[Mk2] [Turbo] Motec or Fuel problem?

[Jimbob]

Ok,

My car started playing up a bit some time back missfiring. I knew one injector had previously stuck open. I could move that injector round and the mis followed the cylinder it was in. I put in new injectors with same part number (Seimens 872cc / 85lb/hr). The missfire seemed to go, but I thought the car felt like it was a little rich, occasionally missed in first and on heavy boost. The miss got a bit more regular and the car idled a bit crap. Tried all the obvious ignition things to no avail, so I got the old injectors serviced
(knowing the flowed right for the map) and got them re-fitted. The car was still missing.

So I have played with an old dizzy cap (copper contacts) and cleaned the almost new one which was fitted, fitted a new rotor arm and have fitted a new ignition coil. I tried taking off the leads and swapping with spares and even resistance checked them and they seem fine. I have ordered a new set anyway.

Tonight whilst still trying I noticed the car seemed really rich and the exhaust was a bit white, misfire worsening. I checked in the exhaust pipe and some fuel had pooled in it! I swapped back again to the new injectors to try them, having lost confidence in the cleaned/serviced ones. The car is still heavily missfiring.

Whilst messing about, pulling off the no. 2 and 3 leads has least affect on idle whereas 1 and 4 causes the car to almost cut out. Now the miss on idle is bad enough to make it struggle to keep running and its running stupid rich. Pulling off any lead causes problems.

I'm scratching my head as even if I lost a spark to two cylinders I cannot imagine this much fuel getting through? I wondered if my injector loom has developed a short (maybe got hot).

So anyone got ANY idea.

MY next option is probably to try fault finding on the injector harness, or to find out if the Motec does a simple check of whats connected? I'm think about doing a resistance check of the loop with each injector on and from the same loop to ground?

HELP!

[ashley]

Probably a really dumb question, but are you sure it was fuel in your exhaust?

Probably wrong, but white in the exhaust gas could be steam, not firing properly on 2 & 3....could be head gasket gone, and water coming into the cylinders? Just an idea...

[Jimbob]

Should have said, water level is good and holding. Definately fuel, i sloshed my hand in it and smelt it. Its a 5" exhaust so easy to get to

[ashley]

Fair play- was a long shot, sometimes we overlook the easy things!



....and 5 inch

[Jimbob]

I know 5" is a little plump, its a 3" system. I'm struggling as if its on the Motec side I havent a clue, trailer time!

[Mike N]

Jim,

I would look at the following for fuel issues,

fuel pump running at max all the time?
adjustable fuel pressure regulator adjustment?
air filter / intake system (blockage or air leak) (I/C internals)?
water temp sensor failure (overfueling)?
cold start system air leaks (compensating with extra fuel)?
Injector O ring failure (allowing fuel thru)?


Are the cyl comp's equal?
Cyl leak down test?
CO check (cold and hot)?

Plug grade.


Bit of a pain but convert back to a std ecu, inj, fuel pump set up and see if the engine is the same as it is now etc.


Mike

[Jimbob]

Going back to stock ECU is not really an option with all the wiring that's been removed and the nods to the car.

It's too much fuel as opposed to not enough, and a lot too much. Coolant sensor wouldn't affect it this much.

Really looking for obscure gems or motec help.

[Driftlimits Performance]

compression test results?

[Jimbob]

Did a compression test, each cylinder at ~12bar almost identical so that rules that out.

[ashley]

You have checked the plugs are sparking & checked the gaps haven't you?

[Jimbob]

Pretty confident on it, got new leads hopefully be here tomorrow, i'll drop some lower grade plugs in too, got 8's in so will pop in some new 6's. The plugs were all black and sooty.

[ashley]

Yep- does sound like it's time to plug into the ECU to see what's what!

[Jimbob]

I'll be upset if its the ECU as its done no more than 1000 miles.