So this is the second time this has happened. So had a miss fire previously which was diagnosed as coil pack. Same symptoms on another cylinder now nearly a year later. Code reader just says miss fire cylinder 3. So replaced the coil pack with Oem part.Drives great for a while then the miss fire returns, engine goes into limp home mode. I can clear the fault and it’s ok for a little while then goes again. Is this likely to be spark plug? These were replaced 20k miles ago and are meant to last 60k miles. Or do I just keep replacing parts until I get to the faulty one?

Unfortunately most of the members on Freel2 have the diesel.

To answer your question there are many factors that can cause a misfire

Here are a few items to consider

0. Anything special about when the misfire occurred, Hot Day, Empty fuel tank, going up hill, did the check engine light flash (it should when the misfire occurs), Hot restart, anything?

1. Spark Plug fouling - Mark the extension with the side facing the intake Valve, transfer the mark to the plug and take a picture of each plug (Do you add oil between changes, this check is to see if your plugs are getting oil fouled) Note: spark plug #6 would be most sensitive to oil fouling

2. Spark Plug change interval - I change mine every 50,000 miles and I use Denso Iridium Spark Plug. Part # IKH20

3. Battery age - Its hot where I live and I replace my battery every 4 years, How old is your battery?

4. Fuel pressure sending unit - the ECU uses this sensor to run the fuel pump (the system doesn't have a return)

5. Capacitor on the wiring harness for the coil packs - a failed cap can cause problems

6. Crank shaft position sending unit - this sets the timing for the spark

7. Relay for fuel pump module - intermittent connection will cause problems

8. Fuse for fuel pump module - intermittent connection will cause problems

9. Failed Thermostat can cause over heating and broken coil packs (I replaced mine due to things that I read on the Volvo boards)

10. Wiring for the fuel pump has a Technical service bulletin for certain years

11. The transfer pump in the tank can be faulty

12. The fuel pump module can be faulty as well


Does your code reader have PID information?

Did it store information about the misfire condition?

Good Luck

Paul

Here is a link that may be of help to you

Note: its a long post with a lot of information

The one thing to remember is that I don't think that the discussion shown below includes a coil failure. (but any of the things discussed in this post could be your problem)

https://landroverforums.com/forum/lr2-35/2...491/page5/


For a coil failure I would direct you to this link

The solution was to replace the Thermostat

http://www.volvoxc.com/forums/showthread.p...-2009-XC70


Good Luck

Paul

Hi Paul,

Thank you for your advice. MIL does flash. Error codes are P0303 and P0353, relate to engine misfire cylinder 3. I have changed the coil pack which has improved things as has adding Redex, but it still happens. Sometimes coming off a motoway into stop start traffic and some times on start up. It even happens crusing at motorway speeds. I do think changing spark plugs would be beneficial. I will keep investigating

Kind regards

Clive

Clive,

You mentioned that you replaced the plugs 20,000 miles ago

Which plugs did you use?

For me personally I used the plugs recommended by Volvo (the primary user of this engine)



Another thing to consider is the fuel.

It is possible that an injector isn't functioning properly.

You could disassemble the fuel rail and swap injectors (2 to 3 for example)

If the injector is faulty then the misfire will move to cylinder 2.


One caution the misfire events are very bad for the catalytic converter.

I recommend fixing it as quickly as possible.


Also don't forget that a failed thermostat has been theorized to cause increased temperature and coil pack failure.


Good Luck

Paul

This is driving me mad. I have changed the plugs for genuine Land Rover plugs. I have changed the coil pack twice and it is intermittent which makes it worse. Today no problem but couple of days ago the miss firing was really back it was not drivable. Being disabled I really need my car

Clive,

You are on the path to finding a solution, don't give up

Items completed so far

1) new spark plugs

2) replaced coil packs on the misfiring cylinders


Recommended next steps

3) Replace the fuel pressure sending unit

4) Keep the fuel tank half full or more (fill it when it gets to half)

5) Clean the MAF with an appropriate cleaner


Reasoning behind the changes

The fuel pressure sending units are known to fail and the ECU uses the sending unit to control the pressure at the rail

The fuel tank has two halfs and it uses a pump to transfer fuel, if the transfer pump isn't working then you can get a misfire when you get below half a tank.

The MAF may be malfunctioning and confusing the ECU and causing misfire


My recommendation is to start with these three and see if you still have the misfire

Good Luck

Paul

Frustrating thing is that this os intermittent and only on cylinder 3.

Clive,

The only evidence that I've found of multiple coil packs failing is due to a failed Thermostat.

The Thermostat in the 3.2 is known to fail at about 10 years

Before you replace the thermostat check the connection on coil pack number three, make sure that all of the contacts are in the right place and not damaged.


Here is the link that shows a volvo owner with the 3.2 had multiple coil pack failures due to a broken thermostat

http://www.volvoxc.com/forums/showthread.p...-2009-XC70

This link shows why a failed thermostat can cause over heating

https://www.matthewsvolvosite.com/forums/v...mp;t=86205

And here is the FREEL2 link that shows how to replace the thermostat

http://www.freel2.com/forum/topic32245.html


Good Luck

Paul

Hi Paul,

I dont know if it does have baring, but thermostat was replaced a year ago. The engine oil cooler ruptured micing oil into the cooling system. New radiator header tank thermostat ecery coolant hose and several days of cleaning all the water ways by the garage. The csr was not left to over heat and even now the temp gauge still doesnt go above normal. All genuine LR parts were used. I will get the thermostat changed as it is possible some gunk my still in the cooling system.

Thank you for all your help

Clive

Clive,

A Volvo owner with the same 3.2 as our Land Rover fixed his Miss-Fire by replacing the MAF.

It may be worth considering

Here is the link

https://www.matthewsvolvosite.com/forums/v...mp;t=87918


Good Luck

Paul

PS not my suggestion, the recommendation came from a mechanic that works on a lot of 3.2's

Thanks Paul. Misfire not as bad but still occurs. Recently it has usually happened when ciming off A road or motorway into stop start city traffic. However if I start and drive round in city traffic all day it doesnt misfire. It still misfires at other times just not as frequently

Clive,

Which cylinders do you get the miss-fire on?

Let me know if you replace the MAF.


Take care

Paul

Hi Paul,

Cylinder 3

Thanks

Clive

Hi Clive

I recently had a misfire on cyl 3 (P0303). My engine is different from yours though (i4 turbo petrol - USA spec) so comparisons may not be wholly valid. Since the incident (my wife was driving) I have driven the car for a week - different kinds of driving - but the issue seems to have gone away (for the time being....). I spoke with my independent specialist and his bet is that the coil is going out. A single coil is relatively cheap so current plan is to install a replacement coil & hope this addresses the issue. Of course I saw your difficulties and was wondering if you ever got to the bottom of the issue? eg change the MAF etc....

Thx
Jim