I decided to start a new thread, because the previous one (https://www.jaguarforums.com/forum/x...-engine-67455/) didn't bring any answers to my question, the title sounded a little tricky and it became too long with just repeating one and the same issue.

The problem is that the engine is not working properly when starting the car with cold engine at temperatures lower than 10C. The car is shaking at P and N, but when I try to switch to D or R, the car barely moves. If I step on acceleration the engine is working as there is not enough fuel - a huge amount of air is entering the engine, but the amount of fuel is not enough and so the engine "chokes". This is the reason why the car doesn't want to run when and it's getting worst as I try to accelerate, but if I leave the car without touching the pedals it moves, but very slowly. Ones the car reaches 2000 RPM or if left on idle for about 2 minutes it magically fixes... it doesn't demonstrate any kind of problem after that except little shakes on idle (almost impossible to be noticed) - lets say it works like it's not V8 but an old 4 cylinder line engine The most important thing is that the problem is related to the outside temperature of the air!!! If it's hot enough - there is no problem while in the winter at -20C I was almost unable to move the car.

So the question is - what could be the problem. There are no errors - neither on the dashboard, neither trough OBDII. Spark plugs are new NGK, the air-filter is clean, the part load breader is clean, throttle body is clean, as well as the throttle body connectors. The only known issue is the cam cover gaskets which I'm about to change this week. The fuel pressure is at normal levels.

The main suspects are the MAF and the Throttle position sensor, but I don't know how to confirm where is the problem, because when checking values from the MAF they seem to be normal and the throttle body butterfly is responding normally when I step on acceleration.

The newest issue which I believe is directly related to the mentioned - I have a very low mileage when driving on highway or outside the city. The urban fuel consumption is 16/100 which seems normal, but on highway it took 14/100 with cruise control set at 120km/h for more than 250km distance with only two persons inside, without A/C, without any kick-downs... And the worst scenario was the last weekend when I've got 18/100 when driving to my birthplace with 5 persons in the car with no more than 90km/h at night with absolutely no traffic for more than 400km.

 

Unmetered air leak by the sound of it. Try a new set of intake manifold gaskets and throttle body gaskets (both sides) can you get your hands on another MAF?

 

I know it sounds very "home made" but we've tried to wrap with tape every part which could suck air from the air filter box up to the throttle body - no change at all.

I really believe that it's the MAF... the problem is that here in Bulgaria is very difficult to find another XJ and even almost impossible to convince somebody to share any part of it for test on another car And the MAF is not such a cheap part to be order only to check if the old one is working or not

 

Is the MAF clean?

Maybe you should concentrate on fixing the reading of OBD2? That way you could at least read LT/ST fuel trims.

 

I forgot to mention - the OBDII is working well. I already have OBDII scanner (ELM327 v.1.4) so I can read any data. I'll make a log of the values for RPM, MAF and LT/ST fuel trims and post it back here

 

Well as strange as it sounds - I think the mysterious forces around the car did their work once again -> the problem suddenly just disappeared.

What actually happened -> I left the car at my mechanic's workshop for changing the cam cover gaskets. He did it and after then the engine starts at cold as smooth as never before. I'm thinking about the problem I had over and over and I can't find any relation between cold starts and the cam cover gaskets!!!

Even now when the cold start problem is gone, the car is still shaking lightly at N gear. Maybe it will need a little more investigation.

P.S> I tried to read the values from the LPG computer and I found that the values from the Lambda are changing all the time between to reach and to poor mixture. Is it possible or it's some kind of bug on the LPG ecu? What should be the values?

 

Unfortunately the problem appeared again... it skipped the summer (maybe because of the hot weather) but now, when the temps started to drop at the morning - the car's idle on cold start is unstable just like before.

So it seems that "problems just doesn't fix by themselves"

The only good news is that FINALLY I managed to catch the problem on video with my phone this morning.

Here is the link to youtube with the uploaded video:
Here is some information about the conditions when I start the car:
- I always wait for about 10sec after turning the key on ignition before starting the engine;
- The temperature outside is 9C (48F) and the car was left for about 12 hours for the whole night.

I'll explain what's happening and what I'm doing on the video:
(0:00 - 0:14) - waiting before starting the engine;
(0:14 - 0:16) - starting the engine;
(0:16 - 0:19) - after the start the engine RPM's goes up to 1100 and then immediately drops to 500 (I don't touch anything at this moment);
(0:19 - 0:35) - I left the car working... it seems that the computer of the car is trying to stabilize the engine work;
(0:39 - 0:45) - I'm starting to step on acceleration;
(0:45 - 1:06) - each time I touch the acceleration pedal the RPM's are dropping. Each time I'm doing it harder;
(1:06 - 1:08) - When the RPM reached 200, the Check Engine light appeared and the computer said "Low oil pressure" I decided to step almost to kick down. This is the moment when I managed to rev the car normally up to 2000-2500.
(1:08 - the end of the video) - the engine starts working absolutely stable like it should!

The thing you can't see on the video is how the car is shaking and the sound of the engine.

Any suggestions what could be the reason for this!?

 

Is this on gas or lpg?

If on lpg, is lpg known for rough cold starts?

 

Basically all lpg systems have a configuration regarding when to switch between lpg and petrol.

In my case the system expects 2 values:
- 40C temp of the coolant system;
- at least 2000 RPM to switch once from gas to lpg.

So in this video the car is running only on petrol... I was thinking to try force start of the car directly on lpg, but it's a bad idea because the lpg evaporator can easly freeze because of the low temperature and this will bring to a very huge failure of the entire lpg installation.

 

LPG is a propane/butane mix and the fractionation will vary with temperature - colder = less butane.

 

There are two main suspects at this moment:
1. MAF
2. TPS

The problem is that here in Bulgaria there is no way to find a MAF from another XJ8 3.2 just to test if the problem will disappear... and buying a new MAF only to check is kind of expensive + a long period of waiting for delivery
So the only way to check is reading the data from the sensor. I do have an OBDII to USB cable with software for reading live data, but I don't have the default values. I found this one: JagRepair.com - Jaguar Repair Information Resource but there is information only for 4.0l and 4.2l engines...

So my questions are:
1. Can anyone tell me the reading from 3.2 V8 engine for MAF, as following: Park idle, Park 2500 RPM, Drive idle, Drive 1500 RPM?
2. Is there any way to check if the TPS is giving normal values!?

 

You can do static tests with a ohm meter. This would show you if you have worn or dead spots in the potentiometers. The specifications may be in JTIS.

You should also check your tps connectors for material type as there was a service bulletin regarding material mismatch. Gold conductors on one connector and tin on the mating connector. That causes problems. See SuperSport's recent post from yesterday to find the TSB and his alternate solution.

 

Well it seems that I managed to fix the problem... here is what happened:

As I mentioned in another thread - I had problem with engine oil loss... I found out that the reasons for that are two: valve seals and a mistake I did while cleaning the part load breather - I accidentally drill the metal shield under the cam cover. So yesterday I decided to open the cam covers to fix these problems. While doing this I had to take out the spark plugs and found that they were burned out on the outside (on the light side)... Something like this but much worst:


The strange thing is that the spark plugs are not old - I installed them around 4 months ago (about 10000km). I suspect that they were not original NGK iridium but maybe some sort of Chinese fake plugs...

After fixing the part load breather and the new spark plugs the car started to work just fine... at least for now I'll keep you in touch.

 

Good luck, let's see how it goes

 

looks like corona staining on that plug...

 

Unfortunately bad... after a very nice Europe trip with about 5000km for two weeks with the Jag, now I'm back in Bulgaria and the old problems started to appear again. I'm talking about the issue I've managed to capture on video that I posted few weeks ago - on very cold start the engine is working unstable and when I try to step on acceleration the RPM's are dropping or just not increasing... In the last two days - even stepping on kickdown the car didn't move at all keeping at 900-1100 RPM. Once I released the acceleration pedal it reved up. This time I even managed to hear what is the knocking sound coming from the car while this problem appears - these are detonations in the exhaust because of unburned fuel...

So the question is again WHAT'S HAPPENING? Again the main suspects are the MAF and the TPS, but I still can't explain few things:
1. The throttle is mechanically connected with the pedal inside the car... So when I step on kickdown the butterfly in the TB should be 100% open! Why the RPMs are not moving?!
2. Why everything is related to the magical 2000 RPM that fixes all problem in just a second!? What's happening under the hood when I manage to increase the revs...
3. Why the problem appears randomly... sometimes on very cold weather it works fine, sometimes it happens on hot sunny days...

 

No it isn't. Read up on throttle position sensors and OBD.

 

Have you cleaned the MAF sensor?

I could not find a procedure for this here, but did find an interesting article on another site that may be relevant:

Cleaning the MAF - solving overdrive problems

Also for a diesel jag:

JX Inf MAF Sensor Clean.pdf -- June 6, 2011 6:11 pm -- 803k

Anyway, it seems cleaning the MAF sensor should be pretty easy.

The 2000rpm "fix" may be related to the LPG cutting in?

 

I'll try to read the data through the OBDII to find out what is showing as values for the TPS and post it...

Also will do a new cleaning of the MAF, as I once did it an year ago...

Nope, it's not because the LPG computer is always waiting for 40C temp of the coolant system to prevent the evaporator from freezing.

 

From which sensor? Maybe the sensor is faulty. Try shutting the LPG valve manually for a test. Or maybe, the LPG solenoid valve is faulty and sticks.