Replaced AFM - now running really rich

Noddycar · Postby **Noddycar** » Mon Jan 23, 2017 10:04 pm

Hello. I replaced the air flow meter in my NA6, as the wiring looked like it had been bodgied inside (and I broke a wire cleaning it). It is now running very, very rich. The smell of petrol is quite overwhelming. Any ideas on what would cause this would be appreciated.

XMX · Postby **XMX** » Wed Jan 25, 2017 12:28 am

Was anything else moved/touched when you replaced it?
Double checked the joints in the intake pipe were 100% flush and sealed before you retightened them?
I've found even the smallest air leak can cause it to run rich.

Noddycar · Postby **Noddycar** » Wed Jan 25, 2017 7:11 am

I am reasonably confident everything is tight, but it certainly will not hurt to check again. I will re-check everything tomorrow. Apart from visually inspecting and re-tightening, is there a means of checking for a leak that does not involve specialised equipment?

Thanks for the tip. I did not think of this!

93_Clubman · Postby **93_Clubman** » Wed Jan 25, 2017 9:58 am

RX7 (S4 from memory) used a very similar AFM, which some NA6 owners upgraded to for increased flow. Is it possible you're now running one of these, ie what do you know of the history of your replacement AFM? Indeed, was the AFM even functioning correctly immediately prior to your purchase? Btw, the AFM can be tuned somewhat: viewtopic.php?t=59320

Noddycar · Postby **Noddycar** » Wed Jan 25, 2017 10:02 am

It definitely appears to be the MX5 version. The one prior to this (that I replaced) had definitely had some bodgy solder work done inside, but apart from needing a clean seemed to be OK. Well, it worked OK until I displaced one of the bodgy soldering joints....

Thanks for the link. Calibrating it may be the answer. Strangely, it seems to have settled a bit and is not running as rich today, but still quite rich in comparison to what it was previously.

93_Clubman · Postby **93_Clubman** » Wed Jan 25, 2017 11:56 am

Noddycar wrote:it seems to have settled a bit and is not running as rich today, but still quite rich in comparison to what it was previously.

If you haven't already, might be worth disconnecting the battery & pumping the brake pedal a few times to reset/clear the ECU of any fault codes. You may find after doing this that initially it runs like it initially did after replacing the AFM, but it should settle down again & may improve further due to the reset/clearing.

Noddycar · Postby **Noddycar** » Wed Jan 25, 2017 1:14 pm

Thanks for the tip. I disconnected the negative terminal while I replaced the AFM, but did not pump the brake pedal, as I was not aware it would reset the ECU. I assume pushing the pedal must do some form of mechanical reset, as without the battery connected the ECU has no power to receive a signal?

Noddycar · Postby **Noddycar** » Wed Jan 25, 2017 1:16 pm

Searching this forum is so helpful!

carsokay wrote:
Bevan wrote:I haven't heard of the brake pedal thing before, as there's no power going to anything, so it could flick any switch or anything. But yes, disconnecting the battery is the only way to reset it. Just disconnect it for a few minutes.

The reason for stepping on the brake pedal is to drain any voltage that is stored in capacitors -- primarily the big one in cars equipped with a steering wheel airbags.

That explains why you said pump the brake pedal. I will do that tonight....!