Mi16 Severe Misfire

[matthewm 1]

My 1.9 alloy block Mi developed a problem on its first event last week. After going through a deep ford then stopping at the control 50yds later, the car idled fine although wouldn't rev up, 20 odd secs later it suddenly burst back in to life and was fine for the next 40 odd mile, then developed a misfire which very quickly got to the point where as the revs increased it would splutter violently and blow flames out of the exhaust.

 

Pretty sure its an ignition fault due to the unburnt fuel and the fact the rev counter goes a bit crazy - car is running the Motronic 1.3 that came on the 405, have changed the ignition amp for 2 others, the ignition coil, the water temp sensor and the CPS. Was put together with a newly made loom which hasn't chaffed away anywhere, and all the connections on the new pins fitted seem fine, so I'm not suspecting a wiring fault just yet.

 

Also the car struggles to turn over with the ignition on - starter will turn engine over fine with it off - but it occasionally stalls the starter motor it when its on.

 

Kindly huw 'large' has sourced me a 3-row ECU to try - is there anything else that anyone can think of, together with a bit of reasoning.

 

Thanks a lot!

[welshpug 1,666]

quite possible that there is water sitting on top of the plugs, though if the rev counter is playing silly buggers it might be the ignition amp or coil, or the live supply to them from the relays.

[matthewm 1]

Have taken cover off and checked all dry on top, including inside the distributor cap which is brand new - supply to the coil and amp has been changed to a direct feed (via fuse) and has full voltage.

Edited June 10, 2010 by matthewm

[C_W 3 1 Cars]

Could be one of the ignition relays (brown/green?), usually on the inner wing if the 405 loom was used. This is usually a complete engine cut out rather than a general misfire though.

 

There's also the ingition amp sat quite low on the pass side. Also the rotor arm which caused my misfire a few years ago despite looking new.

[matthewm 1]

Could be one of the ignition relays (brown/green?), usually on the inner wing if the 405 loom was used. This is usually a complete engine cut out rather than a general misfire though.

 

There's also the ingition amp sat quite low on the pass side. Also the rotor arm which caused my misfire a few years ago despite looking new.

As mentioned above the coil has a direct feed, when you say ignition relays do you mean injection relays, as one controls the fuel pump, and the other operates the injectors. As per first post, have tried 3 different ignition amps with no joy.

[SweetBadger 94]

Another thing to check is the air flow meter - make sure it is still well sealed and water hasn't got into the wiper/arm circuit board.

 

I had exactly the same symptoms after driving in some very wet weather and crossing a flooded bit of road a few years back; water got in, corroded the afm circuit board and the car was soon almost undrivable but ok on idle.

 

Edit - just reread original post about the rev counter jumping, in which case it is more likely to be ignition related, still probably worth checking the afm is ok anyway.

Edited June 10, 2010 by SweetBadger

[welshpug 1,666]

don't forget those relays also power up the ecu, no ecu power = no spark.

[matthewm 1]

don't forget those relays also power up the ecu, no ecu power = no spark.

 

Have moved these relays so they are internally mounted and are both new, and put the ECU on its own fused supply.

Am I correct in thinking providing my ignition amp and coil are o.k (which have both been proved) the problem is the ECU not giving the correct signal via the light green wire going to the amp.

So either the ECU has gone bonkers, or whatever is giving it its signal to switch the amp is at fault.

Is it just the signal from the Crank Position Sensor that tells the ECU when to tell the coil to fire - or is it controlled by something else I'm missing?

If anyone can make sense of that!