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Old 28th January 2020, 16:41   #21
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Just heard back from the garage, confirmed low compression on 4. The rear cylinder head has to come off for inspection, he can’t do it until Next Monday. ☹️. Cam belts were done 30k miles ago. Just my luck!

Toby.


Check the earth strap on the rear bank then...


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Old 28th January 2020, 20:27   #22
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I don’t have the equipment for a compression test.
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It's inexpensive to buy Toby.

Simon
Don't you it's about time you got off your sofa Simon, and prove yourself to the membership?, Banbury is only about sixty miles up the road from you, and I'm sure with your superior KV6 knowledge, you can soon put those spanner monkeys in their place.

I assume you own a compression tester, and even know how to use it, and more to the point, think of how you are you going to tell the mechanics that they are making a big mistake by misdiagnosing HGF or a burnt out valve, or a hole in a piston, when in fact it's the Herby clips in the wrong place, coupled with non adherence to the MGR coolant refill procedure, or perhaps as the belts that were replaced 30,000 miles ago, it's the possibility of a non functioning low speed fan, due to none ECP brushes having been used in a previous repair

Anyway back from Simon's fantasies about being better than everyone else at repairing the KV6 Toby, for what it's worth, I suspect there may been an earth left off the rear bank, and there is a defective coil driver transistor in the ECM as a result, this can be diagnosed by unplugging the ECM and sniffing the connector, as if my hunch is correct, there will be a very distinctive burnt electrical smell.

As to low compression, I've seen these run with compression as low as 100 PSI without a significant misfire, and down as low as 85 PSI with a splashy intermittent misfire.........is the symptom a constant misfire on No.4, as in running on only 5 cylinders?

Please let us know how you get on, Simon is waiting to tell everyone "I told you so"

Brian
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Old 29th January 2020, 07:58   #23
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Thanks for that info Brian & Simon. Yes, it is a constant misfire, I.e only firing on 5 cylinders, with no. 4 being the culprit. I am going to pop down to the garage in Banbury and check the Earth strap and ECU before they start expensively ripping apart the engine. Is the earth strap obvious? Where does it attach? As the garage can’t start work until next Monday I have time.

Cheers


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Old 29th January 2020, 10:20   #24
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Thanks for that info Brian & Simon. Yes, it is a constant misfire, I.e only firing on 5 cylinders, with no. 4 being the culprit. I am going to pop down to the garage in Banbury and check the Earth strap and ECU before they start expensively ripping apart the engine. Is the earth strap obvious? Where does it attach? As the garage can’t start work until next Monday I have time.

Cheers


Toby
As I said Toby, remove the plug from the ECM and take a sniff at the connector, if it is a MOSFET failure, it will stink to high heaven, this can be further confirmed by dismantling the ECM, as the device is in a SMD version of a TO220 package, ie a large 10mm square transistor on a heatsink in close proximity to five others, and it will be obvious if this has failed.

Sadly I don't have a picture of a KV6 earth strap to the rear bank, but this would be something one of the V6 boys could sort out

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Old 29th January 2020, 10:35   #25
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The earth strap is a small black wire with a ring connector on the end, have a look behind the rear bank of cylinders towards the bulkhead, it will be obvious where it exits the main engine loom.


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Old 29th January 2020, 10:44   #26
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Although this is the front bank this is what you’re looking for on the rear.

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Old 29th January 2020, 10:45   #27
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Have a look at this thread: https://the75andztclub.co.uk/forum/s...d.php?t=225611 post 8 - there's a picture of the earth on the rear bank.

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Old 29th January 2020, 19:12   #28
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So then, anyone want to suggest opening up the EMS 2000 to see it there is a fried MOSFET on the board?

Brian
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Check the earth strap on the rear bank then...


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I’m gonna check both these as I also have a C4 constant misfire with codes P0304 and P1319. I checked the O2 sensors and both front and rear bank ones pulse okay and the third one doesn’t pulse at all but shows a small current, from what I’ve read it’s doing what it’s supposed to do.

I’m interested about this earth strap, I’m gonna check that as the car had a replacement thermostat, spark plugs and IMGs.
If the ECU smells of electrical burny burny, what’s the solution Brian?
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Old 29th January 2020, 20:22   #29
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I’m gonna check both these as I also have a C4 constant misfire with codes P0304 and P1319. I checked the O2 sensors and both front and rear bank ones pulse okay and the third one doesn’t pulse at all but shows a small current, from what I’ve read it’s doing what it’s supposed to do.

I’m interested about this earth strap, I’m gonna check that as the car had a replacement thermostat, spark plugs and IMGs.
If the ECU smells of electrical burny burny, what’s the solution Brian?
It's a service exchange ECM Al, I've never been able to successfully replace these transistors, as the "PCB" is actually a mylar about .0015" thick folded in half, and the heat involved removing a great hulking transistor from a previously damaged board, normally kills it

I can transfer the data to another unit to make a plug a play replacement though

Brian
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Old 29th January 2020, 20:31   #30
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It's a service exchange ECM Al, I've never been able to successfully replace these transistors, as the "PCB" is actually a mylar about .0015" thick folded in half, and the heat involved removing a great hulking transistor from a previously damaged board, normally kills it

I can transfer the data to another unit to make a plug a play replacement though

Brian
The earth strap is secured to the rear bank and the wiring looks okay. I’ve yet to run a wet and dry compression test so is it still more common to have a fried transistor than failed piston rings?
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