Strange problem in my S4
10-23-2007, 10:29 AM
#1
Racer
Thread Starter
Strange problem in my S4
I put my 1987 S4 manual (Euro) through it's MOT test last week.
A previous mechanic had turned the mixture richness pot all the way up to
the maximum so it failed on emissions (9% CO at idle with no air pump).
However 15 minutes with a screwdriver and it was putting out 2.85% CO which
is well within a test pass, but well above the 1% CO that John Speake measured when fitting my recent new MAF.
Turning the mixture richness down also seemed to cure the lumpy idle as
well. Drove the car through rush hour traffic to Epsom over the weekend and
she was behaving very well. Noticed that it still has a slight
misfire/hesitation in the upper rev range when nailing it.
However, on the way back from Epsom, problem- I came off the A3 and down a
slip road to some traffic lights. As I took my foot off the gas and put the
clutch in to change to 1st, the whole dash lit up. Basically the car had
stalled. Restarted straight away, but something not right - car
running rough and showing funny characteristics.
It was bunnyhopping at 30mph in third gear. Simply impossible to make any
kind of reasonable progress in traffic without a horrible heel and toe'ing
to stop it stalling. The only way to make any kind of progress was to hold
it in a lower gear. It used to do this when the mixture was too rich but
given that it's now been turned down as low as it will go I am at a loss.
Could it now be too weak?
Joel
PS: It has new leads, new rotor arms and caps, and a new (second hand)
ignition control amp off a late S2. I'd be interested to hear if any of
these could be at fault.
A previous mechanic had turned the mixture richness pot all the way up to
the maximum so it failed on emissions (9% CO at idle with no air pump).
However 15 minutes with a screwdriver and it was putting out 2.85% CO which
is well within a test pass, but well above the 1% CO that John Speake measured when fitting my recent new MAF.
Turning the mixture richness down also seemed to cure the lumpy idle as
well. Drove the car through rush hour traffic to Epsom over the weekend and
she was behaving very well. Noticed that it still has a slight
misfire/hesitation in the upper rev range when nailing it.
However, on the way back from Epsom, problem- I came off the A3 and down a
slip road to some traffic lights. As I took my foot off the gas and put the
clutch in to change to 1st, the whole dash lit up. Basically the car had
stalled. Restarted straight away, but something not right - car
running rough and showing funny characteristics.
It was bunnyhopping at 30mph in third gear. Simply impossible to make any
kind of reasonable progress in traffic without a horrible heel and toe'ing
to stop it stalling. The only way to make any kind of progress was to hold
it in a lower gear. It used to do this when the mixture was too rich but
given that it's now been turned down as low as it will go I am at a loss.
Could it now be too weak?
Joel
PS: It has new leads, new rotor arms and caps, and a new (second hand)
ignition control amp off a late S2. I'd be interested to hear if any of
these could be at fault.
10-24-2007, 05:49 AM
#3
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Join Date: Mar 2005
Location: Kent (UK)
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The bunny hopping for me was caused by a bad MAF (in the first instance) the second bad MAF I had caused the engine to stall after starting.
I can't get my CO below 3.1 % even though my HC are 261 ppm.
I can't get my CO below 3.1 % even though my HC are 261 ppm.