01 xj check engine light help

[Cottontail]

Ok since I do not own a scanner tool how can i delete the code?

If you are worried about it, take it to your local Advanced Auto, or Auto Zone, or otherwise and ask them to test and clear it with their scanner. They read code for free.

 

[01yellowxj]

Then pop the hood and follow all the vacuum lines from the exhaust manifold (on the 2001 there are 3 of them) and see if they are cracked or popped off the nipples.

Intake Manifold





When checking all the vacuum lines from the Intake manifold make sure to trace them over to the passenger side and all the way down to the front bumper. If you have cruise control be sure to check those lines as well.
My 2001 had that issue and it was the vacuum line to the vacuum chamber behind the bumper on the passenger side.
I'm glad my 2000 don't have that extra emission / vacuum thing over in the passenger side fire wall area.

I know auto zone here will not delete codes anymore. Ask around and im sure you will know someone with a scanner.

 

[covey88]

ok i check and replaced all vacuum line that looked even remotely bad. Code came back (i was able to talk a advance auto guy to clear it for me). But i have noticed a pattern to the code coming on and maybe this will help. each time the code popes it is when i have to drive with on and off again throttle, either in stop in go traffic, traffic that cant maintain a speed, if i am able to not do the whole on the throttle then off the throttle and just maintain a steady peddle or slower accelerating speed, then i don't get the code (13hr drive with steady speeds and gentle throttle no code, 10min drive in Wilmington traffic popped code)

 

[covey88]

Oh and everything on jeep works the way it is suppose to, cruise, a/c, gauges,ect.. just so you know that also.

 

[covey88]

any new ideas?

 

[sbxj]

I see you changed your vacuum lines.
sorry, nothing to add mate

 

[Ecomike]

How is the brake booster, any sign of vacuum leak there? I found mine turning the car off, and listening under the hood to locate the leak, It was a tiny crack in one of the thin tubes. I found another the same way that was a brand new vacuum hose that was oval on the inside wall, not round.

 

[covey88]

hum, it is just driving me crazy that slow throttle and highway driving at steady speeds is fine but city driving in down town traffic sets it off

 

[McQue]

I would refocus on the advice in post #5 and #8 of this thread. If you can't find the problem this way you will have probably have to bring it to a shop and have the lines smoke tested to find the leak.

 

[Ecomike]

hum, it is just driving me crazy that slow throttle and highway driving at steady speeds is fine but city driving in down town traffic sets it off

It is caused by the huge drop in engine vacuum during deep acceleration (heavy foot), combined with a small vacuum leak in just the right place.

 

[covey88]

Have done everything in both post minus charcoal canister, what xo i check just the lines? Cause i have done that. And will a smoke detections fined this leak? Thought I read online that it would not. If so I will call around to see how much it cost.

So if I can ships a heavy foot it should not pop the code? And this seems to just be a vacuum leak, not a part malfunction right?

Thanks guys i really appreciate it!

 

[Ecomike]

I would not rule out a part malfunction completely.

 

[Ecomike]

I have an idea. You could use a vacuum gauge and move it around to various vacuum lines, then goose the throttle to localize the source of the leak? The one area that reads the lowest vacuum might be the general area of the leak. I am no expert on the 01, but I do know vacuum, and I would think the sensor could be suspect as well? But yours sounds like a small leak close to the sensor and the area the sensor is designed to watch. Is there a one way check valve in the vacuum lines that could be bad or missing????

 

[covey88]

Ok, then what could be malfunctioning, and how do I test/check? Purge valve?

 

[covey88]

Does each line have the same vacuum numbers going to them? Or just give it throttle and see if it drops off?

 

[Ecomike]

The larger lines closest to the intake manifold will drop the lowest and recover faster time wise since they are closer to the source. Smaller lines will not drop as fast or far unless there is leak nearby. I think there are at least 2 check valves in yours, maybe more. The brake booster has one, and the feed to the AC controls at the firewall has one (if your year still used vacuum controls in the HVAC under the dash)????

I have never worked on the new jeeps so that is about all I can offer.

One other diagnostic tool with a vacuum gauge could be to clamp off one line at time to see if the system vacuum increases. If it does, then the closed line has the leak!!!

 

[Ecomike]

I would refocus on the advice in post #5 and #8 of this thread. If you can't find the problem this way you will have probably have to bring it to a shop and have the lines smoke tested to find the leak.

That sounds like good advice. Did we rule out the gas cap?