[928uk] Engine hunting at idle

[Paul Smith]

A steady idle and good pick-up are the criteria I prefer over a number from
a potentially inaccurate machine. I have never had any success with a
domestic exhaust gas analyser.
Smiffy

On Wed, 13 Jul 2022, 13:33 jeremy lane via 928uk, <928uk at lists.928.org.uk>
wrote:

> That’s very interesting Mike - I have to say my car is running better than
> ever so I won’t be changing anything while it continues!!
>
> Jeremy Lane
> 07971671887
>
> On 12 Jul 2022, at 19:31, Michael Parris <michaeljparris at gmail.com> wrote:
>
> 
> Thanks Jeremy,
>
> It's worth noting that 1% CO is about right, 1.5% is a little rich.
> That's at correct engine temp and no accessories running plus air pump
> plugged if one is installed.
>
> The 4.7L S2 LH-JET cars with MAF are usually set a little richer than 1% -
> this is done with the adjuster on the MAF itself - same for US 5L 32V
> 'organ pipe' motors.  Idle speed may need to be adjusted after.
> The early S4/GT/SE disconnected the wire from the adjuster on the MAF and
> it's now found to the right of the ABS ECU above the CE panel. Clockwise
> makes it richer so when a new MAF is fitted I suggest 3 turns anti-clock in
> case it's been adjusted for the previous worn MAF or check Ohms across it
> and set to 380R
> If your 928 has cats or an oxygen sensor they sort themselves out but it's
> important that the ECUs are reset with a battery disconnect when a new MAF
> is fitted.   The WSM says run idle adapt with a Bosch hammer or similar but
> it will adapt by itself after about 10 minutes of mixed driving.
>
> The above is useful if the car starts to run poorly and you can find a
> place with an exhaust gas tester to see if it's the mixture and bring it
> back in spec. but obviously not on a car using an O2 sensor.  The adjuster
> doesn't have a stop by the way so when it gets to 1K Ohms and it still
> isn't rich enough then that's it, the MAF is done and needs to be rebuilt.
> On the S2 the wear limit is 2%, the later cars are more generous at 3%
> worn. It doesn't sound like much but it doesn't take much air fuel ratio
> difference for them to run poorly, hesitate and lack power.
>
> Regards,
> Mike
>
>
>
> On Tue, 12 Jul 2022 at 13:09, jeremy lane <jfl46 at hotmail.co.uk<mailto:
> jfl46 at hotmail.co.uk>> wrote:
> Sorry Mike - 1988S4
>
> Jeremy Lane
> 07971671887
>
> > On 12 Jul 2022, at 13:00, 928uk-request at lists.928.org.uk<mailto:
> 928uk-request at lists.928.org.uk> wrote:
> >
> > Send 928uk mailing list submissions to
> >    928uk at lists.928.org.uk<mailto:928uk at lists.928.org.uk>
> >
> > To subscribe or unsubscribe via the World Wide Web, visit
> >    https://lists.928.org.uk/mailman/listinfo/928uk
> > or, via email, send a message with subject or body 'help' to
> >    928uk-request at lists.928.org.uk<mailto:928uk-request at lists.928.org.uk>
> >
> > You can reach the person managing the list at
> >    928uk-owner at lists.928.org.uk<mailto:928uk-owner at lists.928.org.uk>
> >
> > When replying, please edit your Subject line so it is more specific
> > than "Re: Contents of 928uk digest..."
> >
> >
> > Today's Topics:
> >
> >   1. Engine hunting at idle then stalling when hot (jeremy lane)
> >   2. Re: Engine hunting at idle then stalling when hot (Michael Parris)
> >
> >
> > ----------------------------------------------------------------------
> >
> > Message: 1
> > Date: Mon, 11 Jul 2022 17:26:47 +0000
> > From: jeremy lane <jfl46 at hotmail.co.uk<mailto:jfl46 at hotmail.co.uk>>
> > To: 928 List <928uk at lists.928.org.uk<mailto:928uk at lists.928.org.uk>>
> > Subject: Engine hunting at idle then stalling when hot
> > Message-ID:
> >    <
> DB6PR0601MB2358153A357829A476BF686CF0879 at DB6PR0601MB2358.eurprd06.prod.outlook.com
> <mailto:
> DB6PR0601MB2358153A357829A476BF686CF0879 at DB6PR0601MB2358.eurprd06.prod.outlook.com
> >>
> >
> > Content-Type: text/plain; charset="us-ascii"
> >
> > I have had my car for  6 years and I thought this problem had been
> solved by Cambridge OPC some years ago but it has misbehaved intermittently
> since.   Unfortunately in the recent weather the problem came back with
> avengeance and I delivered the car to Autofarm near Bicester.  Their 928
> time served technician Mark has finally sorted it.  It turned out to be a
> fuel mixture CO% issue - should be 1.5% and mine was only 0.5%.  This was
> adjusted twice and re measured to the correct mixture.  Today was a full
> test in ideal conditions and the car has performed perfectly.  I know
> others have mentioned having the same or similar problem so this is worth
> checking.
> >
> > Jeremy Lane
> > 07971671887
> >
> > ------------------------------
> >
> > Message: 2
> > Date: Mon, 11 Jul 2022 18:57:46 +0100
> > From: Michael Parris <michaeljparris at gmail.com<mailto:
> michaeljparris at gmail.com>>
> > To: jeremy lane <jfl46 at hotmail.co.uk<mailto:jfl46 at hotmail.co.uk>>
> > Cc: 928 List <928uk at lists.928.org.uk<mailto:928uk at lists.928.org.uk>>
> > Subject: Re: [928uk] Engine hunting at idle then stalling when hot
> > Message-ID:
> >    <CAAHHLpLmPAGT5+wU+LbU2pN5zUtqYvuMzbPPDeoPk152pRZNVg at mail.gmail.com
> <mailto:
> CAAHHLpLmPAGT5%2BwU%2BLbU2pN5zUtqYvuMzbPPDeoPk152pRZNVg at mail.gmail.com>>
> > Content-Type: text/plain; charset="UTF-8"
> >
> > What year is your car?
> >
> > Mike
> >
> >> On Mon, 11 Jul 2022, 18:26 jeremy lane via 928uk, <
> 928uk at lists.928.org.uk<mailto:928uk at lists.928.org.uk>>
> >> wrote:
> >>
> >> I have had my car for  6 years and I thought this problem had been
> solved
> >> by Cambridge OPC some years ago but it has misbehaved intermittently
> >> since.   Unfortunately in the recent weather the problem came back with
> >> avengeance and I delivered the car to Autofarm near Bicester.  Their 928
> >> time served technician Mark has finally sorted it.  It turned out to be
> a
> >> fuel mixture CO% issue - should be 1.5% and mine was only 0.5%.  This
> was
> >> adjusted twice and re measured to the correct mixture.  Today was a full
> >> test in ideal conditions and the car has performed perfectly.  I know
> >> others have mentioned having the same or similar problem so this is
> worth
> >> checking.
> >>
> >> Jeremy Lane
> >> 07971671887
> >
> >
> > End of 928uk Digest, Vol 276, Issue 11
> > **************************************
>