1999 xj8
After unblocking the part load breather orifice which I believe was causing oil in air filter and replacing a cracked part load breather tube with a new one, I started the car and it changed back and forth between normal smooth operation and Restricted performance messages (rough almost like one misfire) . I applied accelerator at times and it went away but a few minutes later it comes back.

I read somewhere that resetting the ECU by touching the battery terminals for 5 seconds will recalibrate it.. Could this be a requirement for this situation as car wasn't breathing right until now. Can this explain the rough running I am experiencing as the ECU is shutting engine down to an extent somehow to protect itself.... With the air NOT exiting the main breather tube (as part load breather is now open/unblocked) and part load breather to throttle now NOT sucking in air to throttle base (it was cracked) the air flow has all changed.....back to as it should be...... does the ECU need to be recalibrated for this all hence a hard rest?

best
Peter

 

I did a "hard reset" of the ecu by connecting battery terminals for a minute... no change.
I will clean electrical connectors around throttle that I had disconnected while doing the above repair and clean with electrical contact cleaner.
advise appreciated
Peter

 

Sounds like an intermittent dodgy connection/wire broken? problem to me from the way it comes and goes, I think you are on the right track...just my thoughts on it....Allan

 

Inhibited Performance... is the mark of very very poor engineering. My first suggestion is get rid of your jaguar. Some folks in here have spent upwards of $5,000 at the dealer and painful hours of searching to find out what is the root cause and NEVER finding it. I have the same problem and have reset about half the electronics (very very poor design). Now I get this message and others about ABS brakes and suspension system, but they go away and come back intermittently. I'm trying to GET RID of this slump of engineering but the lights keep coming on. Lots of times when I turn off the car and the start it again (at a stop light sometimes), all the warning lights (check engine, abs) and messages go away - what a work of engineering! Sorry to say even though I love to work on my own cars, I will NEVER buy another Jaguar. They are beautiful on the outside, poor interior quality, mechanically smooth, and a nightmare of electronics. I wouldn't give it away to my worst enemy!

 

@ Nzane
Before you get rid of it, check your battery. Everything you have stated points to a failing battery.

Put it on charge and leave it overnight, then reconnect and try again. You might just be surprised.

These cars are renowned for being battery hungry and they must be maintained in tip top shape in order for the car to operate to its full potential.

 

Hang in there Peter, you've obviously put a great deal into this car, I can't advise but
the guys above and others will help!
I actually think the abbreviated post heading may have confused people but you will get help, the guys and gals here are cool and you'll get sorted, hopefully at not too much expense or ordeal!
Plus, I admire your hands on approach!
Take care, Stu

 

Hi Peter,
Lets get medieval on its ***.
Disconnect the battery and put on charge and leave it.
Go around the whole car and check/clean the ground points.
Check the fuel filter.
Check the adjustment on the throttle cable.
The work you have already carried out, check it again.
Check the air filter.
Disconnect/clean and check all sensors on the engine, throttle body and MAF.
Check all relays and fuses are seated correctly.

Take your time, do it methodically, make a list if needs be.

Reconnect the battery, reset any memory functions, insert the radio code and then with fingers crossed, try it again.

You've done a lot of good work already but as with anything, preventative rather than reactive maintenance is always the best policy. Even more so as the car gets older.

Keep us updated and don't let it beat you, we will win in the end.

 

nzane:
I suppose I understandyour frustration, BUT, blaming "RP" is counterprodutive to understanding the solution. RP is a result of some problem in the engine control system. It is designed to prevent the engine from damaging itself! It IS NOT, in and of itself, the problem. It is the car's solution to the problem. If your car has a problem, it must be resolved, then the RP will go away.
Now, finding then fixing the various problems that result in RP obviously is not easy, or people would not have to spend time and money fixing them. The car's diagnostics are not very good for recording the RP trigger, so other methods must be employed. Many folks come on here saying " I have RP, what do I do? And, there is no one answer!

 

There are usually DTC codes when RP is set. A code reader will be necessary to determine what they are, and some diagnosis will help pin point the cause of the codes being set. If there are no codes, pending or current, then the problem is likely due to a dirty or defective throttle body. If it's not the throttle body, then it's likely the battery. I just replaced my battery (got a good deal, BTW, $112 at AutoZone). I think the heat got to it. It's been very hot here lately, and I was getting some spurious messages on the message console, but the car would start fine. Due to the placebo effect (maybe) the car seems to be running better than ever, and no messages.

 

As always, you need the codes that the ecu sees in Rp. Without this info, use equate any further diagnosis equal to driving with your eyes closed

 

Yes... please get rid of your Jaguar since you obviously lack the skills to find issues and solve them and do not respect the heritage of the car itself.

Most problems start with the MAF and intake and then go down the line to find out what the RP issue is.. just cause you THINK there is no airleak, doesnt mean its not there, i struggled for 2 years on it. Actually quite simple to just make your own and seal it yourself. I have 160k on mine and the engine and trans work great, i just had to deal with rubber failing from the Florida heat, suspension from 160k miles and other things ANY car would fail at in this time and mileage.

The car is strong, the character of the x308 is almost unmatched, its a beautiful car. A little care, and some upgrades and you'd be pressed to find even a modern competitor for the class, style, performance and comfort.

I have 2 mercedes and i STILL prefer the Jaguar and still won't buy another car.

 

Gentlemen
yes I found the problem
I connected an ELM327 Bluetooth OBD2 scanner that I bought for $12 and connected it up to EASYOBD2 software which is free on my PC.
The trouble codes it gave was ignition coil 6 malfunction.. so I swapped coil 5 and 6 and then tested it again.. the error that came up was ignition coil 5 malfunction. This implies the coil a orginally at "6" was bad and not the wiring/connectors to it. So I have ordered a new coil.
The only other error that came up was a "stored" historical error of the knock sensor having high voltage.
The only explanation I have for this all this is that maybe the wiring got wet somewhere when I was cleaning the engine bay under the "jaguar" covers. I was very careful NOT to splash and mineral turps around but MAYBE a pindrop of the liquid shorted something wrt the coil/knock sensor. I just dabbed the paper wipe in the mineral turps bottle and wiped oil/grease etc off the cam covers. I am very surprised at how sensitive the electricals are if this is the cause of the problems.

Anyway I tested the car a few times since and the knock sensor high voltage error never came back. The coil problem was the same.

My advice is : buy and ELM327 Bluetooth scanner for $12 and download that free OBD2 software... otherwise these cars are impossible to handle electronically. The local mechanic I have heard wants $100 just to scan a car.... it pays for itself.

best regards
Peter

 

Happy for you mate, get it fixed and take her for a spin. Will make you feel a lot better.

 

The failed knock sensor on my XJ8 (new type, with hole, not stud), and pictures of the new type I have seen here, all show numerous cracks in the plastic housing. I surmise that the plastic cracks allow moisture to infiltrate the sensor element.

BTW, in my case, the bad sensor measured 35K ohms, while good sensors measure 200k or so. The bad sensor was occaisonally throwing codes, but did show a pretty good output on the scope when "tapped".

 

2 YEARS! LOL.. 2 years looking for a mechanical problem. I've tuned Jaguar V12's, XKE's, XJ6's, MG's, Austins, Opel GT's, Triumph TR6's, Porches. Never took me more than a couple of days if I can even remember that long to find a problem, but two years, LOL. I think this car is beautiful, the engine and transmission are strong, the ride is fantastic, always, always getting complements on its looks, but the electrical engineering is far from that of any other class of car in the market today, or yesterday. And BOGUS messages from the loop control system are a slap in the face to the heritage of this vehicle. They just got it wrong, way wrong.

I've cleaned and fixed all the air leaks one at the throttle body and one at the manifold intake. Replace the spark plugs, cleaned and reset the all the coils, and tested for air leaks. My windshield wiper stopped working. Disconnected the electrics and tapped the control modules, and it started working again - how hookey is that? Which tells me that who ever designs the electrics for this 1999 xj8 must be the alumni from the same class of the 1985 JX6 engineers! Two years to find a problem? That is very telling. It's no longer a passion but an obsession my friend.

The battery fix sounds like a good solution and in worse case I can end up with two good batteries. But folks in here spend thousands of dollars and hundreds of hours, never to find the needle in the hay stack. Thank you all for the advice and I will post my results. Did not mean to cause ire amongst this group of passionate folks, my apologies if I have.

Best regards,

nzane

 

Yeah, it would come on... go away for months... come back on... go away for weeks... then it was just staying on... I went thru the ENTIRE intake and checked the seals, the DEALER smoke tested it... charged me $300 for a stupid rubber seal that DIDNT fix the problem... I had to make my OWN intake and only then has it stopped.

Its not my fault you had a **** car with Portuguese electronics... mine runs fine electrically.

 

Hey, I had a 1985 XJ6 for 13 years. I'd still have it if the tin worm had not eaten it up. Best car I ever loved.