Jagy4321,

Can you check your fuel trims? I'd like to know what your LTFT is pegged at.

Your mileage isn't too good. I had the same problem which was cured only after I replaced the TPS, which tested well, but apparently had something in it causing the ECU to overfuel the engine.

 

My X300 4.0 NA with bracket and 98Ron fuel, averaged over many years 28MPG (imperial). 50/50 city/highway.

When only highway and flat road and cruise control to 125km/h, 34MPG (imperial).

 

I have also experienced 35 imperial mpg.
But I was cruising at 70km/h in all flat terrain.
Reset the cars computer after having reached the cruising speed and after 80 kilometers it averaged 35 imperial mpg .
But as soon as I reached the highway I set the cruise control to 115 km/h and with some more hills etc I averaged 28 imperial mpg

 

It was actually from Golden to Kamloops, BC through the Canadian Rockies. I think a big factor is most of that is through the national parks where the speed limit is 90 km/h, and in the mountains outside the park it is also mostly 90 km/h. The diff would have hurt my economy, not helped, as I replaced a 3.58. The only reason was I wanted limited slip and I found a 3.77 limited slip as a NOS diff for cheaper than rebuilding the one I had.

 

I will check that thank you.

 

Hi Vee,
I checked my LTFT Trim this morning while on the way into work. I used the Torque ,the application for android. It came in at -1.56 I don't know how bad or good that value is.
What I will say is a few weeks ago I got stuck at work one day when I got bad gas. It wouldn't start at all. I put fresh gas in it along with Marvel Mystery oil and gas line antifreeze heavily mixed in. It start right up after that but I wonder if that whole episode screwed something up. Also previous owner said he had a exhaust manifold leak that he previously had repaired. I don't hear any exhaust leaks but maybe i do have one enough to screw things up.

 

 

That is good news Vee,
Thank you. I don't think I really have a heavy foot. But I will say that my terrain driving to and from work is rolling hills. I know the previous owner did some work with the ignition coils as a few extra ones came in the trunk. It is on my to do list to check what plugs are in there just so i know. Also I do think I should check my idle control solenoid, sometimes it idles high for a little every now and then.

 

There should be two values for long term fuel trim (LTFT); one for the front 3 cylinder and another for the rear. Having one value close to zero is good, but the other one should be similar. If part of the closed loop fuelling control system fails, then the corrections can reach +25% or -25% which is very bad and can lead to very poor fuel consumption.

 

Thank you XJRengineer, I will pull up the second value for LTFT and monitor it then.

 

So i quickly found the second LTFT trim yesterday and pulled it up along side the first one to monitor on the way home. When I was leaving work it was still at -1.56 for both of them. I checked when I got home before turning it off and said 0 for both. Did a double take there. But I confirmed it this morning. They both stayed at 0 the whole way to work.
Last night I needed to change a headlight bulb on the left side of the engine, I found it was easier to access the bulb by removing the air filter and it's cover. Upon doing so it looked like the crankcase ventilation that connects to the bottom of the air filter box pulled out of it, the one from the right side of the engine.. Not sure how long it has been that way, but it is fixed now. Wonder if that would effect fuel economy to some degree.

 

Hi Andy,

Out of curiosity what outside of exhaust system/air leaks can cause the closed loop system to fail?
On an unrelated point are your rear anti-roll bar items now available to buy?

Thanks,
nickdabs
Nick

 

The oxygen sensors are a likely failure point if original on a vehicle that has done over 100,000miles.

Yes, I'm now offering rear anti-roll bar upgrade kits.

 

Can you tell us more about the roll bar upgrade kits, please Improved drop links?

 

At the risk of getting "off topic" on this thread, I have created a separate post on this subject. I offer front and rear drop links assembled with spherical bearings, to remove all of the compliance associated with the metallastic bushes of the standard parts. The rear drop links are intended to be used with a much stiffer anti-roll bar taken from the XK8. Please read my other posts or send me a PM , if you want more details.

 

Hi Andy,

I installed the bracket from your latest new batch received in early July. My car couldn’t start after installation. I revert back to my old bracket and the car could start normally.

Anyone who got the recent new batch facing same problem?

Kindly advise...

 

The AJ16 engine starts with the Cam position sensor at first then reverts over to the crankshaft position sensor for the rest of your drive

If the connector of your Cam sensor is removed ( simulating it failing , CEL code P0340 ) the engine will still start but takes a few more revolutions

It takes a few more revaluation because for every turn on the cam there is 2 on the crank in a 4 cycle engine

There are 6 targets on the cam sensor so in the starting sequence the ECU can determain The TDC of each cylinder ( or the best it can with the targets accuracy )

With the Crankshaft only as the single target come around is it the TDC of the # 1 or the TDC of the X cylinder of the compression stroke

The ECU must try the first revolution as the # 1 TDC and if unsuccessful will electronically shift to the second time around as the # 1 TDC for the rest of your drive

With the Andy bracket the 5 degree shift in position may be too much for the ECU to cope with as it relearns this crankshaft sensor only starting sequence

Another thing is the bad environment of the crankshaft sensor location

You may have disturbed it enough now to where it is bad to the point of failing

Look for CEL of P0335 for crankshaft and P0340 for the cam

reference page 126 of this doc

http://www.jagrepair.com/images/Trai...20-%202000.pdf

 

Thank you so much for the long writeup and sharing the pdf, it adds up to my knowledge from googling for information, understanding how a Crank position sensor works and gave me the confidence to give it a shot again to install the bracket as I believe the first failure was maybe bad luck. And know what! Car fires up at first crank woohoo! Now fingercrossed, going to go for a test drive

 

Dear All,
It has be a long time since I posted on this thread because I have had problems finding a machine shop that can manufacture these brackets for me long term. I have now found a very good machinist who has made several batches which have enabled me to satisfy all the back orders that have built up. I now finally have a stock of parts (see photo), so I wanted to let everyone know that these brackets (replacement for EBC5017) are available again for 1993MY and onwards AJ6 engines and all AJ16 engines. We will soon be making a batch of brackets to replace the bracket (EBC1253) used on late 3.6 L and earlier 4.0L / 3.2L AJ6 engines.

 

Hi XJRengineer, do you know if the internal (not the external harness) wiring harness on the XRJ6 GM4L80E transmission is the same in all of these GM4L80E transmissions or is it also different in the Jaguar. I have a 1995 X300 XJR6. I also purchased one of your brackets back in 2012 and she returns 30+mpg at freeway speeds (110kph) from Gold Coast QLD to Sydney, the bracket is a brilliant modification, thank you.