Tannaton
Active Member
- Posts
- 288
- Location
- Beverley, East Yorkshire, UK
Should say I have no idea about these things, just being nosey really
If there is a tuning box in the system - it must be a pretty poor one! Trying to play around with idle doesn't sound like a very sensible thing to do to me.
With all these different MAFs showing the wrong but consistent value it would indicate the wiring has an issue or possibly the ECU itself - ie the Pin in for the MAF reading. Difficult job to try another ECU though as you'll need the CCU swapped over as well and possibly the immobiler ECU (something leads me to believe its separate to the CCU on TD4?). Not sure if the MAF feed is a variable voltage or pulse - if its pulse you're going to need an oscilloscope presumably. Reading Rave on my L Series, I know some of the ECU signals are voltage and others pulse.
However, the ECU does appear to recognise correctly when the MAF is disconnected. The engine should run OK with the MAF disconnected - therefore if the misfiring is still occurring, it would indicate that the problem is not related to the MAF.
Yep agree with all that. I've seen cheapo tuning boxes before which are just a resistor or something to fiddle the sensor reading. Same as driving a old petrol car with the choke out and saying you've souped it up...
But yes, the ECU can detect when the MAF is there or not. The MAF is a potential divider so there is a +ve, -ve and a signal, so it should be possible to diagnose with a voltmeter.
I also agree with your other suggestion here - this is very likely more than one problem, I think the MAF reading is not related to the smoking and misfire. In my mind that is likely to be a injector fault as I expect that general over fuelling on an unloaded engine across all cylinders would cause the revs to rise? If I can't trace it to an injector I will be borrowing and oscilloscope to check the injector pulse and fuel pressure stability...
