?

Have you messed with the idle adjustment?

Have you/ or do you have a THROTTLE POSITIONER (not throttle positioning switch, you'll have that too, maybe) on your body? (I was shown the EZ way to reestablish BASE IDLE, and "Zero In" the positioner again should your system be similar to my Dads, IF NEED-BE for your too.)

Regardless--answer the questions and any other info you can muster.

A Repair manual as mentioned in my profile may aid you in I.D. Ing stuff, and be useful for future SCHEDULED MAINTENECE and Repairs, keep it in your rig. Someone else may be able to use it to help you!

I'M GONNA GIVE THE OTHER GUY (J & N) A CHANCE TO GIVE YOU A BETTER ANSWER THAN I, BUT I WILL COME BACK SHOULD HE NOT RESPOND IN A DAY OR SO.

REMEMBER US IN "FEED BACK" GIVES THE NEXT POOR VICTIM A GLIMPSE OF THEIR ANSWERER!

DON'T GIVE UP ON US YET!

THE MEDIC
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Friday, September 17th, 2010 AT 9:37 AM
Tiny
JAYANNE
  • MEMBER
Thank you for your response, I really do appreciate it.
I do have a Throttle Body with fuel injection. I've been able to determine it has an Idle Speed Motor (I replaced with a new one, at your suggestion. I took the old one apart and it was obviously burnt and one brush was way out of place).
It has a Throttle Position Sensor which I have not replaced yet. My local Auto Zone store had the equipmnet to test it and told me it showed some weekness but it was working okay.
There is and O2 sentor whcih I replaced.
There are three other sensors that look to me like are coming off the Intake manifold which I have not replaced and I can not find a schematic showing me which connector goes to which one and I could have one of these connected to the wrong one. All three of these are two wire and the others (Idle Speed Motor and the O2 sensor are three wire.
No need for you to go back and read the other postings but I did attempt to explain all this earlier to give you an Idea of what I've (me, none else) done so far.
This should come close to catching you up-to-date.
The out of control Idle (upon start ran like I had my foot on the accelerator, way to fast to do any meaningful checking) was fixed with the new Idle Speed Motor.
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Friday, September 17th, 2010 AT 2:27 PM
Tiny
JAYANNE
  • MEMBER
Ooops. One question I did not answer:
No I did not mess with any idle adjustmentsl, there arn't any to mess with.
The new Idle Speed Motor came with a hex head bolt that when screwed all the way down did not slow the runnaway idle any but after I removed it the idle went down to normal but still after warming up remained somewhere around 12 to 15 hundred R's (only a guess), but it's now down to something I can deal with.
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Friday, September 17th, 2010 AT 3:13 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Jayanne,

I am so sorry. I never received a follow up for some reason. I have to thank CJ Medevac for bringing it to my attention. When there is a follow up from a customer, I receive a notification via my email, but this time I never got one. I always respond within one day of receiving notification. Again, sorry about that.

As far as the idle issue, don't replace the throttle position sensor if it was checked and okay. I really think you have a vacuum issue we are dealing with at this point. Have you checked the EGR to make sure it isn't clogged with carbon?

Let me know. (I will keep this in my mail. If I don't hear from you in the next couple days, I'll get back to you.)

Joe
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Sunday, September 19th, 2010 AT 12:05 AM
Tiny
JAYANNE
  • MEMBER
Your delay to my reply was not even noticed on my end. I get notice through my e-mail as well and if I didn't I have no idea how I'd look for an answer on this site. I found this aska question kind of by accident and have not looked around the site much.

Anyway, I did clean the EGR and put a new gasket under it. The diaphram was not sticking so I did put the old one back on.

I have not checked with a gauge what the vacuum is but I've searched for leaks and changed two suspect short hoses.

I intended to get a new TPS Monday cuz that's about all there is left that I can check.

There's three sensors connected to the Intake manifold and if I have them connect to the wrong connector that could cause the on board computer to give some false reading, couldn't it? But on your suggestion I'll keep looking for a vacuum leak.
Thanks. Jay
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Sunday, September 19th, 2010 AT 12:56 AM
Tiny
KHLOW2008
  • EXPERT
Hi Jay,

If the 3 sensors are connected wrongly at the the intake manifold, they can cause the engine to perform erratically.

What are the wire colors for each of the connectors?

Did you try to adjust the ISA?

You mentioned taking pictures of the parts around the throttle body, that should help.
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Sunday, September 19th, 2010 AT 10:25 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
I got this message. Yes, if they were connected in the wrong place it would cause the engine to act irratic.

Here is what I can tell you about the tps. It usually won't have an affect on the base idle but as soon as you hit the gas is when the problem would start. That is what is making me lean toward a vacuum leak. It doesn't have to be a vacuum hose. It could be the actual intake itself, loose throttle body.
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Sunday, September 19th, 2010 AT 12:33 PM
Tiny
JAYANNE
  • MEMBER
Oh my, I answered some question on this reply and sent some pictures then when I hit the preview button I lost the whole thing.
This engine is running to well for it to be the TPS after what you told me about it. I installed a new manifold gasket and one under the throttle body and EGR valve. I would not rule out a leak at these points but there's nothing that indicates they are leaking.
I will send a 5 pictures, this time not to Preview. Just hope you get em. Thanks a whole lot for your help. Jay


http://www.2carpros.com/forum/automotive_pictures/568312_001_2.jpg


http://www.2carpros.com/forum/automotive_pictures/568312_002_2.jpg


http://www.2carpros.com/forum/automotive_pictures/568312_003_2.jpg


http://www.2carpros.com/forum/automotive_pictures/568312_004_2.jpg


http://www.2carpros.com/forum/automotive_pictures/568312_005_2.jpg


http://www.2carpros.com/forum/automotive_pictures/568312_006_2.jpg


http://www.2carpros.com/forum/automotive_pictures/568312_007_2.jpg

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Monday, September 20th, 2010 AT 8:07 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
I checked a schematic and everything looks correct. I hate to say it, but I'm at a loss. If you disconnect the idle speed motor, does that change anything?

FYI: I'm going to ask another tech to look at this and see what he says.

Let me know.

Joe
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Tuesday, September 21st, 2010 AT 11:30 PM
Tiny
CJ MEDEVAC
  • EXPERT
I hate to butt in, Buuuuuuuut,

When I messed up base Idle on my Dad's T-Bird ('86 3.8L) The procedure I was shown to get it back was:

1) Crank up, get to operating temp

2) I Shoved my finger inbetween the Throttle Tab on the Throttle body and the "Throttle Positioner"?

3) When I did that, the "Positioner" Backed up on its own, As I "RODE" it down with my finger.
(It was trying to reduce the RPMs, I created w/ my ONE finger, holding throttle open, and simutaniouly, slight pressure on the Positioner)

4) As soon as it backed all the way up (bottomed itself out), My BUDDY UNPLUGGED IT. Now it was out of the way!

5) Then using my Dwell/ Tach Meter, I adjusted the IDLE SCREW (That I Messed With, in the beginning!)

6) I believe I set The FORD's (Base)Idle to 400 RPM (whatever it was supposed to be, according to our reference)

7) Then we plugged the positioner back in

8) SUPPOSEDLY, as the "Positioner" pushed itself back out, and CONTACTED the "Throttle TAB".

9) When it TOUCHED the tab, It had "ZEROED" itself to the system.(Now calibrated!)

10) Everything seemed, "GOOD TO GO", on Pap's car.

Is this the correct way to do it?

Will it work for Jay?

DO NOT DO THIS, JAY, UNLESS J&N TELLS YOU TO!

The Medic
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Tuesday, September 21st, 2010 AT 11:51 PM
Tiny
RASMATAZ
  • MEMBER
Try dropping the idle speed thru the ISA-plunger


http://www.2carpros.com/forum/automotive_pictures/12900_isa_jeep_1.jpg



Adjustments

This adjustment is only required after the ISA motor has been replaced, and is only used to establish the initial position of the actuator.

NOTE:An ISA Exerciser Tool (Part No. Ele. AB.99) is required to successfully complete the adjustment of the ISA motor. Slight modification to the ISA Exerciser Tool (Part No. Ele. AB.99) connector may be required so that it can be connected to the ISA motor. Use a hobby knife, and cut grooves in the casing of terminal (A) that match the grooves in the terminal casing of terminals (D) and (B).

Disconnect and remove the air inlet bonnet.
Start the engine and allow it to reach normal operating temperature.
Turn air conditioning to OFF position.
Diagnostic Connector Identification


http://www.2carpros.com/forum/automotive_pictures/12900_isa_1.gif



Connect a tachometer across diagnostic connector D1 terminals 1 and 3.
Disconnect the Idle Speed Actuator (ISA) electrical connector from the motor.
Connect the ISA Exerciser Tool (Part No. Ele. AB.99) to the ISA motor.
Using the Exerciser Tool, extend the ISA plunger fully.
Idle Speed Actuator (ISA) Motor Adjustment

Turn the Adjustment screw, while watching the tachometer, until the engine speed is 3500 rpm.
Disconnect and remove the ISA Exerciser Tool (Part No. Ele. AB.99) and connect the ISA electrical connector. Idle speed should return to normal after a few seconds.
Re-install air inlet bonnet.
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Wednesday, September 22nd, 2010 AT 12:03 AM
Tiny
JAYANNE
  • MEMBER
Oh my, you guys have given me plenty to work on some of which I have not done yet.

No. There was no change when I disconnected the 'new' Idle Speed Control Motor.

It will be several days naow before I get thorugh all you've given me to work on. Thanks again. Jay
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Wednesday, September 22nd, 2010 AT 1:47 PM

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