Air flow meter problem?
Discussion
Got a little problem with my Chim 400, it started hunting at idle, i cleaned the stepper motor and butterfly valve on the inlet side, this seemed to help alot but not completely. I decided to put it in for a service as it was six months since the last one anyway, the mechanic has changed the water temp sensor which has also helped but its still a bit lumpy at low revs. Mechanic has said that it may be the air flow meter, has anyone had this problem and if so are they easy to get, how much are they and is it an easy job? I have looked on the net and found what seem to be alot of upgrade versions, are they worth it or not? any help on this would be greatly appreciated.
I have played around with the airflow meter quite a bit. The is a base setting to alter the mixture be below 2500 rpm with a hex head adjustment screw on the side and The RPI web site covers checking up the DC voltages.
www.rpiv8.com/carbs-2.htm#airmass
From the RPI site:The wire colours are: Blue with Green trace = air flow signal, Brown with Orange trace = Ignition live 12 volts and Blue with Red trace = CO trim value. A digital multi meter should be used and connected to the sensor ground and CO trim value wires. The values that you are trying to achieve are below and these are adjusted by the screw on the side of the airflow meter.
To check the operation of the hot wire bit of the airflow meter, connect a meter (up to 12 volts dc) between the earth and the air flow signal output. If you remove the air filter and look at the air intake you will see a small hole on one side(This is where the hotwire is). Blow into this hole and the voltage on the air flow signal should rise fairly sharply (is in volts, not millivolts) as a rough check. The car will run without the airflow meter connected, but it runs very rich (although it should idle reasonably)and could damage your catalysts if they are hot. Its a pretty simple robust bit of kit, and not the first part I would suspect. Check all the HT stuff first.
The RPI site covers the airflow upgrades as well.
www.rpiv8.com/carbs-2.htm#airmass
From the RPI site:The wire colours are: Blue with Green trace = air flow signal, Brown with Orange trace = Ignition live 12 volts and Blue with Red trace = CO trim value. A digital multi meter should be used and connected to the sensor ground and CO trim value wires. The values that you are trying to achieve are below and these are adjusted by the screw on the side of the airflow meter.
To check the operation of the hot wire bit of the airflow meter, connect a meter (up to 12 volts dc) between the earth and the air flow signal output. If you remove the air filter and look at the air intake you will see a small hole on one side(This is where the hotwire is). Blow into this hole and the voltage on the air flow signal should rise fairly sharply (is in volts, not millivolts) as a rough check. The car will run without the airflow meter connected, but it runs very rich (although it should idle reasonably)and could damage your catalysts if they are hot. Its a pretty simple robust bit of kit, and not the first part I would suspect. Check all the HT stuff first.
The RPI site covers the airflow upgrades as well.
In my opinion the last place to start is the Airflow meter. Sadley when the Chim starts running badly it's rarly just one thing. And sometimes it's best to check right through. If you happy the Stepper motors ok I'd take a close look at the HT leads and the exstention caps. I don't like to show my age but back in the early 70's Jap motorbikes had plug caps of the same construction as the TVR plug caps. They often started to short out in no time at all. I have removed mine and taken the metal covers off. Like the old Jap items a couple of mine had contamination between the cap and the metal shield. But more importantly take a good look at the rear plug lead on the drivers side. While the cap shield may protect the cap the lead is very suseptable to heat from the exaust manifold. While the car is moving it seems ok however, when parked or I guess in traffic rising heat damages this lead. I've run my car for a considreable time like this until my new leads and caps arrive without any problems. And for the first time in months is just running perfect. I've also constructed a small heatshield to protect the lead which I hope will help. PS please excuse my spelling. Hope this helps
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