Re: Another Cavalier ECU problem

[Anthony Britt]

"Iain McLaren" <iain@nospam.com> wrote in message
news:416ad741$0$22762$db0fefd9@news.zen.co.uk...
> Hi,
>
> After just getting my alternator (and bulb) changed, my ECU light is on
> again :-(
>
> It only comes on for a second or so when it does - usually while coasting.
> The 'blink' code is 7-3 which apparently means an airflow sensor low
> voltage.
>
> I've looked on the air-intake side of things and there seems to be
> pitot-type sensor just after the airbox, and then what I presume is an air
> temperature sensor just up from it a bit. Is what I think is a pitot the
> only sensor? On the engines in the Haynes it looks like there's one nearer
> the fuel-injection manifold, but my engine's a 2.5 which ain't covered
> (Grrrr).
>


The first sensor from the airbox is the intake air temperature sensor, the
next is the mass air flow meter. For the low voltage code to come on when
coasting , it means that the output voltage from the air flow meter is
dropping to 0v, representing zero airflow through the engine. This can be
due to either a dirty sensing element on the MAFM (take off and clean out
with carb cleaner), a sticking idle control valve (remove, clean and
lubricate with a little WD40) or a dirty throttle butterfly (there should be
a minute gap around the edge of the throttle valve with the throttle against
the stop screw - the build-up of gunk around the throttle body can obstruct
this gap). Does the vehicle have a fluctuating idle speed at all, or is it
quite constant?

HTH

Anthony
Remove eight from email to reply.

[Iain McLaren]

*Well*.... It only started coming on after I had a semi-service performed,
part of which was to replace the air filter (which they weren't originally
going to do and it looked clean enough to me when I took it off a few weeks
ago). Maybe it's not letting enough air through??? Maybe it's not a genuine
Vaxhaull part - does the V6 get a different filter than, say, a 2.0 DOHC
model?

It was running fine at idle when I drove it at the weekend, but I'll have to
check again - or ask the Mrs (she gets to drive it while I get stuck with
the Escort!).

Since its 'service' it's now leaking oil from the sump plug even though it
appears to be tight enough, so I'll need to go and have a 'word' with the
garage anyway....

And here's me thinking that giving someone else the work would be
easier.....I'll just have to dig out my overalls next time and not be such a
lazy sod!

Cheers,

Iain


"Anthony Britt" <anton_600@8msn.com> wrote in message
news:usDad.991095$yk.166437@news.easynews.com...
>
> The first sensor from the airbox is the intake air temperature sensor, the
> next is the mass air flow meter. For the low voltage code to come on when
> coasting , it means that the output voltage from the air flow meter is
> dropping to 0v, representing zero airflow through the engine. This can be
> due to either a dirty sensing element on the MAFM (take off and clean out
> with carb cleaner), a sticking idle control valve (remove, clean and
> lubricate with a little WD40) or a dirty throttle butterfly (there should
> be
> a minute gap around the edge of the throttle valve with the throttle
> against
> the stop screw - the build-up of gunk around the throttle body can
> obstruct
> this gap). Does the vehicle have a fluctuating idle speed at all, or is
> it
> quite constant?
>
> HTH
>
> Anthony
> Remove eight from email to reply.
>
>

[churchill53]

Hi All,

I have a similar problem with my CDX Auto, which results in the engine management light being on at idle and when coasting, but going out when accelerating past about 1000rpm?

I am told that the rocker cover breather tube could also be blocked, and requires cleaning.

I am going to try these solutions this week, and will post result for future reference.

Many thanks

Andy