Phase 3.5+ boost cut problems

[jtimkey]

I am getting boost cut at various levels power wheel at full throttle.
i have installed new pump 909 and filter..voltage at pump undercrank is over 12.5v.
i have had injectors cleaned but still it cuts. i assume this is the lambda board cutting it because its lean..???
what can i try next..i do not want to remove lamba function as this stops me melting a piston..
any other ideas...
can i test fuel pressure when at standstill but reving car ?
cant think what else to check ?
it has had new lambda a year ago..
thanks
john

 

[ASH]

Hi John !

Please check if your fuel pressure is constant when the lambda is cutoff !

When your fuel pressure is 4.5 bar + boost pressure , then its another reason !

Please check the voltage diffrence between PIN 24 inside the motronik and the connection of the intake manifold !

When you measure a voltage MORE than 0.15V DC then put an additional GROUND wire from PIN24 inside the ECU to the intake manifold like 1.5mm² in brown , that everybody see thats a ground wire !

The best way is to install a 1 pin connector outside the ECU , then you can take it out very easy !

In these cases the motronik is reading the wrong lambda voltage , the lambda sensor is fully ok with its signal , but the motronik is reading like 0.15 to 0.25 V less and the lambda cutoff is getting active !

In the last weeks we had this problem very often , the motronik engine harness has some connection points where many wires were taken together , also the main ground connection inside the engine harness is getting worse in the lifetime of the engine !

regards ASH

 

[jtimkey]

Ash,
if i understand you correctly i need to start the car and measure voltage at pin 24 at idle. If this is more than 0.15v dc then run a new wire direct from pin 24 to the place of termination ?
were does pin 24 go to on the inlet manifold ?
thanks for you help ash
rgds
john

 

[ASH]

Hi !

Again : Pin 24 connects ECU-GND and Intake manifold at the skrews for the injector row !

Thats your mistake , im sure !

regards ASH

 

[jtimkey]

sorry ash yes i understand the earths that are on the injector rail run back to pin 24 on the ecu.
thanks i will check this evening..
rgds
john

 

[jtimkey]

ash. i found the problem..
it was the lambda sensor, it was a non-bosch item..
i have replaced with a bosch item and all works fine.
thanks for you help.
cheers
john

 

[Not_Too_Fast!]

Isnt it nice when a plan comes together!!

 

[jtimkey]

It is indeed..
very quick now...apart from clutch slip on position 4 and 5..

 

[Russ]

I have suffered lambda cut on my car for a quite a while, despite the fact that I pretty much knew that the mixture was ok.
So I tried this pin24 mod and rewired the ecu to enable lambda cut again - and it works fine now

One thing I did notice, and I know voltages have been mentioned before; that if you really load the electrical circuit - both heated seats, headlights, rear demister - the voltage drop makes the mixture weaken, I assume because the pump doesn't do so well :shock:
I do have an uprated pump on the car too.