Outside is -3C (26F) and you expect the engine, after a cold start, to be able to increase the temp in the engine bay up to 25C (77F) for about 2 minutes - that would be one hell of a good heater over there The only way to do that would be splashing fuel over it and burn it out which is not such a bad idea after all problems I'm dealing with...

 

Never measured it fromcold, but the intake temp does rise quickly when standing still. Let’s hope youhave found the fault as it indeed sounds like a quick raise in temp, and assaid a new MAF isn't bad to have anyhow.

 

Fingers crossed here, it's been going on far too long! I'm certain the MAF was suggested months ago, but difficult to source in your country.

Good luck with it

 

Didn't had time to write about this lately... but unfortunately it's not the MAF - I've installed a new one and the car is working just like before on cold starts. I decided to check everything I can so I asked a friend of mine to try and find me, just for a check, some parts. So I tried replacing: throttle body and fuel pump - no change. After that I decided to clean the injectors - same...

So now I'm stuck on a dead end - I have no idea what could be causing the problem

 

I have been following this thread with interest and it is terrible news that you have still not been able to solve the problem. I am not qualified in any way to make suggestions or formulate an opinion from training or experience but is it possible it could be a software problem?

It does sound like a fuel/air mixture issue and if you have changed all the mechanical parts relating to this, then the brain seems to be malfunctioning.

I believe when you try to start a cold engine on full throttle, the fuel is cut off to prevent damage from over revving and I wonder if this system is somehow kicking in to starve the engine of fuel.

Not a clue how you check or solve a brain problem though.....

 

Just to chip in, I have the same problem.

I have only had the car a couple of weeks, but it does the same cold-shudder-start and no power on drive for the first couple of minutes. Interestingly mine (like yours and the other person that reported the same problem) runs on LPG. This may or may not have anything to do with it, but it is a pattern.

Now my XJ8 has 178000 miles on the clock so I really wasn't expecting it to be perfect. I have checked all the basics that you can without software or specialist equipment and all seems well so I am also at a loss. Nice to know I might not have to suffer with it in the summer though!

Let us know if you have any breakthoughs!

 

Webbi as I mentioned many times - I'm 100% sure that this problem has nothing to do with the LPG... First of all - I had this issue even before installing the LPG system, but it was less noticeable and I didn't pay attention to it. In time it became so rough that when it's cold I must wait at least 2 minutes at idle before running and almost every first 500m are just hell to drive. Second, regarding the LPG - this winter I decided to almost completely remove the installation and the problem was still there with no change.

After many many diagnostics I did now I'm sure that the problem is the mixture of fuel and air. As I'm pretty sure I hear "detonations" in the exhaust it seems that the mixture is too rich and the fuel is coming out the engine unburned. The throttle body is opening normally meaning that the needed air is flowing in, the MAF is new, so the computer should know how much air is entering... What else is responsible for the mixture? Something which work depends on outside temperature and that changes its values after the car reaches higher than 2000 RPM... something the doesn't mistaken the idle work of the engine, but does confuse the mixture when trying to accelerate

That's all I know...

 

Estilian I know you mentioned that you thought it was nothing to do with the LPG, as did the other poster, I merely mentioned it was a pattern is all. You did investigate the LPG to begin with, no? Anyhow, as you are running with petrol now it shouldn't matter.

I can definitely hear the 'popping' from the exhaust if I put my foot down soon after the cold start, with no real power moving the car unless I am foot to the floor. I was going to investigate an unmetered air leak as my first suspicion, but I am very glad you have documented all your efforts so far as it has given me a good guide on where to look.

I think it is worth noting that the idle is fine on the key turn and while the revs are around 1000 rpm, but after the revs drop the problem begins to make itself known. I am new to the Jaguar so have no idea about the choke system it has but could that be something to do with it? Just shooting ideas out...

 

Well a little update over this topic... I decided to check all coils. I couldn't find 8 new coils but only one so I started replacing with it each one I had installed. The problem is that this procedure took me about two weeks because for each change I had to test at cold start. No luck with that as well - the engine is still randomly shaking at cold.

Any update from someone?

 

coolant temp sensor ok?

O2 sensors ok?

 

3 months later - back to this subject AGAIN I was abroad for a while and now I'm back in the garage together with my beauty

The problem is getting worst - now the engine works unstable at cold start even when the outside temperature is very hot. The only difference now is for how long it will last - if it's cold outside (10C or 50F) it takes the car about 1-2 minutes and it's almost impossible to run the car meanwhile... the engine never stalls during this period of time but I barely manage to increase the REVs to more than 1100... as before - if I step on acceleration the engine is "choking" and the REVs are actually dropping, no matter how much I try to accelerate. All this time the car is shaking enormously. The solution - each morning I wait for about 1-2 minutes for the engine to warm up.
If the temperature outside is higher (28-35C or 82-95F) the problem appears only for the first few hundred meters or 10-20 seconds. Again, as before - the easiest way to overpass the problem is to try increasing the engine REVs to more than 2000. Once reached the engine starts working normally, but ONLY if it's driving... if I'm on parking and REV the engine - nothing changes.

To summarize what I tried already and it's not improving the situation:
- New MAF;
- Another throttle body;
- Checked the entire plastic tube from the air filter up to the TB for cracks;
- Fuel pump.

Obviously it is either the air volume, air-intake temperature or the mixture of air and fuel! As much as I know, when you start the engine after a long stay (meaning it's cold), the entire engine system is working in a "special" state, reading just a few data. Obviously the problem appears exactly during this stage...

One friend from the forum has suggested to try adding a resistor to the MAF's cable changing the data for the air-intake temperature... and he mentioned something about IATS, but I really don't know what is that.

Any new ideas?

As for the Sean's question - no, I haven't checked the coolant temp sensor, but I really don't see any relation between it and the problem... Besides - when I was reading live data through OBDII the coolant temp seemed to be right.

 

Hi Estilian, I commend your staying power and the way you methodically test things out and record the findings - Since you changed the MAF, have you checked that the temperature values returned in your previous tests (28 degrees) is now correct or still the same......This could still be the problem until you can confidently take it out of the equation.

Did you do a compression test on each cylinder on the cold engine? and repeat the compression test with oil in the bores if low values on some cylinders - What were the results....? Are you getting any fault codes for ignition? or anything else...nothing at all?

For what it's worth, I would repeat the pages of readings that you did previously -that is let the data tell you what the problem is - if they are all correct (double check and validate what the 'correct' values should be) and if you still have the problem perhaps look at the throttle position sensor (I think it's on the Throttle body?) Crank position sensor? Knock sensor - do they have one? start moving out - I get a feeling its a sensor/input or an air leak - I'd prove or eliminate the cylinder condition as it's a straightforward test if not done already - I hope the data from your readings will highlight the problem............I hope this helps....Allan

 

After so many months searching for a solution, I finally found the reason for this problem... A friend suggested something that appears to be source of the unstable work at start-up - he explained to me that the engine works a little bit different on LPG than on petrol and readings from the oxygen sensor (the lambda sensor) are not correct... when the engine is working on LPG the mixture is more lean because it burns at higher octane factor (apprx. 105 vs. 95-98 on petrol).

When you try to start your car after a long stay the ecu is using the last data from the lambda to prepare the mixture... and because the engine was working on lpg, the data is wrong for petrol!

How did I found it? I just left the car run only on petrol for a month and did a hard reset... now the car is working perfectly!

Now I have to talk with a few experts on lpg to find a solution... how to pass to the oxygen sensor a proper data readings even on lpg.

 

I have been following this post for months and am so glad you have solved this mystery.

Your friend is an ace!

Many people suggested it must be something to do with LPG but this is clearly a new one that should help others, especially if you can now find a solution to the computer programming. I am surprised that the LPG system manufacturers had not taken this sort of thing into consideration.

Damn computers.....