Another Cavalier ECU problem

Oct 11, 2004 2 Replies
I

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).



Cheers,



Iain


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A

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.

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I
*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

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