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Author Topic: 2.5 petrol manual estate misfiring  (Read 10361 times)

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Tick Tock

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Re: 2.5 petrol manual estate misfiring
« Reply #60 on: 13 August 2018, 19:08:14 »

Strangely enough, I was servicing the car and cleaning the breather system, when I came across the PCV.... not knowing what it was, I asked the question on here with a picture of the solenoid valve. I've since read up on the EVAP system and have a better understanding of what it does and how it works.

After mentioning the fact it was open all the time and not responding to 12v on the bench (it doesn't matter which way you connect it, it's just a coil), I was advised to forget about it and quote "If the car runs fine, if it ain't broken don't fix it. :y"

Not wanting to go too much off topic with regard to your misfire problems, I've since been told it does matter, and it could cause the petrol tank to collapse (in extreme conditions) if the engine is drawing in fuel vapour from the purge system when the valve is constantly open. It's just passed its MOT test and has been running very well with no fault lights. It's possible the line from the tank to the canister is blocked, but nobody knows for sure.

I don't know if the PCV and associated pipework is causing your problem, but at the very least you need to make sure the breather system / plenum isn't drawing in air from the engine bay, i.e. make sure it's connected (or blanked off) before going to the next step of your fault diagnosis.
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terry paget

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Re: 2.5 petrol manual estate misfiring
« Reply #61 on: 13 August 2018, 20:02:36 »

Strangely enough, I was servicing the car and cleaning the breather system, when I came across the PCV.... not knowing what it was, I asked the question on here with a picture of the solenoid valve. I've since read up on the EVAP system and have a better understanding of what it does and how it works.

After mentioning the fact it was open all the time and not responding to 12v on the bench (it doesn't matter which way you connect it, it's just a coil), I was advised to forget about it and quote "If the car runs fine, if it ain't broken don't fix it. :y"

Not wanting to go too much off topic with regard to your misfire problems, I've since been told it does matter, and it could cause the petrol tank to collapse (in extreme conditions) if the engine is drawing in fuel vapour from the purge system when the valve is constantly open. It's just passed its MOT test and has been running very well with no fault lights. It's possible the line from the tank to the canister is blocked, but nobody knows for sure.

I don't know if the PCV and associated pipework is causing your problem, but at the very least you need to make sure the breather system / plenum isn't drawing in air from the engine bay, i.e. make sure it's connected (or blanked off) before going to the next step of your fault diagnosis.
Thanks for that explanation. Of course you are right, it doesn't matter which way yu connect it, it's only a coil. I now wonder how air gets into the tank to allow fuel to depart without reducing the pressure in the tank. Can it be via the purge line?
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TheBoy

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Re: 2.5 petrol manual estate misfiring
« Reply #62 on: 13 August 2018, 20:55:39 »

Is the code 19 still present?
On the earlier V6 if you read the codes with the ignition on but engine off then it will always report code 19. It should clear when the engine is running. Else the sensor is foobar or the connector still has an issue.
Cobblers ;)

A 19 is always a corrupted signal. And is 99.9% of the time the sensor, with that 0.1% being a faulty flywheel or ECU.

With engine not running, you get a 30 (No RPM signal) on a pre 2001 V6
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terry paget

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Re: 2.5 petrol manual estate misfiring
« Reply #63 on: 13 August 2018, 22:26:22 »

Where is the purge valve on a 2.2? Haynes says on the 2.0 it is mounted on the rear of the cylinde head, on the RHS of the DIS module. The 2.2 has no DIS module, I imagine the purge valve is in a similar place at the back of the head, but cannot see it in any of my photos. Haynes says access may be gained from above or beneath. I enquire because I have an MOT failed 2.2 here I am stripping for spares.
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Doctor Gollum

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Re: 2.5 petrol manual estate misfiring
« Reply #64 on: 14 August 2018, 00:41:58 »

I believe it attaches to the head slightly below the coolant 'bridge'...

I would check, but no longer have one to explore. Best bet is to follow the plumbing from the inner wing to the engine, it runs alongside the fuel lines iirc ;)
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terry paget

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Re: 2.5 petrol manual estate misfiring
« Reply #65 on: 14 August 2018, 20:15:11 »

Today I changed the radiator. I thought the engine might be overheating. This produced no change. I give up.
I will drive this car around, and ponder what is going on. It's not a bad misfire, it only occurs occasionally, when pulling full throttle at low rpm.
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Andy H

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Re: 2.5 petrol manual estate misfiring
« Reply #66 on: 14 August 2018, 22:32:50 »

Today I changed the radiator. I thought the engine might be overheating. This produced no change. I give up.
I will drive this car around, and ponder what is going on. It's not a bad misfire, it only occurs occasionally, when pulling full throttle at low rpm.
Did you check/change the spark plugs?

The erosion of the outer electrodes causes the spark gap to increase quite dramatically as the plugs age.

I will post a photo when I get my web hosting working again.....
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terry paget

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Re: 2.5 petrol manual estate misfiring
« Reply #67 on: 15 August 2018, 08:29:36 »

Today I changed the radiator. I thought the engine might be overheating. This produced no change. I give up.
I will drive this car around, and ponder what is going on. It's not a bad misfire, it only occurs occasionally, when pulling full throttle at low rpm.
Did you check/change the spark plugs?

The erosion of the outer electrodes causes the spark gap to increase quite dramatically as the plugs age.

I will post a photo when I get my web hosting working again.....
Yes. I have changed spark plugs, plug leads, DIS pack, cam cover gaskets, radiator. The engine runs all right, but not as sweetly as my other 2.5 petrol in regard to full throttle low rpm running. It has been 'chipped' by a previous owner, now I wonder if this could be relevant.
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Doctor Gollum

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Re: 2.5 petrol manual estate misfiring
« Reply #68 on: 15 August 2018, 08:39:17 »

Could well be. Now that you mention it...  ::)

I do worry sometimes...
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terry paget

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Re: 2.5 petrol manual estate misfiring
« Reply #69 on: 15 August 2018, 15:34:16 »

Could well be. Now that you mention it...  ::)

I do worry sometimes...
I believe previous owner, OOFer ajsphead, chipped it to better match engine to used diesel diff, fitted to replace worn original. That diff became very noisy last year and I replaced it with diff I salvaged from scrapped 3.0. That diff now displays worn crown wheel and pinion, much clonking, and will soon be replaced by diff off son's MOT failed 2.2. I hope the chip can keep up with all these diff changes.
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Doctor Gollum

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Re: 2.5 petrol manual estate misfiring
« Reply #70 on: 15 August 2018, 16:07:58 »

It's a bit like saying 'my lawn doesn't go stripey when I mow it'. You'll be offered101 suggestions as each one doesn't quite work. Then finally, you mention that you use a goat instead of a roller mower, and, by the way a whole family of moles live under it.

If you believe that the chip is the root of your issues, fit a stock ecu and report back... ;)
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terry paget

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Re: 2.5 petrol manual estate misfiring
« Reply #71 on: 15 August 2018, 17:25:59 »

It's a bit like saying 'my lawn doesn't go stripey when I mow it'. You'll be offered101 suggestions as each one doesn't quite work. Then finally, you mention that you use a goat instead of a roller mower, and, by the way a whole family of moles live under it.

If you believe that the chip is the root of your issues, fit a stock ecu and report back... ;)
Thanks Doc, I love your simile. I thought that Senator ECUs were interchangeable, but Omega ECUs were not, as they contain customised information like ignition and alarm codes.
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Re: 2.5 petrol manual estate misfiring
« Reply #72 on: 15 August 2018, 18:37:17 »

It's a bit like saying 'my lawn doesn't go stripey when I mow it'. You'll be offered101 suggestions as each one doesn't quite work. Then finally, you mention that you use a goat instead of a roller mower, and, by the way a whole family of moles live under it.

If you believe that the chip is the root of your issues, fit a stock ecu and report back... ;)
Thanks Doc, I love your simile. I thought that Senator ECUs were interchangeable, but Omega ECUs were not, as they contain customised information like ignition and alarm codes.
Post 96 ones are paired to the immobiliser
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Re: 2.5 petrol manual estate misfiring
« Reply #73 on: 15 August 2018, 20:11:45 »

Is the code 19 still present?
On the earlier V6 if you read the codes with the ignition on but engine off then it will always report code 19. It should clear when the engine is running. Else the sensor is foobar or the connector still has an issue.
Cobblers ;)

A 19 is always a corrupted signal. And is 99.9% of the time the sensor, with that 0.1% being a faulty flywheel or ECU.

With engine not running, you get a 30 (No RPM signal) on a pre 2001 V6
Hmmm 30? Did you mean 31?

Apologies. Looks like I had that the wrong way round. I must have been thinking of 31 = no RPM signal as opposed to 19 = incorrect RPM signal. Anyway it isn't confirmed whether code 19 is still a problem, since the sensor connector was fixed. So it might all be irrelevant.

Concerning the misfire, not all failed coil packs have splits or cracks or melted bits. I have an original here, somewhere, that looks fine but misfires under load.

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terry paget

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Re: 2.5 petrol manual estate misfiring
« Reply #74 on: 16 August 2018, 08:25:32 »

Is the code 19 still present?
On the earlier V6 if you read the codes with the ignition on but engine off then it will always report code 19. It should clear when the engine is running. Else the sensor is foobar or the connector still has an issue.
Cobblers ;)

A 19 is always a corrupted signal. And is 99.9% of the time the sensor, with that 0.1% being a faulty flywheel or ECU.

With engine not running, you get a 30 (No RPM signal) on a pre 2001 V6
Hmmm 30? Did you mean 31?

Apologies. Looks like I had that the wrong way round. I must have been thinking of 31 = no RPM signal as opposed to 19 = incorrect RPM signal. Anyway it isn't confirmed whether code 19 is still a problem, since the sensor connector was fixed. So it might all be irrelevant.

Concerning the misfire, not all failed coil packs have splits or cracks or melted bits. I have an original here, somewhere, that looks fine but misfires under load.
That's worrying. The DIS pack I removed looked all right, as did its replacement. No change in fault.
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