2000 Cherokee Misfire Trouble

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Mar 3, 2016 | 06:10 PM

#16

Guntar13

Senior Member

Joined: Jan 2012

Posts: 635

Likes: 2

From: Indiana

Year: 1999

Model: Cherokee

Engine: 4.0

I'm gonna beat the dead horse here that you need accurate fuel pressure readings at the rail...

Mar 6, 2016 | 08:15 PM

#17

RBLUXJ00

Newbie

Joined: Feb 2016

Posts: 5

Likes: 0

From: So Mo

Year: 2000

Model: Cherokee

Engine: 4.0L 6Cil

Quote:

Originally Posted by Ryan Fairchild

So there's three lines coming from the tank going toward the front of the vehicle - the fuel line, the electrical to the pump, and a vacuum line. I'm assuming, unless there's another vacuum line on top of the tank, that is the vacuum line you are referring to. In that case, there is no fuel coming from that line before or after I turned the key on...the car hasn't been started in a few hours, would that make a difference? Or should I run the car for a few minutes, then shut it off and check?

I do not think it should make a difference but I would try if I were you, also I am sorry my reply came so late, I've been camping with no service the past few days. I'm not too sure what else I would do, but maybe try what Guntar13 suggests, I'm sorry I couldn't help here, good luck!

Mar 7, 2016 | 01:15 AM

#18

Radi

CF Veteran

Joined: Apr 2012

Posts: 5,302

Likes: 23

From: Wisconsin

Model: Cherokee

Quote:

Originally Posted by Ryan Fairchild

RBLUX's post is referring to the pre-'96 fuel pressure regulators that were mounted on the fuel rail. They had a vacuum line that modulated the fuel pressure. This advice does not apply after 1995 model year, 1996+ the regulator became part of the fuel pump assembly and is in the tank.

The line you are referring to on top of the tank is the vapor recovery line. There shouldn't be liquid fuel in it.

Checking fuel pressure would certainly be useful.

Mar 7, 2016 | 06:52 PM

#19

Ryan Fairchild

Thread Starter

Newbie

Joined: Feb 2016

Posts: 10

Likes: 0

Year: 2000

Model: Cherokee

Engine: 4.0

So finally the computer threw a code today, P0303, cylinder 3 misfire. I checked the injector and it was fine, working properly, so my next step was to try a coil, even though it ohmed out fine, and that seems to have been the issue. Threw in a new coil, and it runs nice and smooth. Thanks for all the troubleshooting help!

Mar 7, 2016 | 07:02 PM

#20

Guntar13

Senior Member

Joined: Jan 2012

Posts: 635

Likes: 2

From: Indiana

Year: 1999

Model: Cherokee

Engine: 4.0

Hopefully this stays fixed for you. Keep an eye on it there is a known issue with heat soak in the fuel rail boiling the fuel essentially. It throws codes for cylinder 3 misfire when it's happening. Just an FYI, look up injector heat soak and you'll learn all about it