trouble maintaining an idle - JeepForum.com
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post #1 of 13 Old 07-20-2019, 10:59 AM Thread Starter
cHaB797n
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trouble maintaining an idle

Iím at my wits end on my 96 Cherokee classic. It has trouble maintaining an idle. After removing/cleaning the throttle body and replacing the idle air control valve the engine runs just fine and I can watch the RPM through its operating range and idle at 600 steady when I come to a stop. I can see the computer controlling the idle and everythingís fine. Then the next week something happens. It gets hard to start in the morning. Spark is good but it just doesnít climb into its operating range and if I do manage to get the Cherokee rolling it just stalls out first stop sign. It will act this way until I take the throttle body off again. And so over and over. I have replaced three idle air controllers and most recently the throttle position sensor. So currently it just doesnít want to start and idle. I disconnected the battery to reset the computer but still it doesnít want to start and idle. Good spark so I know itís not the crankshaft position sensor. Right now Iím thinking about the throttle body as the bore is not completely smooth throughout or maybe the computer is it receiving or sending signals correctly. Or maybe if I use a higher grade fuel. But like I said every time I removed the bottle body and clean it or replace parts everything runs fine for a week or two. It holds good fuel pressureholds 50psi,replaced injectors. any ideas? Scott

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post #2 of 13 Old 07-20-2019, 11:42 AM
CJ7-Tim
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Are all the tune-up parts fresh ? Have you tested the coil ?

Are you installing genuine Jeep sensors, or crappy Chinese clone sensors ? Most auto parts stores sell cheap crappy Chinese made parts, some that even come with a "Lifetime Warranty". These parts are poorly manufactured and/or made from inferior materials. They are often out of specification, or even failed, right out of the box. The ones that are not faulty many times will have a short service life before they fail. Always buy top quality replacement parts and genuine Jeep engine sensors. Numerous threads detail long and frustrating searches for a "problem" that ended up being cured simply with genuine Jeep repair parts.

Have you had the battery Load Tested ? Low battery voltage erases the stored idle setting and the engine will be hard to start and will not idle until the idle setting are re-learned.

The throttle body casting is not the problem, unless the holes for the butterfly valve pivot shaft have been significantly worn and are allowing extra air into the throttle body or the shaft is binding and not letting the butterfly valve close fully and/or function smoothly. Changing the fuel grade will not change anything except your fuel costs.

.

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post #3 of 13 Old 07-20-2019, 10:20 PM
TheBoogieman
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Mine acted the same way when my battery was going bad. X 2 on not using crap Chinese parts.

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post #4 of 13 Old 07-21-2019, 08:52 AM
billb2011
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I may be wrong but when replacing the TPS doesnt it sometimes need to be "tuned" or adjusted?

"If you lend somebody $20 and you never see that person again, you might consider that money well spent." ~unknown
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post #5 of 13 Old 07-21-2019, 09:35 AM Thread Starter
cHaB797n
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Now i disconnected the Idle control valve it wants to start.. This is the same old story. Like i said before. Maybe I will remove the throttle body then disassemble the idle control valve housing and see what's inside.

I used I used in NGK/NTK and Standard parts.
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post #6 of 13 Old 07-21-2019, 09:42 AM Thread Starter
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Now i disconnected the Idle control valve and it wants to start.. This is the same old story. Like i said before. Maybe I will remove the throttle body then disassemble the idle control valve housing and see what's inside. Still trying to get the fuel trims on my torque app.
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post #7 of 13 Old 07-21-2019, 10:13 AM
CJ7-Tim
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Battery test results ?

Numerous threads detail long and frustrating searches for a "problem" that ended up being cured simply with genuine Jeep repair parts.


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Originally Posted by billb2011 View Post
..... when replacing the TPS doesnt it sometimes need to be "tuned" or adjusted?

Renix engine controls need TPS adjusting, but after about 1990 they are all OBD engine controls.

.

A recent Gallup public opinion poll shows the NRA, at 58% approval, has a higher approval rating than either Hillary Clinton or Barack Obama.

Progressive Liberalism: Bringing you new Healthcare ideas so wonderful, they have to include mandatory participation ...

Originally Posted by Ronald W. Reagan: Government is not the solution to our problems; Government is the problem.
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post #8 of 13 Old 07-22-2019, 10:08 AM Thread Starter
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Battery Results are 12.56 not running and 13.37 at idle.

Today she is running good. Waiting for the problem to start again.



Thanks
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post #9 of 13 Old 07-22-2019, 08:14 PM
cpttuna
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new PCM?
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post #10 of 13 Old 07-23-2019, 04:54 AM
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new PCM?
Based on what diagnostic data ? The OP should start with the basics, which coincidentally are cheap and easy; some basic testing, some cleanup or grounds and wire connections, and some visual inspection.

.

A recent Gallup public opinion poll shows the NRA, at 58% approval, has a higher approval rating than either Hillary Clinton or Barack Obama.

Progressive Liberalism: Bringing you new Healthcare ideas so wonderful, they have to include mandatory participation ...

Originally Posted by Ronald W. Reagan: Government is not the solution to our problems; Government is the problem.
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post #11 of 13 Old 07-23-2019, 09:05 AM
jtec
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did you try to check for codes ?
do you have a vacuum gauge?
Any other issues - cruise control inop, airbag light on?

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #12 of 13 Old 07-23-2019, 09:22 AM
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Quote:
Originally Posted by cHaB797n View Post
Now i disconnected the Idle control valve it wants to start.. This is the same old story. Like i said before. Maybe I will remove the throttle body then disassemble the idle control valve housing and see what's inside.

I used I used in NGK/NTK and Standard parts.
NGK/NTK are usually good parts. There is Standard and I think US Standard parts. If its a light Blue box, then the parts might be OK. Still, I don't see them for sale any more. For TBS and CPS, I would use MOPAR parts. I think I can get MOPAR parts for the same price as parts from the Box stores. I did install a cheapie part some years back. The old part ran better.
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post #13 of 13 Old 07-24-2019, 08:45 AM Thread Starter
cHaB797n
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Since is plunged back in my temp and throttle control sensor XJ has been running well. Waiting
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