This is where I will be posting images of really bad replacement parts I come across, usually causing the same or similar symptoms as the original complaint.
This first image is a snapshot of the MAF signal from an after market, “quality assured”, replacement sensor. It was fitted to overcome an emissions complaint, where the engine was running very rich and failed the MOT.
The sensor did cure the running rich condition and the vehicle was then able to pass the MOT. However the owner then complained of a hesitation and general poor performance when loading the engine.
So I returned to the vehicle and setup a scope test of the main inputs to the ECM, including the MAF signal. Take a look.
You can see, in the image, some straight verticle lines. Take a closer look.
The owner of the vehicle paid around £200 for this sensor. A genuine sensor from Suzuki, would have cost him over £450.
This begs the question: What does the ‘QC Passed’ relate to?
This image comes from an airmass sensor that was replaced on a Vauxhall Corsa. This sensor was just a cheap aftermarket sensor, (less than £40), so no real surprises that it isn’t great. But why?
Mark Stammers Diagnostics 