I am chasing a problem with my 2006 4.2SC. It has developed a misfire that has gotten worse. The engine runs very rough and if pushed will go into limp mode. I have a IIDtool, and I get misfire codes on all cylinders, random misfire and misfire at startup.

This is what I have done:

Removed engine cover and sprayed starting fluid everywhere to detect a leak - nothing
Filled fuel tank, soomeone mentioned that this could do a difference for a faiiling fuel pump or a clogged fuel filter - nothing
Changed air filter - nothing
Cleaned MAF - nothing
Cleaned MAP - nothing
Checked hose to PCV - clean and open

Coil packs would be my first starting point? 2012 Orkney Grey Westminster 4.4TDV8 with Ivory interior.........nice!
Alfa Romeo Giulietta
Just one Montesa now, 349 White Wonder
Austin A40 Farina MK2
1975 Morris Marina 1.8TC

I have been thinking about that, but is there anything that can kill all coils? I have checked codes twice, and the only Cylinder that I have not had misfire on is no 3.

I have a IIdtool (not BT), is there any checks I can do with it? 2006 Supercharged

Personally, I would say a misfire is more electrical than fuel........happy to be proved wrong.
I know very little about these petrol versions as I have the TDV8 4.4.
I suppose you could start with spark plugs-leads-coil packs......all depends on the mileage & when these serviceable items have been changed. Spark plugs for instance, I believe, have a 100k miles lifespan......far too long in my opinion.

Just a thought, keep us informed & good luck. 2012 Orkney Grey Westminster 4.4TDV8 with Ivory interior.........nice!
Alfa Romeo Giulietta
Just one Montesa now, 349 White Wonder
Austin A40 Farina MK2
1975 Morris Marina 1.8TC

I have changed the spark plugs, they did not look good, but it made no difference to the misfire.

There are other threads on here about 4.2s and failing fuel pumps. Can anyone confirm that this is the correct part no: LR015177? And, I have not found a fuel filter, is the filter in the pump or are there a separate filter? 2006 Supercharged

I'm going to stick my neck on the block & go with coil pack[s].
What kind of mileage has your car done? If the spark plugs look bad & the car has done in excess of 100k miles, then the coil packs could be well past their sell by date.
There's a guy on here called 'Haylands' who has a 5.0SC & he's pretty switched on, tried sending him a message for his thoughts? 2012 Orkney Grey Westminster 4.4TDV8 with Ivory interior.........nice!
Alfa Romeo Giulietta
Just one Montesa now, 349 White Wonder
Austin A40 Farina MK2
1975 Morris Marina 1.8TC

Thank you, I will try to change the Coils. I have searched and learnt about possible failures and I think that anything fuel related should throw a code.

Come to think of it, might a Cylinder not firing confuse the Lambda sensor into fuelling the others wrong?

Then again, wouldnt the Lambda sendors and engine management create error codes if the mixture fluctuates too much? 2006 Supercharged

Hi Ian

I feel for you.

I went through something similar to this and unfortunately it was a whole range of things I imagine due to the mileage and age.

Do you have a scanner? if ou do you can check if its running really lean or rich ? if lean it could be an air leak before the s/c and if rich it could be an air leak after the s/c.

I tried the started fluid stuff to find it its a no go if the leak is after the supercharger as it will blow it away rather than inhale it.

You really want a smoke test you can pickup a decent smoke tester used fro around £200 if you have a compressor or get a garage to do it for around an hours Labour. If the insert the smoke where the airflow meter would go in will test the intake and crank case which is how we found I had a leak at the top of the supercharger where the two concertina bits go from the s/c to the air coolers, the small hose from the S/c to the fuel pressure switch had blown off (have you checked this its common!) which needed a new pipe as it kept coming off, a leak from the pcv and a leak from the bottom of the oil filler neck. As I say most of those are after supercharger so spraying will not help.

Once fixed it ran a load better but still not quite right and I found I had a collapsed cat. I checked this by laying under the care and hitting it with the end of a fist and you could hear it all rattling. Changed that much better but not 100% - cleaned the man - o change but notice it was original at 110k so bought a new genuine one and wow what a difference! it then was nearly bang on so I thought id change all 4 o2s for good measure and now she is fine except a random running out of fuel at 30 miles range hmmm.

Anyway since doing all that it did have an intermittent misfire on cylinder 4 and 5 I changed the coils it did fix this but I think for all 8 to go at once you are likely looking in the wrong place.

Also forgot to mention I changed the intake fuel filter and ran a can of bg44k through it at some point too

Hope this essay helps! Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

When you filled the fuel tank up did it show it was full on the guage?

Sounds similar to issues I had on my Audi A8. Turned out to be coil packs failing. Because they were the same age they all went at pretty much the same time.

Dunc. The life you have is the only one you'll get; make the most of it.
--------‐--‐-----------------‐------------------‐---------------------------------------------------
2012 4.4 TDV8 L322 Autobiography
2003 TD5 Oslo Blue D2 ES Premium Auto (with mods!)

Thank you for sharing your findings with me, I appreciate the time you spent to decribe it!

I did not realise that there was no underpressure after the supercharger. It feels strange that it can be overpressure there though?

I do have a IIDtool (not BT) but I have not been able to find a menu for live values, maybe I need to look again?

I checked a hose going from the intake to a sensor, probably the fuel pressure switch you refer to, this looked good.

I have 8 coils arriving soon, I will try to change them all, if this will not cure the problem I am going through your comprehensive list!

I have just changed a CAT too, did not seem to change anything either. I hit it and thought I heard a rattle but when I removed it from the car there is really nothing rattling inside so I am not sure it had a problem.

Danwilderspin wrote:

Hi Ian

I feel for you.

I went through something similar to this and unfortunately it was a whole range of things I imagine due to the mileage and age.

Do you have a scanner? if ou do you can check if its running really lean or rich ? if lean it could be an air leak before the s/c and if rich it could be an air leak after the s/c.

I tried the started fluid stuff to find it its a no go if the leak is after the supercharger as it will blow it away rather than inhale it.

You really want a smoke test you can pickup a decent smoke tester used fro around £200 if you have a compressor or get a garage to do it for around an hours Labour. If the insert the smoke where the airflow meter would go in will test the intake and crank case which is how we found I had a leak at the top of the supercharger where the two concertina bits go from the s/c to the air coolers, the small hose from the S/c to the fuel pressure switch had blown off (have you checked this its common!) which needed a new pipe as it kept coming off, a leak from the pcv and a leak from the bottom of the oil filler neck. As I say most of those are after supercharger so spraying will not help.

Once fixed it ran a load better but still not quite right and I found I had a collapsed cat. I checked this by laying under the care and hitting it with the end of a fist and you could hear it all rattling. Changed that much better but not 100% - cleaned the man - o change but notice it was original at 110k so bought a new genuine one and wow what a difference! it then was nearly bang on so I thought id change all 4 o2s for good measure and now she is fine except a random running out of fuel at 30 miles range hmmm.

Anyway since doing all that it did have an intermittent misfire on cylinder 4 and 5 I changed the coils it did fix this but I think for all 8 to go at once you are likely looking in the wrong place.

Also forgot to mention I changed the intake fuel filter and ran a can of bg44k through it at some point too

Hope this essay helps!

Just pmd re cat but I doubt it’s all the coils but intrigued to find out! Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

Thank you all! Today we changed all 8 coils, and now the car is like new again! So, if you have misfire and no other error codes, it is probably best to start with the coils 2006 Supercharged

What mileage was your car? Did you have a slightly lumpy idle before do you remember? How is your idle now? Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

Also did this fix your lamdba/ o2 faults? If you had one bank not firing at all it would mess up the values for sure Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF