89 yj 2.5 5 speed - JeepForum.com
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post #1 of 25 Old 08-17-2021, 09:40 AM Thread Starter
SPCKENDRICK
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89 yj 2.5 5 speed

Alrighty so my yj likes to run around 1200-1500 RPM I checked as many vacuum lines I could fine and tested the idle speed motor. I got it down to like 1000 but it wont drop below that and dumb *** California says it needs to be between 800-950 for them to smog test it.
Any Ideas

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post #2 of 25 Old 08-17-2021, 02:13 PM
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Okay... this may come off wrong, but... have you tried to adjust your idle speed motor?



I replaced mine but didn't have the means to adjust it/set it up the "correct way", so I didn't. I also didn't have the correct adjustment screw for it, I just found a screw that fit. I also never put a lock nut of any type on it. So every now and then I have to adjust my idle. I just turn the screw one way or the other to bring it up or down.



So I guess my suggestion is, turn the screw in a little and slow it down.

Silicone, the thinking man's duct tape.
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post #3 of 25 Old 08-17-2021, 07:46 PM Thread Starter
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Yes I did, now I will say I dont know the proper procedure for setting the idle speed motor. I briefly read something about a plug that extends the rod, but for the most part Im not sure. Im also not sure if the TPS sensor could have that much of a major roll on the idle I mean its just a bar that moves when the throttle blade opens I could also be wrong lol
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post #4 of 25 Old 08-17-2021, 08:28 PM
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Years ago I had a car with a bad TPS. It had a bad spot where it would think I let off the gas. Push past that and it would rev the engine to catch up to that pedal position.

That same TPS was dirty and caused some other issues. Cleaning it helped a bit, but ultimately replacing it fixed the problems.

As the bar moves, it changes the info being sent to the ECU. The other peeps here can explain exactly how it works.
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post #5 of 25 Old 08-18-2021, 05:26 AM
fishadventure
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Intake/exhaust manifold gasket leaking? Air leak tells the fi to add gas, gas and air =higher idle.
Does it idle high cold, too, or just up to temp?

The tbi jeeps are difficult with manifold/exhaust leaks. The unlit propane torch test is in order here.

[size=3]Shackles & D-rings are different things.
Cranking IS turning over
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post #6 of 25 Old 08-18-2021, 09:16 AM Thread Starter
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Im probably gonna buy a new tps just to eliminate it and its cheap anyways, as for the in lit propane test Im pretty sure I have an idea of what your talking about but please shed a little extra light on the process.
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post #7 of 25 Old 08-18-2021, 10:04 AM
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You can check for vacuum leaks by spraying something flammable, (like propane, or even better, carb cleaner), around all the hoses and manifolds of a running engine, and listen for an RPM change. The RPM change would indicate a vacuum leak.
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post #8 of 25 Old 08-19-2021, 05:17 AM
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Unlit thin torch head moved around the manifold gasket, tbi base, hoses, even exhaust joints, front axle disconnect harness etc. you can poke it in all the cramped places and it will have an effect in rpm if there’s an air leak.

[size=3]Shackles & D-rings are different things.
Cranking IS turning over
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post #9 of 25 Old 08-19-2021, 05:21 PM
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Quote:
Originally Posted by fishadventure View Post
Unlit thin torch head moved around the manifold gasket, tbi base, hoses, even exhaust joints, front axle disconnect harness etc. you can poke it in all the cramped places and it will have an effect in rpm if there’s an air leak.
just to clarify...

Fish doesn't mean with the torch head ignited. Just releasing the gases within the tank it's attached to. Maybe this wasn't necessary, but ya just never know in the /f12


Man, California

~YJOTM MAY '16, JULY '19~


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post #10 of 25 Old 08-19-2021, 06:57 PM
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I'd be worried about finding exhaust manifold leaks instead.

Silicone, the thinking man's duct tape.
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post #11 of 25 Old 08-19-2021, 07:21 PM
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Propane’s sorta safe because it doesn’t / can’t ignite less than or over than ~5% propane:air concentration

[size=3]Shackles & D-rings are different things.
Cranking IS turning over
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post #12 of 25 Old 08-27-2021, 09:40 PM Thread Starter
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Ok so I did the propane torch test and yes I was aware he meant unlit lol. Didn’t really find anything but I replaced the intake/exhaust manifold gasket and I replaced the EGR. I also cleaned the throttle body out extremely well and pulled the idle speed motor apart to make sure nothing was broken. And I still have the same issue except now it idles at like 1000. Smog guy says it needs to be below that!
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post #13 of 25 Old 08-28-2021, 02:52 PM
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Mighta been Luuca and maybe jeeperdon? have posted destructions in the past on adjusting the idle stepper

Anybody got a link?

[size=3]Shackles & D-rings are different things.
Cranking IS turning over
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post #14 of 25 Old 08-30-2021, 10:17 PM
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Cool tip on the propane. I have a torch on my truck and will use this method to check for exhaust gasket leaks. My '90 2.5L YJ also idles at 1000. I guess my question is are the emission guys giving you the rpm reading or is it your gauge? YJ gauges are known for inaccuracy. Just a thought. 100-150rpm isnt much of a difference.



Good luck!
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post #15 of 25 Old 08-31-2021, 05:18 AM
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Quote:
Originally Posted by SevenSlotAddict View Post
Cool tip on the propane. I have a torch on my truck and will use this method to check for exhaust gasket leaks. My '90 2.5L YJ also idles at 1000. I guess my question is are the emission guys giving you the rpm reading or is it your gauge? YJ gauges are known for inaccuracy. Just a thought. 100-150rpm isnt much of a difference.



Good luck!
Propane works in the intake and vacuum side because it makes it to combustion. Its not really gonna do anything on the exhaust side except blow it out the exhaust
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