Injection system

["tid.rum" <tid.rum@swipnet.se>]

Hi,
I am a swedish guy owning and driving a 1986 XJ-S V-12.
Up to now my cat has been fooling around with me a bit.
Intermittently it has been running very rich.
First problem I discovered was a bad throttle potentiometer which has 
now been modified while I am thinking of a final solution (an 
alternative to spending around USD 300 at the Jag dealer here in 
Sweden). Since the engine has continued to run rich from time to time 
I have continued my troubleshooting. Today I found out that something 
is wrong with the ECU coolant temperature sensor (on the left 
thermostat housing). I measured the voltage between 
ground and one of the connectors and when I started to check the 
meter the value decreased from around 2 volts (engine just started) 
just to stabilize at 1,0 volts when warmed up. Taking the car on a 
test drive I noticed that the voltage suddenly jumped up to app. 2,1 
volt and when accelerating the power was gone and only result was a 
black cloud behind. Just as unexpected the voltage dropped to around 
0,95-1,05 and the power was back.

Q1: Is it possible that the temp. sensor gets fooled by air trapped 
in the thermostat housing (i.e. if the thermostat has been mounted 
incorrectly, pin is not upwards)?
Q2: Or is this a common failure part?
Q3: Has anyone replaced the original Lucas part (DAC 4737)with an 
equivalent such as Bosch? Any part numbers?
(Again, the dealer wants to to rip USD90 of me).

Any advice will be appreciated.
Please reply directly to me. I am not on the list yet.

Alex

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