No I didn't pull the battery lead - is that significant?

 

After you do, it resets the stored parameters. It is usually called a "hard boot" and you might want tot try that now. If your engine is running better (different) than iot was before, no doubt some operating parameters are "wound up" to bad values.

 

I was planning to check the connections and was considering a hard reset which I'll do as well. But as ever it's raining so it will need to wait a while...

 

Did the reset and it's just the same. Starts at about 1,000 rpm, blip the throttle and it's 1700.

Didn't do this before. I assume what I need to do now is return to the original sensor and see if it does it otherwise it has to be something else that's coincidentally gone wrong. I did wonder if perhaps the electrical connections might be at fault but they seem fine.

Sigh.

 

Occam's razor says to check the throttleplate to make sure it is actually getting to full closed.

 

That occurred to me as well although I am tempted to put the old unit back first.

 

Another long and tedious post

I took the MAF off to look at the throttle body and butterfly valve. I put some carb
cleaner in and wiped round with a clean rag. I got some light black off
it as you'd expect but no sludge or gritty bits. I went round the
butterfly edges and reassembled being careful not have leaks.

I checked the various connectors including the sensor connector which I
also cleaned.

Started fine on the button.

Idle about 900+ which from cold I guess is OK.

Took it for a short run and clearly the idle is 'sticky' as you can tell
the engine braking such as it is on an auto was less firm and the instant
fuel economy suggested the engine was still working. Stopping the idle
was initially 1200 then sort of stepped down to 700 or so after a couple
of seconds. Usually I get 99 mpg when coasting but I was getting 78, 88
and so on. As fuel was getting low I thought I'd risk over the steep hill
to the village fuel station and it was fine. The instant economy is
always appalling up hills and nothing has changed.

Put 5 gallons in, went road the block faithfully doing 30 mph and then
hurried up the steep hill towards home. All was well although maybe the
idle was still sticky but hard to tell so then I reproduced my previous
test run which triggered the original problem by going out about 1 mile
then coming back in second so I could get some revs up. Ran fine up to
5,000+ rpm and I ran out of road. Kickdown was OK but didn't just red
line it like it usually did but I really was running out of road.

No misfire, no lumpiness just the usual Jaguar smoothness.

Back on the drive pulled up and idle dropped to roughly 700 very
quickly, blip the throttle and it dropped straight to 700 which it hadn't
before so maybe it's learnt to be a good big cat again and has its idle
set?

Encouraging but not definitive I think.

I may now fit the O2 sensor as one pipe was showing vapour while the
other one was not. I couldn't send the crank sensor back but the O2
sensor was unopened so they'll take it back but if after another longer
run it remains OK I think I'll change the O2 sensor as well.

So, I hope that is progress.

 

Did a 3 mile round trip with no dramas. Managed hills, roads and open road with foot to the floor to get the usual alarming 6,000 rpm and all seems well.

Sensible idle and the average fuel creeps towards its usual 24 mpg.

I feel optimistic.

 

I have 1995 X300 with nearly the same symptoms as Dr Mike. Very poor idle and would redline when cold, but would not run over 4000 RPM when warm. Cranking RPM were actually NEGATIVE. I took it to the dealer who ran scope and OBDII. advised: 1. replace spark plugs; 2. clean fuel injectors; 3. replace coil number 1; 4, bad catalytic converter on bank A with bad oxygen sensors. 4. also code for secondary air pump, but I have been down that road before without finding anything. I opted for catalytic converted because the car had exhaust leak and sounded VERY loud, and the oxygen sensors (two). But no more. I replaced the #1 coil and plug, and idle improved. But car would still not pull over 4000 RPM when warm; car still loud so I took to my local garage who told me that the exhaust pipe was cracked as it exited the new catalytic converter pipe, and it looked as if the dealer had tried using some mung to seal it. I took the car to my local muffler shop and they cut out the broken pipe and welded in a new segment. I was still unhappy as the car was not running right. then I saw this thread, and ordered a new CKPS and an Andy bracket. The CKPS came in a few days but it took longer for the bracket to arrive from across the pond. Then to wait for a warm day! Yesterday I replaced both the bracket and CKPS and took the Jaguar out for a sprint, a road test. Magic! Car performed as if it had a new engine! I test the resistance of the old CKPS and it read 1350 mOhms, so right at spec. But obvioiusly failing, I guess not generating the proper AC current to inform the ECU of engine speed.

So this was a VERY productive post. Here is the real kicker. I am also a doctor Mike! So this is karma redux!

Michael Levine
1995 X300 with 87,470
2015 BMW 328i X Drive

 

Congratulations on your repair! I know that changing the CKPS isn't always the "fix", yet I do know these cars are at a age, mileage?, where the crank sensor (as well as the ABS sensors) have lost some of their ability to produce a stable signal. I still suggest that any owners of these cars, along with any of the Marelli ignition cars consider changing these "sensors" with NEW ones. Its not a matter of if, but when they will fail.