Quaz

I am begining to believe this is almost normal Euro S2 operation as my car does the same thing. When you go full throttle there is like a slight hesitation then hang on. At part throttle it feels like it is running on 7 or 6 cylinders. I think part of the problem may be the gas around here. When the car was originally designed it was only supposed to run on 95 octane non-reformulated. Now the best I can put in it is 93 octane reformulated. When it is cool outside the air temp keeps the intake cooler thereby raising the octane by reducing knock. As the octane rating is just the resistance to knock. Anyway, I am going to try running octane boost this summer and see if it helps the problem on the hotter days. I suspect it might.

John Speake

Hi Thomas, Seeting the idle mixture a bit richer won't help the hesitation when you open the throtle, I'm afraid.........

Quaz: The Euro S2 seems to have bben mapped a bit on the "weak" side, as far as fuelling is concerned. Any slight problem, like injectors down on flow, or (commonly) the MAF ageing, and it will hesitate under acceleration and be low on power. It is easy to tell if the MAF is the cause if the car pulls hard at WOT, but is poor at smaller throttle openings.

When the weather is hot, the ECU tends to weaken the mixture, making the symptoms that bit worse, as you have observed.

WallyP

93 (R+M)/2 is better than 95 RON.

drnick

an ageing MAF?!

i mean everything does age as a function of time which is inevitable, but how significant is this with the MAF?

for myself now fuelling problems have fallen down the list a bit following a broken windscreen and split fuel pipe!

_Thomas_

Hi

my '81 BMW 635 which has a AFM with a flap (which operates a potentiometer for the signal which goes to the comp) was clearly running lean at some time - there I could just set the poti a couple of teeth richer and the problem was solved - so from what I understand now this hot-wire MAF cannot be adjusted and there is no way around replacing the Pt wire as John suggests ...

Also now I have some statistics about fuel consumption, driving it quite hard (mix city, motorway, highway) I used just 13 liters/100 km of gasoline (super unleaded 98 with no lead substitutes, should I use some??) which is certainly not indicative of over-rich running.

I repaired the leak in the air pump diverter valve vacuum actuator (previously hose was blocked to stop vacuum leak), but now that valve is working it doesn't seem to make a lot of difference ...

Cheers Thomas

_Thomas_

Hi all

just to let you know that I bought a refurbished MAF from John Speake and it has really resolved my problem at last, the car runs perfectly now.

Many thanks to all who contributed to this thread which from my side can now be concluded
Cheers Thomas

Quaz

Thomas, thanks for the update. Now I just have to put this resolution in my memory banks for when mine gets a little worse.

ootoddo

Hi all
hope i can get some help here. I have an 84 928s. was running fine one day, it sat for a month and now it idles just ok, runs only fair to half throttle then kinda nose dives and gets real rough after that. one thing i have noticed is what sounds like an air leak at the rear passenger side of the motor. any ideas? Thanks