2001 rough idle, tired everything I could find

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Mar 5, 2022 | 09:39 AM

#16

Idratherbewheeling

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Joined: Dec 2021

Posts: 25

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From: Oklahoma

Year: 2001

Model: Cherokee (XJ)

Engine: 4.0

Well I sprayed propane all round the intake and it made no difference. Pulling the injectors just causes a dead miss and I couldn't really tell any difference from pulling one to the next. I don't think the engine is missing that much, just something is making it shake a lot. When ever my foot is off the throttle, it shakes. Cold, hot, coasting down the road, if I'm not pressing the throttle, its not running right.

Mar 5, 2022 | 09:44 AM

#17

Dave51

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Joined: Jan 2017

Posts: 3,413

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From: Connecticut

Year: 2000

Model: Cherokee (XJ)

Engine: 4.0

Quote:

Originally Posted by Idratherbewheeling

You cant tell what the base timing is without the crysler scan tool because the computer controls all of that but moving the cam sensor definitely changes the timing. I had it come loose on the highway and it rotated about 20 degrees and killed the engine.

I would agree that they probably should be synced but as far as I can tell, the only people around here that can do that is the dealer. I'd rather not pay them to do that and not have it fix this issue.

You can sync it yourself with an entry level oscilloscope. I use a Hantek::

Mar 5, 2022 | 09:50 AM

#18

Dave51

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Joined: Jan 2017

Posts: 3,413

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From: Connecticut

Year: 2000

Model: Cherokee (XJ)

Engine: 4.0

Quote:

Originally Posted by Idratherbewheeling

...moving the cam sensor definitely changes the timing.

Well again, I do not KNOW what exactly what happens when it gets out of sync but perhaps so.

CPS/CKS out of sync:

Mar 5, 2022 | 10:01 AM

#19

Dave51

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Joined: Jan 2017

Posts: 3,413

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From: Connecticut

Year: 2000

Model: Cherokee (XJ)

Engine: 4.0

Quote:

Originally Posted by Idratherbewheeling

I don't think the engine is missing that much, just something is making it shake a lot. When ever my foot is off the throttle, it shakes. Cold, hot, coasting down the road, if I'm not pressing the throttle, its not running right.

Maybe it's not the engine per se.

Time to think out of the box...

MIL light burned out?

Mar 5, 2022 | 10:02 AM

#20

Dave51

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Joined: Jan 2017

Posts: 3,413

Likes: 399

From: Connecticut

Year: 2000

Model: Cherokee (XJ)

Engine: 4.0

Oh also that ^^^ was 2 separate thoughts...

Mar 5, 2022 | 10:10 AM

#21

Idratherbewheeling

Thread Starter

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Joined: Dec 2021

Posts: 25

Likes: 5

From: Oklahoma

Year: 2001

Model: Cherokee (XJ)

Engine: 4.0

The check engine light works. It turns on for a second when I cycle the ignition.

Mar 5, 2022 | 10:15 AM

#22

Dave51

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Joined: Jan 2017

Posts: 3,413

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From: Connecticut

Year: 2000

Model: Cherokee (XJ)

Engine: 4.0

2000+ uses all 4 oxygen sensors to determine fuel mixture so maybe wait till you get ELM327, read the O2 sensor voltages and see what shakes (LOL!) out.

Mar 5, 2022 | 10:23 AM

#23

Dave51

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Joined: Jan 2017

Posts: 3,413

Likes: 399

From: Connecticut

Year: 2000

Model: Cherokee (XJ)

Engine: 4.0

But it sure sounds like vacuum to me (too). Did you check everywhere? Brake booster? Some of those tubings that disappear into oblivion?

Mar 5, 2022 | 10:33 AM

#24

Dave51

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Joined: Jan 2017

Posts: 3,413

Likes: 399

From: Connecticut

Year: 2000

Model: Cherokee (XJ)

Engine: 4.0

And rather than guessing I would measure it.

Mar 19, 2022 | 10:54 AM

#25

bscunningham

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Joined: Mar 2022

Posts: 1

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Model: Cherokee (XJ)

I have a rough idle too when warm and it gets worse when in gear. What are you thinking that means.

Quote:

Originally Posted by agreen

Don't mess with the timing advance. Leave it at the factory spot.

Aside from the injectors and spark plugs, what all is new?
O2, plug boots, motor mounts? (the sorts of things you should have put in new when you swapped the engine)
Does it get worse when you put it in drive and are stopped?
Did you clean up the ground points?
Are there any codes?
Do you have access to a code scanner that reads live data?

Mar 19, 2022 | 11:26 AM

#26

lawsoncl

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Joined: Dec 2017

Posts: 4,365

Likes: 1,215

Year: 1989

Model: Comanche (MJ)

Engine: 4.0

Quote:

Originally Posted by Dave51

2000+ uses all 4 oxygen sensors to determine fuel mixture so maybe wait till you get ELM327, read the O2 sensor voltages and see what shakes (LOL!) out.

Beware that the cheap chinese mass-produced ELM327 Bluetooth readers do not work properly for newer vehicles. They're the squarish, often clear blue plastic housing ones for under $5. I have one of them I bought for $3 off eBay, which reads my older Tacoma fine, but totally freaks out the 2014 Cherokee trying to connect, causing all kinds of errors to popup on the screen because it doesn't do canbus correctly. The "car scanner" software on my phone even calls it out as one of the "bad" fake modules.

I looked at some review sites and bought a Tonwon brand (same as V-Link) BLE 4.0 Bluetooth reader last week and it works perfectly with all my vehicles with "car scanner" and "torque light".