I just traded a old Jeep Cherokee i had into a 1991/92 XJ40. The XJ40 is not in good shape. I have a question: I think its only running of some of the cylinders because it goes really bad, no power at all! When throttle, black smoke come from the exhaust, a lot of black smoke! Sounds like engine is misfiring. How do i begin troubleshooting this? Take out all the spark plugs and see if all plugs is sparking when I try to start the car? And what to do next? Is this a known problem with these cars? And could it be something with the injection? Cheers

 

I would start with checking the spark plugs and make sure they are all the same color. They should be a medium to dark brown. The below is a color chart for reference. Next I would check to see if the cylinders are all getting a spark. You may have one or more wires bad or a cracked distributer cap. If the electronics pieces all check out OK then try cleaning out the throttle body and possibly the injector nozzles. For more advanced procedures I would refer to a Jaguar technician or British car specialist.

http://www.verrill.com/moto/sellingg...colorchart.htm

 

Thanks a lot!! I will try it in the weekend. Will come back with update

 

Now i have done a littlebit troubleshooting on my XJ40. The first thing i did was to replace all 6 sparkplugs. Then i tryed to start the engine. Now it runs on all cylinders and no misfiering.

But i still have the problem that the engine will not run if i dont throttle. If i disconnect the cable who goes into the "unit that measure airflow" (do not know what this part is in english(airflow meter)) and also disconnect the cable who goes to the sensor next to the airflow meter, the car runs perfectly without throtteling. But it still uses way to much fuel. Maybe the airflow meter is broken and it provides the engine with wrong ammount of air and fuel? If i throttle real much (4-6k rpm) it is still came out some black smoke from the exhaust, but not as much that came before.

 

Hi, I'm no expert, but check the threads about MAF (that's the part you are talking about).

Also check, throttle body cleaning threads, and O2 sensor threads.

Perhaps some of our more knowledgeable friends can offer advice.

 

axelaxel,

It looks like you are making progress. I would recommend going down the path Richard indicated as it seems to be either fuel system or emission system related. Cleaning up your MAF sensor and throttle body is fairly easy if you use a spray cleaner like CRC or its equivalant.

When you start up your car are any messages displayed? When I had a 90 XJ6 the message center would display a warning message if something was wrong. Also, if I remember correctly, the owners manual had a section on the various warning messages. Other XJ40 owners in this forum may be able to add more information for you.

Good luck,

Mike

 

Thanks Mike!

I will try to clean MAF sensor and throttle body with the CRC airflow cleaner. Where can i find the throttle body?

No error messages is displayed when I start up the car. Only the miles is displayed. When i disconnect the contact to MAF and O2 sensor the engine error lamp lights, but the engine runs good (just to high fuel consumption). When the contact is connected to the MAF and the O2 sensor the car does not run good (but same fuel consumption).

 

Hi axelaxel,

The throttle body is pictured in the center left of the engine. It's under the throttle linkage. You will have to remove the intake tube running from the air cleaner. It's been a while since I had my 90 XJ6 so I'm operating from a sketchy memory. Some current or recent owners could shed more light on it.

 

Pretty engine you have there Mike, puts me to shame.

As stated the TB is behind the bit with the bellows. When you remove the rubber bellows they and TB will need a clean.

Be careful not to puncture the bellows, and think about which way round you are replacing the jubilee clip for tightening access. You don't want to have to remove the bellows a second time just to turn the clip around.

This you will realize once you have replaced them for the first time.

For error messages, what happens when you press the VCM button? Car running.

 

Hi Richard,

It's not from my engine, I just got a picture from Autotrader.com for reference. At least my memory hasn't totally gone. I forgot what the silver thing is between the air cleaner and the throttle body hose is though. I think it's a Mass Air Flow Meter assembly though.

Mike