S1 V6 auto back on the road at last!! - Problem solved!!

[Dean]

Matthew, get a pressure guage on the fuel rail to start with and disconnect the fuel supply and get the pump to run fuel into a jerry can to prove ample pressure and flow, check injectors next, resistance is about 1.4ohm from memory.

Easiest way would be to lift the manifold and put it in a big plastic box on top of the engine, disable the ignition and get a helper to crank while you watch the injectors fire, with an issue of this magnitute you just want to check that all injectors are actually firing an even jet of fuel, each bank of injectors is on a different section of loom and i would think if one bank of injectors is down you would have a slightly lumpy idle but it would rev with no load though as 3 pots would be dead weight and 3 would be ok, your issue seems to be all cylinders are leaning right out so stuff all fuel is getting to any cylinder.....................fuel filter, pump, fuel lines, pressure reg or a problem with electronic fuel metering.

Bit odd an engine leaning out this bad doesnt giv an EML light on, its rather bad for the engine to be leaning out like this (under load) and the ECU should see the lean burn via the O2 sensor and correct, if it cannot correct it should bring that light straight on.

D

[sdelasal]

Good progress - I agree with suggestion above, Rail pressure check would be my next step - but keep it simple first of all & leave evertyhing in place as normal from the tank/pump/filter/lines. If that is not to spec, then start substituting as Dean suggests. If rail pressure is good, then i think it points to the ecu deliberately cutting injectors. You now know though that crank position sensing and ignition system is good as the ecu is managing to get ignition timing right when you manually add more fuel.

[MTXM]

Many thanks Dean and Steve and just to report that I drove the car about a mile and it barely made the last leg with so much misfiring and spluttering!! My gut feeling is that the pump is fine as it sounds healthy enough and also the fuel pipework and injectors since you can feel the 'pulsing' in the rubber pipes against the rails. I have also disconnected the feed pipe and from the explosive discharge there seems to be good pressure, while the injectors have been changed with no effect. As the engine ran fine before removal and stood a relatively short time I think there is a much greater likelihood of a faulty wiring issue, given the various disconnections and general upheaval involved, it is just a question of where! Any further suggestions/leads would be most welcome. With regards, Matthew T.

[Dean]

Feeling a pulse in the pipe is not ideal as the damper is there to stop that and it can cause fueling issues but if your certain there is 3 bar of pressure on the rail and ample flow then you are going to be looking at a MAP problem, split or disconnected hose to sensor, duff sensor or wiring to sensor.

Throttle position sensor, wiring or sensor.

O2 sensor but I think this will have no bearing under WOT, only at cruise does the ecu use the O2 sensor to regulate mixture.

inlet air temp and coolant temp sensors could be faulty but I wouldn't have thought they could influence fueling to the point the engine would not run under no load.

The way it behaves I would think the ECU isn't seeing air flow or engine speed, I bet with idle mixture you could rev it up to 2k before it leaned out so much it wouldn't run? I would look at the above items carefully next, try unplugging each in turn as if the ecu cant see the sensor it may use a generic value based on other inputs to give you a 'get home' fuel map.

D

[MTXM]

Many thanks for your further helpful thoughts Dean and in response:

- The 'pulsing' in the fuel pipes is only slight and quite normal I think from my experience of other 12v V6 engines and I believe the pressure and flow are adequate.
- I have checked and replaced the MAP sensor and wiring and pipe and throttle position sensor and wiring but I will look again.
- The oxygen sensor has been replaced and the heater and sensor circuits are certainly working as the tip warms up and engine light comes on when unplugged.
- I have also replaced the inlet air and coolant temp sensors and again engine light and fault codes appears when unplugged.
- The engine speed must be reading presumably as there is no start with the crankshaft sensor removed.

I shall let you know how matters progress!

With regards,

Matthew T.

[MTXM]

Here is my report on the latest checks:

- unplugged MAP sensor, engine light on and initially started but would not run and fault code read.
- removed and checked MAP sensor pipe, all okay.
- unplugged throttle position sensor, running slightly rougher and fault code read.
- unplugged oxygen sensor, engine light on, running unchanged and fault code read.
- unplugged manifold air temp sensor, running unchanged and fault code read.
- unplugged coolant temp sensor, engine light on, running unchanged and fault code read.
- unplugged crankshaft position sensor, no start as before.

The above tests suggest to me that all sensors and wiring are present and correct.

Other thoughts I have had are contaminated fuel, which could explain why 'fresh' fuel direct into the inlet manifold allows revving, but I may be clutching at straws! I have added a full tank of petrol since returning to the road with a dose of cleaner additive.

I can also confirm that the 'pulsing' on the fuel rail pipes is only noticeable at idle and I am not quite sure where to go to from here!

With regards,

Matthew T.

[Dean]

Lexia time i think.

D

[MTXM]

What else will the Lexia be able to tell me Dean do you think and would it highlight contaminated fuel? Regards, Matthew T.

[White Exec]

After your successful dose of a cupful of petrol, can you safely rig up a temporary fresh fuel supply to the engine, and see what happens? I do remember trying to start a Rover V8 that had stood with half a tank of petrol for a couple of years: it was really difficult to start (expected), but also reluctant to rev, and with not a lot of available power, despite firing on all eight.

[MTXM]

I am not totally convinced about my contaminated petrol idea Chris, since the car was running rough before and after the latest refill and then more recently got very much worse! My next move will be to install a known good pump as this is not too big a task and see what happens. With regards, Matthew T.