Part 2 - G40 Turbo caddy running issue...

[DKnight]

So i have made a slight bit of progress but only with diagnosing the problems.

Basically it is just overfuelling massively. I got an air fuel ration on from the emissions and it was reading 11 constantly.

To put into context, on a working g40 it read 14-15 when running correct. When unplug either blue temp / lambda it reads 13.

so the readings i am getting seem to be bypassing the signal from the sensors. Which leads me to think its a dodgy wire somewhere maybe getting a feed or not earthed right, but which would cause the ecu to ignore/not get the signal?

When you unplug the blue temp sender all the polos i own the rev range raises (when up to temperature), but on my caddy it does not, it is irregular and in some instances it coughs and splutters and runs rubbish, which at least tells me the signal is being read by the ecu, but ignored?

Its a proper head fk this issue, in all my time never seen anything like it.

Ive swapped ECU and every sensor, injectors etc nothing has not been swapped

any ideas would be great

cheers

[Andy]

What AFR does it read with a stock chip and stock injectors?

You haven't installed a pressure switch instead of the WOT switch and got it setup so the ECU always thinks it's WOT have you?

[DKnight]

afr does not change even if swapping ecu and injectors, it is currently set up completely standard with stock injectors and ecu.

Correct switch is fitted yes, tested it manually and also swapped the throttle for a standard G40 one and still same. I did at first think that this was the problem.

[Andy]

Have you had a fuel pressure gauge on the end of the fuel rail?

[DKnight]

got one permo on it 2-3 bar iirc

[Alexiskayak_7]

Sounds like a loom issue Dan.
Test the connetions and the Ω resistance of the loom.

[DKnight]

swapped the ecu loom and still exactly the same.

Its got to be something basic i am overlooking but sweet mother i can not figure it.

Taking it back to basics what can directly effect the ecu to tell it to over fuel, i know blue temp sensor and lambda but i sense something else like i say is bypassing it.

[Andy]

You need to actually follow the diagnostic guide on here, and measure the various sensor resistances at the ECU connector end of the loom with it all plugged in.

Is your knock sensor and wiring harness for it okay?

Have you got the throttle switches/knock sensor/CO pot wiring all in the correct place?

What actually is your fuel rail pressure at idle? Should be 3bar above manifold pressure, manifold will prob be about -0.5bar (i.e. vacuum) so a gauge pressure of 2.5bar would be about right.

What does the AFR do if you unplug the lambda probe or blue temp sensor on the Caddy?

What resistance is the CO pot set to?

100% sure injectors and chip are stock?

[DKnight]

yeah the measuring at the ecu end i did try but electrics and understanding is not one of my best.

Knock sensor has not been swapped but wiring appears to be fine, will check that tho

yes t/b switches co2 all correct places and checked and double checked.

i will double check the fuel pressure but i seem to recall it is 2-3bar.

afr does not alter one bit with the lambda and blue temp unplugged, this is the weird bit as if you unplug the blue temp sometimes it stutters and runs crap. New plug on the blue temp wire too and tested.

CO pot is set to the stock level, 450 or something.

injectors are defo stock and ecu too, got 3 ecu's to chose from and all labelled up