It's reading through the OBDII the temp of the coolant. But I really can't see any relation between the problem and the LPG... At least because the issue existed even before I installed the gas

 

Sorry Estilian, didn't see previous post.
Check that the car is actually starting on petrol.
Check fuel pressure.
Set your obd reader to record ltft and stft from startup, it may be that the ECM has decided to set fuel trims to minimum because you are running on gas most of the time. The O2 sensors aren't used from cold, takes about a minute for them to warm up.
You could try a bottle of fuel injector cleaner, they may be partly blocked due to lack of use.

 

Hello, I do have the same problem with my XJ8 3.2 '98
Does someone has found a solution for this issue?
I already changed MAF, Throttle Body (with TPS), Spark plugs, Lambda's, Clean air filter, ...
My car has the same configuration on LPG as Estilian.
I think i noticed this problem before LPG installation ...

 

As the weather is getting colder (-10C at morning) the problem is more and more noticeable. Now I can define what's exactly happening:
When I start the car the RPM's are stable, keeping on about 1000-1100. If I accelerate without moving the car (just increasing RPM's on parking) the engine acts perfectly. No noises, no shakes, nothing.
When I switch to Drive or Reverse the car starts moving slowly as it should, again without shakes or interruptions. The problems start when I touch acceleration pedal. As much as I step on acceleration as worst it becomes - the RPM's are dropping down instead of increasing. If I try to step down to kickdown sometimes it even stalls the engine. Apparently the engine is taking more air than fuel or vice versa...
This issue disappears when the car warms up (when it's not so extremely cold it's enough to increase once the RPM's up to 2000).

For the past few weeks I managed to find a way to drive the car with this problem on... I noticed that if I touch gently the acceleration and than release it the car is first slowed than it moves and increases RPM's. So I repeat this procedure 4-5 times, giving more and more acceleration each time until it starts moving with more than 1800 RPM, than I just keep the speed and for about a minute it's ok.

It's important to say that because of the low temperatures (sometimes reaching -20C) I've stopped using the LPG on the car. So now the car is working only on gasoline without any changes. Meaning that this problem has nothing to do with the gas

 

For me it looks like the fuel pump is coming to death.
It may provide the normal pressure, but the volume is quite low. Check if the fuel volume, provided by the fuel pump is normal.
Actually you can install a fuel gauge (they are also available with the volume metering) and drive the car. Check for the pressure drops before the engine stalls and check the volume. Another option is to check is there any fuel in the rail RIGHT after the engine stall (but you should turn the ign.off right after the stalling).
Also check the air temp. via OBD-II, check the MAF readings and LTFT/STFT. If you are able to make a trip log with android torque app. or any other similar it will be a great help. (LTFT/STFT, MAF, air temp, coolant temp, measured AFR, ign. advance, RPM and fuel flow)

Also, such a problems may be caused by a clogged fuel filter on a fuel pump or clogged injectors. This is a common fault for a LPG vehicles, rust builds up in their tanks...

 

This is a long time to have this problem.

Apart from checking and posting all the readings that the guys have asked for.

Make a check on what you actually have in your petrol tank.

Over time and normally running on LPG 'could' cause stagnation and water/condensation build up, not good for any part of the system.

Especially at -20C overnight.

 

I will check the fuel pressure, but what's the explanation why the problem disappears when the car is warm?! Same for with clogged injection... the problem would exist even when the car is in working temp and would have problem in high RPM. So I would bet on intake temperature.

Translator, as I said, for the last month I'm driving the car only on petrol so I already changed like 3 full fuel tanks. It couldn't be related to fuel quality... Besides when I was installing the LPG I asked the mechanics to leave the fuel pump working constantly so there is always fuel passing though injectors to keep the clean.

I'm expecting a new OBD reader next week so I'll be able to do a more detailed log of the different data.

 

Warm engine req's much less fuel... So the bad pump may be able to provide that amount - for a while Quite a usual thing in my experience (5yrs as a mechanic, 2yrs as a GM Academy trainer, 2yrs as a JLR Russia trainer)

 

Can you tell me what pressure should I expect?! Tomorrow the cat is entering my mechanic's garage so I'll ask him to check to fuel lines. The engine is 3.2 V8 from the early models.

Спосибо за помощь

 

I'll look in a JTIS a little bit later today, when i'll be at home. You'll need to check not only pressure, but the volume too.
Just in case i can give you my phone nr., so you can call me (i speak english and russian ). Skype is ok too.

 

~38psi @ idle
~44psi @high rpm or with pressure regulator disconnected
and AT LEAST 110 liter per hour of volume. You can check it if you'll short-wire the fuel pump relay and check the flow @ the schredder valve on a fuel rail.

 

Well this weekeng I found the worst thing a Jag owner could ever find... that my cat's engine is dying. Since the first day I have my XJ I was planning to check the compression rate of the engine, but never had the chance to do it or most of the time I was just forgetting. Well - I did it... and it showed up terrible values:
Left bank: 9 / 7 / 9 / 7
Right bank: 10 / 8 / 9 / 8

At this moment the engine is still starting even on cold from the first try, but maybe it will get worse soon. I even saw that it's blowing from the dipstick whole...

I guess this explains the low mileage mostly on extra-urban and highway which is almost equal to my urban fuel efficiency

This is also explanation why the car is burning oil even after changing steam valve seals and why it's blowing oil from both part load breathers even after rebuilding them

Now the only question is - what should I do now?! Is there any way to rebuild my compression somehow?! As much as I understand this is early nikesil problems and there's almost nothing to do except changing the engine, selling the car, braking it apart or smash it in wall and take the insurance

As for the problem we were discussing earlier - I checked the fuel pressure. It's just perfect:
- 2.6 bars on idle;
- between 3 and 3.1 bars on high RPM.

Besides I noticed a fuel smell from the exhaust when the problem is unstable... so the mixture is wrong, but it seems that the fuel is more than the air. At the beginning of next week I'll receive my new professional code reader and will check the live data to see what's wrong.

 

As for the compression readings - try to doublecheck the compression as follows:
--First run
-Engine is warm
-Throttle is 100% open
-Battery is fully charged
--Second run
-add some oil (~10ml) into the cylinders and check again.
If the compression builds up with oil - it's the sign of the problems with the liner. If it stays almost the same - time to do the valve job

As for the fuel smell: check the measured AFR and LTFT/STFT. You can do it even with ELM-327, no need in professional OBD-II reader.

 

Go to my next reply as the forum doesn't support tables so they don't appear as I expected

Data on warm engine with rev-up on parking without moving the car:
Load_PCT(%) 19.6 19.6 20.0 18.8 18.0 16.9 15.7 16.1 16.9 16.5 22.0
ETC(C) 90 90 90 88 86 86 85 85 86 86 86
SHRTFT1(%) 1.6 7.8 4.7 8.6 0.8 8.6 0.0 -1.6 -1.6 0.0 5.5
LONGFT1(%) 0.0 0.0 0.0 0.0 2.3 1.6 3.1 3.1 3.1 3.1 2.3
SHRTFT2(%) 2.3 8.6 4.7 6.3 0.8 3.1 0.0 3.1 3.9 0.8 -6.3
LONGFT2(%) 4.7 4.7 4.7 4.7 7.0 4.7 6.3 6.3 6.3 6.3 7.8
RPM 670 679 673 1158 1502 2086 1741 1561 1728 1848 675
Speed always 0
Shift always Parking
IAT(C) always 29
MAF(g/s) 5.21 5.05 5.39 7.15 11.70 12.49 11.98 9.60 10.41 11.30 4.66
TP(%) 2.7 2.4 2.7 3.9 6.7 6.7 6.7 5.1 5.5 5.9 2.0
SHRTFTB1S1(%) 4.7 4.7 4.7 9.4 0.0 3.1 0.0 -1.6 0.0 -5.5 -3.1
SHRTFTB2S1(%) 4.7 6.3 6.3 3.9 2.3 0.0 2.3 0.0 2.3 -5.5 -3.1


Data on warm engine while driving:
Load_PCT(%) 27.1 36.9 23.522.4 36.9 40.0 39.620.8 38.8 25.9 18.4
ETC(C) 88 90 90 90 90 91 91 91 91 91 91
SHRTFT1(%) 7.8 4.7 5.5 2.3 10.2 9.4 10.9 1.6 8.6 5.5 0.0
LONGFT1(%) 3.1-6.32.32.3-6.3-6.3-6.30.0-4.73.13.1
SHRTFT2(%) 10.24.72.33.911.76.34.74.710.26.30.8
LONGFT2(%) 6.3-3.17.87.8-3.1-3.1-3.13.9-3.16.36.3
RPM 1333 1696 895 763 1548 1578 1540 1227 1636 1358 1235
Speed (km/h)726271128414952555654
Shift always on D
IAT(C) always 27
MAF(g/s) 18.1222.257.4713.8923.8823.6220.888.5311.8111.358.93
TP(%) 10.612.94.39.813.713.711.84.36.35.94.7
SHRTFTB1S1(%) 3.910.92.39.411.74.73.90.86.3-3.11.6
SHRTFTB2S1(%) 7.03.92.33.912.511.74.70.89.41.66.3

 

Here is what I got today on warm engine while the car was on parking and after that - driving around. The car is running only on petrol, no LPG at all. The engine was working as it should - no shakes, no smells, just perfect! Tomorrow morning I will post similar data but on cold start.

Does anyone see something wrong with this data?!?!

Data on warm engine with rev-up on parking without moving the car:


Data on warm engine while driving:


P.S> I just noticed a little mistake from the diagnostic software... the second LONGFT1(%) is actually LONGFT2(%)

 

Best measurements are always once you have let the stft/ltft values stabilize.

So do an idle measurement, wait until the figures are stabilized and then take a measurement.

Next also one for driving, i.e. 50mph, drive steady, wait until the figures have stabilized somewhat, and then do a measurement

 

Thank you for the advice avos - will do the measurement again. Which values from the table below should I record on my scanner?

As for the different conditions, I will do the following tests for both warm and cold engine:
1. Idle on parking
2. Idle on D with brakes
3. Running on D without touching the acceleration
4. Driving with 30mph

The problem is that the unstable work of the engine appears only while trying to accelerate for the first time after a cold start... Once I reach 2000RPM the problem disappears so there is no way to record data with stabilized values in this condition Any ideas what to do?

Today isn't so cold (about 5C) so I decided to try to start the car directly on lpg, without even passing through the petrol... to see if the problem will appear as well. If it does - then it's something related to the air... if not - it something with the fuel... maybe pump or injectors. Will report later the results!

 

Well the circle is closing... Now I'm sure that the problem is related to mixture and the main suspect is the air... so it's either throttle body or maf! I confirmed that by starting the car directly on lpg without even using any petrol the engine is acting in the same way as before... so it's not something with the fuel pump, injectors or anything else...

The only thing that's left is to find a way to check which one it is... or maybe something different?!?!

Yesterday while reading my old threads I realized that I have this problem for an year and a half described in different ways in 4 separate threads:
https://www.jaguarforums.com/forum/x...ke-half-63224/
https://www.jaguarforums.com/forum/x...t-start-62751/
https://www.jaguarforums.com/forum/x...-engine-67455/

This weekend I will spend little time to measure values as avos suggested... but still - can someone confirm which of all the values from the table above I need to measure?!

 

FINALLY - I FOUND IT It's the MAF sensor...

Here is what happened. Last Sunday (I tried to post a reply from my iPhone but something was wrong as it appears that my reply is not here) was again a very cold morning so I decided to run a new reading with my OBDII scanner. So I entered my jag, connected the OBD and started the engine while watching the data on the tool. I set the tool to show all available data from sensors to be sure that I'll capture if there's something wrong... and it was! The engine ran just as I expected it to run - first the rpm's increased up to 1100-1200 then in just a 1-3 seconds it dropped to 800 and then the car started shaking... then I tried to step on acceleration pedal - each time I was accelerating, the rpm's were actually dropping down... even when I stepped up to 30% of the way of the pedal the car almost stalled at 200 rpm's. So here is what I saw on the scanner tool:

As the sensors are too many to appear in one screen it's separated on few pages. The first page was for temperatures... Everything seemed ok at first look - coolant temp was 0, air intake temp was also 0 and the outside thermometer on the A/C dash was showing -3C degree... so it had to be normal.
Second page... fuel trims... to be precise: SHRTFT1, LONGFT1, SHRTFT2, LONGFT2, SHRTFTB1S1 and SHRTFTB2S1... Here is the place to mention that I don't have even a single idea what does short and long fuel trim mean. But I was confident that there's something wrong with it as all 6 sensors were showing constant 0 except the LONGFT2 which was stable at 6.1% at idle, then in a few seconds it dropped to 4.5% at idle. When I was stepping on acceleration the value was dropping down to -3.2% while just for a second a value of 2.1% appeared for SHRTFT2. All other sensors: SHRTFT1, LONGFT1, SHRTFTB1S1, SHRTFTB2S1 was stable on zero both on idle and while trying to accelerate.
What does this mean?!?!
Third page was throttle position, MAF, RPM's and others... Here I was confident that I'll see if there is any problem with my throttle. At idle the position was stable at about 3.4% and the MAF was showing 4.8g/s... when I was stepping on acceleration the TPS increased up to 33-35% and the MAF increased up to 40-50g/s. So apparently it was responding to my foot No problems as much as I understand.

Than the payoff came! I scrolled back to page one, just to recheck data and then I saw it... it was the IAT(C) - air intake temperature... it was already at 28C degree and it was increasing with one Celsius every 3-4 seconds... As you may except the temperature outside the car didn't changed for the last minute while I was testing... there was 40cm snow all around and over the car! So here it is... The MAF is returning wrong data about the temperature of the air that's entering the engine which is messing up the mixture of air and fuel. And again - as much as I know how the MAF works it's function is based on two temp sensors inside of it and a microscopic heater between them. Meaning that - wrong temperature will be equal to a wrong volume of air entering the engine!
Maybe the problem is present only at cold weather as the difference is too big... and when the engine is hot it's taking data not only from the MAF to calculate the mixture.

I've ordered a new MAF already... I'm expecting it to arrive soon. Meanwhile I want to recheck the strange values about the fuel trims and to learn more about what do they mean

Will keep you in touch.

 

At a certain point the engine is generating lots of heat via the exhaust headers, some will radiate into the intake, and some of the hot air will also find its way into the intake of course when standing still. But another MAF isn't bad to have.