Right after fitting my Innovate Motorsport Wideband AFR Guage, I have been impressed with the results but concerned with my fuelling a little.

On normal idle I am getting 14.7 AFR which is pretty good going TBH. it sometime drops a little leaner which I believe is a slight missfire problem which I am trying to sort.

When driving, I notice I am generally in the 12.0 - 14.0 AFR range which is a bit too rich bit it does start to lean off slightly when boosting.

But If I want to stay at a steady speed, i.e.80 MPH, i notice that the AFR goes down to 10.0 AFR which is very rich but if I accelerate it goes back to 12.0-14.0AFR level. I also notice a smell of fuel. This accounts for my recent poor fuel economy, also this is whithout boosting i.e sat at
-20hg/cm??? (cant remember unit of measurement)

I am running a boost pressure fith injector which would account for the rich top end at high boost (7 psi boost input for injector, car held at 12psi at the mo)

I have reviewed a bosch tech book I have but cant seem to find which what casue this.

Initial thoughts are:

1. TPS. Might need adjusting or have a loose wire.
2. Fuel pressure actuator (might be on its way out, can see why tho!)
3. Fuel ECU (seems to be getting power)

The car has a reasonably tuned bottome end, lightened balanced etc, stage 3 big valve head etc. Cosworth housing and T3 turbo.

The car runs fine apart from a miss fire / popping when I decelerate and the AFR leans off. (Sounds like its running on 3). Its had new leads, plugs, coil change, dizzy cap, rotor arm etc.

Any help would be appreciated.

I am going to adjust the fuel pressure regulator first to lean it out a bit. That might help. Now which way do I turn the screw?

 

The TPS isn't actually a true sensor its 2 switches, it tells the fuel ECU of absolute idle and full open throttle, anything other than those 2 states aren't sensed by the ECU.

Chances are your EMFPR needs adjusting.