15 replies to this topic

[Shifty]

Bit of history first..

 

On the way back from the IMM my Mpi overheated (Badly)  and blew the head gasket.  I've only just got around to doing, mainly as I'd pulled the head and didn't want to leave it exposed all winter.

 

Had the head checked skimmed(plus new stat and water pump) and went to start it and it was missing like a pig. Plus you'd blip the throttle and the revs would stay up.

 

After investigation I found it was only firing on 1 and 4, tried all the usual stuff and couldn't get any life from 2 and 3.  Decided the coil could be knacked so bought a new one and fitted it, still no good and exactly the same.

 

I've had it on my acr and cleared all the codes, ran it and the codes didn't come back.

 

I'm leaning towards an ecu fault and am tempted to get it sent away for repair.  

 

Any other thoughts before I do?

[Midas Mk1]

Air leak around the inlet? I had the exact same symptoms including misfire when I swapped a complete MPi inlet over, assuming the leads are on the correct order too? :)

[Shifty]

I'm not actually getting any spark from the coil on 2 and 3 , the high revs could be from an inlet leak though.

[sledgehammer]

I would check the wires that trigger the coil pack & the connectors - ecu & coil

 

try the cheap stuff first

 

not sure , but one wire triggers 2&3 - and another triggers 1&4 ???

 

I'm sure the MPI's are wasted spark coil ?

 

wonder if coil problem could weaken head gasket thru detonation ?

 

Or maybe barking up the wrong tree (getting old & tend to bark at anything)

Edited by sledgehammer, 12 December 2014 - 10:34 PM.

[FlyingScot]

Yes wasted spark ignition on MPi
Check wiring from coil pack to ECU for breaks. Can you change leads at coil end and get the spark to move to 1&4?
Clamp hose on IAC to see if revs drop (could be ECU is operating the IAC)
Unless your replacement coil unit is duff sounds like one of the coil driving circuits in the ECU is shot.
Check the resistance of the coil pack (low voltage and high voltage sides).
I think Rob Mac published this before in a document he made but I couldn't lay my hands on it

FS

Edited by FlyingScot, 12 December 2014 - 11:06 PM.

[mini 4o]

HI have a look at the coil plug C197 check the two wires that trigger the coil.. WS white/slate and WB white/black . good little test if you have no meter is to see if one has no single is to reverse the wires . do this with all 4 spark plugs removed. .And yes it is a lost spark system.

[Ethel]

Can't say with 100% certainty, but it most likely has a common supply to the coil and each side is alternately earthed by the ecu. Just as with points, it's breaking the circuit that makes it spark. So, it can fail with the circuit either permenantly open or closed.


A blind guess, that even I don't think likely, could it be the cam sensor - or connected to the injector? It'd be chucking unburnt fuel intro the exhaust if it was just the igntion.

[Shifty]

Did some more checking today and the wiring to the coil from the ecu is fine, it's looking more and more like the ecu at fault.

[Fast Ivan]

are you certain that the replacement coil is ok? the ecu's are very robust bits if kit, not saying they are bullet proof but certainly more reliable than the rest of the mpi setup (looms, earths, coil etc. etc....)

certainly worth checking the coils resistance before you condemn

[Shifty]

That's a good point to be honest and one I didn't consider.  

 

Any idea what the resistance should be?

[Fast Ivan]

at 20 degrees primary resistance 0.41 to 0.61 ohm, secondary resistance 6200 to 6700 ohm 

[FlyingScot]

You had made a document on this Rob (I mentioned above) can you post it?

FS

[Shifty]

I've sent the ecu off for testing and it does indeed have an ignition fault.

It's being repaired by ATP in Cannock and I should have it back next week.

It looks a faulty coil took it out.

More expense but never mind.......

[sledgehammer]

at least you now know

 

& it gets a car back on he road

[FlyingScot]

Bad luck Shifty the MEMS is tough but not indestructible. At least you have it solved.

FS