Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) What Did You Do To Your Morgan Today?

Thanks for report on your investigations Tony which confirm the redundant/error checking logic used by most DBW engines. Typically the two potentiometers produce a rising and equal falling voltage around a reference in the region of 5 volts, as accelerator is pressed. These two signals when added should naturally equal the reference voltage and will throw an error code if not, P2135 in my case. The two throttle position sensors at the throttle body end are also potentiometers monitoring throttle plate position and working similarly to error check as well as providing a PWM signal to throttle plate stepper motor that tracks that from accelerator pedal, so providing a closed loop ultimately between your foot and engine power.

Unfortunately my issue is substantially different to yours though. When it happens engine still idles normally. It doesn't appear to go into limp mode as such but becomes very difficult to drive at low throttle settings and in traffic. Between misfiring and throttle hesitation it will pull very strongly but only for a second or so before misfiring. A pre-empt of the issue is often a delay for the engine to go into full trailing throttle which is easily recognised from the drone of my very vocal side pipes. This delay which is very common can last several seconds and on one occasion I was able to maintain 30 mph in a village despite foot off throttle. This may sound alarming but the instant clutch is dipped revs drop back to smooth idle albeit often with a louder exhaust note. This in turn drops to the near silent normal idle exhaust note although can take up to 10 seconds.

As I mentioned OBDII readouts show good tracking between accelerator pedal and throttle plate with engine off. Its also been confirmed visually with fast response between accelerator and throttle plate position. It was noted a fraction of a second delay before throttle plate fully rests in its idle position but this could be deliberate modulation from ECU mapping, and engine was cold and not running when making this check.

Haven't taken the car out since cleaning throttle body yet but it may take several hundred miles to show up if it hasn't cleared.