high rev on start up

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Dec 16, 2017 | 10:09 PM

ChrisOKF

Thread Starter

Newbie

Joined: Aug 2017

Posts: 2

Likes: 0

From: Frederick, MD

Year: 1999

Model: Cherokee

Engine: I-6

high rev on start up

99 XJ that I'm doing a restore on. Stripped the motor down and replaced all worn parts. When I went and fired it back up for the first time it rev'd straight to 5k. It ran and idled fine before I cleaned and replaced parts. Stock manifold, stock(same) TB. I checked all bolts and vacuum leaks and still it does the same thing.

Any help would be appreciated

Dec 17, 2017 | 08:30 AM

cruiser54

::CF Moderator::

Joined: Aug 2011

Posts: 43,971

Likes: 1,577

From: Prescott, Az

Year: 1990

Model: Cherokee (XJ)

Engine: 4.0

Your intake manifold is not seated properly.

Probably hung up on a locating pin. Feels tight but isn't seated.

Dec 17, 2017 | 08:43 AM

TrailerTrash

CF Veteran

Joined: Jun 2017

Posts: 2,215

Likes: 635

From: Hangover, PA

Year: 1998

Model: Cherokee(XJ)

Engine: 4.0L

Quote:

Originally Posted by cruiser54

Your intake manifold is not seated properly.

Probably hung up on a locating pin. Feels tight but isn't seated.

Bingo. It might be hard or even impossible to actually see how it is not mated properly because of how everything is placed on the engine.

Dec 18, 2017 | 03:34 PM

fb97xj1

CF Veteran

Joined: Dec 2015

Posts: 3,038

Likes: 338

From: PA

Year: 1997

Model: Cherokee

Engine: 4.0L

Intake manifold, like said. As soon as it idles high like that on startup, shut it off immediately. Especially if its a cold start. Ive seen engines throw stuff doing that.

Dec 18, 2017 | 03:56 PM

Bugout4x4

CF Veteran

Joined: May 2015

Posts: 4,481

Likes: 18

From: Arizona

Year: 97

Model: Cherokee

Engine: 4.0

I sure didn't like that rattle it made when you shut it off... That's how push rods get bent.

Sep 16, 2021 | 06:54 PM

Newxj99

Newbie

Joined: Sep 2021

Posts: 2

Likes: 0

Model: Cherokee (XJ)

Did it work?

I am having the same issue. Newbie… did you get it with checking the manifold?

Sep 20, 2021 | 04:17 PM

cruiser54

::CF Moderator::

Joined: Aug 2011

Posts: 43,971

Likes: 1,577

From: Prescott, Az

Year: 1990

Model: Cherokee (XJ)

Engine: 4.0

Have you had your intake manifold off recently?

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Sep 21, 2021 | 02:33 PM

Newxj99

Newbie

Joined: Sep 2021

Posts: 2

Likes: 0

Model: Cherokee (XJ)

Quote:

Originally Posted by cruiser54

Have you had your intake manifold off recently?

Yes I replaced the exhaust manifold but of course had to take the intake off. Is there a way to check to make sure it’s on the back pin correctly? Can’t really see back there.

Sep 23, 2021 | 07:36 PM

cruiser54

::CF Moderator::

Joined: Aug 2011

Posts: 43,971

Likes: 1,577

From: Prescott, Az

Year: 1990

Model: Cherokee (XJ)

Engine: 4.0

It's not seated. It will be necessary to loosen it all up and get the intake manifold over the pin.

Sep 23, 2021 | 09:04 PM

#10

psf4x4

Member

Joined: Jul 2021

Posts: 120

Likes: 29

From: Down east, NC

Year: 2000

Model: Cherokee (XJ)

Engine: 4.0

Pete and repeat

Quote:

Originally Posted by cruiser54

It's not seated. It will be necessary to loosen it all up and get the intake manifold over the pin.

Do you and everyone else get tired of answering the same question you did 4 years ago on, especially on a resurrected thread for which the answer was provided for the exact problem by you?

Im in the middle of changing my head gasket. I’ve read enough to know that I need to make sure my intake is seated correctly well before I fire it up for the first time.

Thanks.

Sep 23, 2021 | 09:30 PM

#11

cruiser54

::CF Moderator::

Joined: Aug 2011

Posts: 43,971

Likes: 1,577

From: Prescott, Az

Year: 1990

Model: Cherokee (XJ)

Engine: 4.0

I only responded to Post 6 when it came up. I don't have time to forensically disect each thread's history before offering help.

Oct 1, 2024 | 02:39 PM

#12

Don Roger

Newbie

Joined: Oct 2024

Posts: 1

Likes: 0

Prolem solved? I've the same problem after charge the cilinderhead gasket

Quote:

Originally Posted by ChrisOKF

99 XJ die ik aan het restaureren ben. Motor uit elkaar gehaald en alle versleten onderdelen vervangen. Toen ik hem voor het eerst weer startte, ging hij direct naar 5k. Hij liep prima en stationair voordat ik hem schoonmaakte en onderdelen verving. Standaard spruitstuk, standaard (zelfde) TB. Ik heb alle bouten en vacuümlekken gecontroleerd en hij doet nog steeds hetzelfde.
https://www.youtube.com/watch?v=BReduiVtiYg

Alle hulp is welkom

after changing the cilinder head gasket my jeep cherokee have the same issue as yours, all sensor are new.
the manifolds are good fastned on the engine.
I still hope you have find out what the problem was..
Tnxs!