Road Speed Sensor

[john p]

Recently my Chim has stopped popping and banging on the overrun,it also feels like you are driving with a choke out.If you dip the clutch whist moving,the rev counter shows about 1200 rpm.When coming to a stand the revs don't drop until you've been stationary for a couple of seconds.I've cleaned the stepper and its housing and also the throttle and road seed sensor but it's still the same.It's a 1993 4.3,the car drives fine but I want my pops and bangs back,any ideas anybody?

[blitzracing]

Check the airflow sensor connection. The car will still run without it connected at all, but runs very rich. I assume you have not touched the mixture scaling screw on the air flow meter? If this is out it can make the car run very rich, but dont just tweek it to find out, as some other fault is more likely. Also if the ECU picks up on a failure and runs the get you home map, it will hold the Idle RPM higher to stop the cat' getting damaged. If you have an ECU fault light this should be on if it is running get you home mode.

[Griffit]

blitzracing said:

Check the airflow sensor connection. The car will still run without it connected at all, but runs very rich. I assume you have not touched the mixture scaling screw on the air flow meter? If this is out it can make the car run very rich, but dont just tweek it to find out, as some other fault is more likely. Also if the ECU picks up on a failure and runs the get you home map, it will hold the Idle RPM higher to stop the cat' getting damaged. If you have an ECU fault light this should be on if it is running get you home mode.

Mine has started doing almost the same thing too. Holds about 1500rpm until the car comes to a halt. IS this likely to be the same problem? Not sure if it started when I moved the ECU to charge the battery, I suppose it's possible that I've dislodged something?

[andy-w]

blitzracing said:

The car will still run without it connected at all, but runs very rich.

i disconnected mine once with the engine running and i couldnt have stopped the engine any quicker if i had switched the ignition off!!!

[john p]

blitzracing said:

Check the airflow sensor connection. The car will still run without it connected at all, but runs very rich. I assume you have not touched the mixture scaling screw on the air flow meter? If this is out it can make the car run very rich, but dont just tweek it to find out, as some other fault is more likely. Also if the ECU picks up on a failure and runs the get you home map, it will hold the Idle RPM higher to stop the cat' getting damaged. If you have an ECU fault light this should be on if it is running get you home mode.

There are no fault lights and everything else seems to be spot on,it's just different to how it used to be.

[blitzracing]

Ive not tried pulling the airflow meter off while its running, but if its disconnected before start up it will run. Its probibly the get you home map doing it. I think it would be worth while checking the DC voltages. It makes a huge difference on mine, but I dont run catalysts / lamda sensors or the catalyst map on the ECU, so there is nothing else tweeking the mixure apart from this base scaling. Its different on the catalyst map (only up to 2500 rpm) as the catalyst map tries to adjust the mixture to keep the emmisions low. Above 2500 rpm it goes "open loop", so the I would think the base setting makes more of a difference.

A bit here:
http://www.g33.co.uk/fuel_injection.htm

[john p]

Went for a long run yesterday,and the car returned to normal after about 1 hour,I think i'll put it down to lack of use.