Intermittent "restricted performance" fault
#21
#22
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Hi dhog4n
I also have a Memoscan OBD reader, although mine is a U581. First time I used it I had the same problem - wouldn't link. Tried another car, and that wouldn't link either. Took a look at the connector at the car end of the cable they provide, and found that one of the pins had got bent, and would not have made the connection. Bent it -slowly and carefully - back into place with needle nose pliers and carefully plugged it into my XK8, and all was well. Linked first time.
This has happened a few times since.... the metal they use for the connector pins is very soft and you have to be very sure to plug the connector in "square".
Second issue...I cannot drive my XK8 with the scanner connected. It does all sorts of oddball things, including locking the transmission shifter. However it does work fine when working in the workshop.
Hope this helps!
I also have a Memoscan OBD reader, although mine is a U581. First time I used it I had the same problem - wouldn't link. Tried another car, and that wouldn't link either. Took a look at the connector at the car end of the cable they provide, and found that one of the pins had got bent, and would not have made the connection. Bent it -slowly and carefully - back into place with needle nose pliers and carefully plugged it into my XK8, and all was well. Linked first time.
This has happened a few times since.... the metal they use for the connector pins is very soft and you have to be very sure to plug the connector in "square".
Second issue...I cannot drive my XK8 with the scanner connected. It does all sorts of oddball things, including locking the transmission shifter. However it does work fine when working in the workshop.
Hope this helps!
#23
#24
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We had a day of heavy rain here about 10 days ago and the "restricted performance" fault reappeared. Rather than to-ing and fro-ing to the garage again, I decided to get out the tools and see what I could figure out for myself.
The first thing I noticed when I lifted the bonnet was water on each spark plug coil cover. As these are directly below the bonnet vents, it's easy to see how it got in. When I took the covers off, I found condensation on the underside of the covers, drips along the bottom edge of the coil recess and water in three of the spark plug holes.
I cleared the water out, greased all the electrical connections and applied grease to the steel surfaces of the coils to arrest the surface rust. I also found that one of the covers had been fitted the wrong way around and also previously damaged during removal. I put it back the right way round and used some sealant to keep out the water until a replacement arrives.
The long and the short of it is that, for the grand sum of zero money (and about two hours of my time) we now have a fully functioning XKR.![Smile](https://www.jaguarforums.com/forum/images/smilies/smile.gif)
Moral of the story: even with our computer controlled, multi sensored, gizmo ridden, fabulous machines some faults are traditional in their cause, diagnosis and resolution. Don't just trust the computer to tell you what's up - take a look yourself.
The first thing I noticed when I lifted the bonnet was water on each spark plug coil cover. As these are directly below the bonnet vents, it's easy to see how it got in. When I took the covers off, I found condensation on the underside of the covers, drips along the bottom edge of the coil recess and water in three of the spark plug holes.
I cleared the water out, greased all the electrical connections and applied grease to the steel surfaces of the coils to arrest the surface rust. I also found that one of the covers had been fitted the wrong way around and also previously damaged during removal. I put it back the right way round and used some sealant to keep out the water until a replacement arrives.
The long and the short of it is that, for the grand sum of zero money (and about two hours of my time) we now have a fully functioning XKR.
![Smile](https://www.jaguarforums.com/forum/images/smilies/smile.gif)
Moral of the story: even with our computer controlled, multi sensored, gizmo ridden, fabulous machines some faults are traditional in their cause, diagnosis and resolution. Don't just trust the computer to tell you what's up - take a look yourself.
#25
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Driver's side cover off showing condensation:
![Name: SANY0199.jpg
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Water in plug hole:
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Passenger side with water along the bottom edge. There was water in the two bulkhead end holes right up to the top of the spark plugs:
![Name: SANY0203.jpg
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Size: 88.2 KB](https://www.jaguarforums.com/forum/attachments/xk8-xkr-x100-17/156758d1501213953-intermittent-restricted-performance-fault-sany0203.jpg)
Close up showing water sitting under the coils:
![Name: SANY0205.jpg
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Size: 77.1 KB](https://www.jaguarforums.com/forum/attachments/xk8-xkr-x100-17/156759d1501213953-intermittent-restricted-performance-fault-sany0205.jpg)
Damaged cover positioned as it was removed (ie: backwards, leaving a big gap at the left hand end for water ingress):
![Name: SANY0199.jpg
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Size: 94.4 KB](https://www.jaguarforums.com/forum/attachments/xk8-xkr-x100-17/156756d1501213953-intermittent-restricted-performance-fault-sany0199.jpg)
Water in plug hole:
![Name: SANY0198.jpg
Views: 1662
Size: 83.6 KB](https://www.jaguarforums.com/forum/attachments/xk8-xkr-x100-17/156757d1501213953-intermittent-restricted-performance-fault-sany0198.jpg)
Passenger side with water along the bottom edge. There was water in the two bulkhead end holes right up to the top of the spark plugs:
![Name: SANY0203.jpg
Views: 1657
Size: 88.2 KB](https://www.jaguarforums.com/forum/attachments/xk8-xkr-x100-17/156758d1501213953-intermittent-restricted-performance-fault-sany0203.jpg)
Close up showing water sitting under the coils:
![Name: SANY0205.jpg
Views: 1604
Size: 77.1 KB](https://www.jaguarforums.com/forum/attachments/xk8-xkr-x100-17/156759d1501213953-intermittent-restricted-performance-fault-sany0205.jpg)
Damaged cover positioned as it was removed (ie: backwards, leaving a big gap at the left hand end for water ingress):
![Name: SANY0202.jpg
Views: 1589
Size: 95.2 KB](https://www.jaguarforums.com/forum/attachments/xk8-xkr-x100-17/156760d1501213953-intermittent-restricted-performance-fault-sany0202.jpg)
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cjd777 (10-11-2014)
#26
#27
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Mine had the same problem with the condensation causing random misfire on 3 cylinders. The 2 middle screws were missing on the cover and it bowed upwards so moisture could get in and the misfires and codes only occurred on rainy days. My coils are also rusty from the moisture and someone had broken the holes out of the coil connectors so the plugs wouldn't latch in and then they put dabs of silicon on them to keep the plugs from falling out. I also put dialectic grease inside the plug boots with a q-tip to keep moisture and/or oil from traveling up the plug. I replaced the missing screws. I haven't had a single misfire code since.
Dave
Dave
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