Air Flow Meter + car problems

[Steve Meade]

----------
> From: avos at cochlear.com.au
> To: diy_efi at coulomb.eng.ohio-state.edu
> Subject: Re[4]: Air Flow Meter + car problems
> Date: Tuesday, May 06, 1997 6:37 AM
> 
>      
>      Recently my car has been performing badly at low to medium revs as 
>      boost comes on. It seems to fiddle around with settings when you 
>      initally put your foot down until it decides what it is going to do
(a 
>      few seconds sometimes) and then it runs great. It is annoying under 
>      hard acceleration, as it will hesitate and then hit you with an 
>      almighty boot in the back. I am sure that this is not good for my 
>      engine, and have lowered my boost level to ensure that I will not 
>      damage anything. I have replaced the fuel filter, oil and
oil-filter, 
>      spark plugs, and cleaned the air-filter in the hope that it may be 
>      some blocked filter, or bad spark, but all this with no success. I
am 
>      starting to wonder whether a sensor is working incorrectly on my
efi. 
>      I have several other ideas before I narrow it down to the efi - fuel

>      pump (not supplying enough pressure), fuel pressure regulator (Does 
>      anyone know how to check the fuel pressure is constant under engine 
>      load on a 4WD car for which I do not have access to a 4WD dyno), 
>      fluctuating boost (though this is not apparent from my boost guage),

>      blocked injectors (though I have run petrol additive injection
cleaner 
>      with no effect on the problem). If all this fails I will no know
where 
>      to start - Does anyone have any ideas on what could cause such a 
>      problem. The weird thing for me is that it seems to run fine once it

>      has started to sought it itself out and reached high revs, which
seems 
>      to me to rule out the chances of it being a fuel delevery problem?
>      
	That's very interesting since my car ('87 BMW 325is) tends to do the very
same thing when you first start it up. If I start, back down off my
driveway (no throttle) and then push the accelerator aggressively it will
have a sudden loss of power followed by a dramatic jerk forward about 1
second later as the engine comes on full speed. If I don't give it much gas
starting off it won't do this at all and it will only do this while driving
down the first part of my street in the morning. (about 15 seconds) After
that it accelerates buttery smooth. I think your problem may be air meter
related though. If something accidently got lodged into it than it might
bind and produce the studdering effect. I would check that first.

>      Any advice will be appreciated, I am starting to my pull my hair
out. 
>      Note that my car has had no modifications done recently, and ran
fine 
>      for a year with the modifications that it has, so I doubt that it
has 
>      anything to do with any modifications that I have done.
>      
>      Adrian  
>