Pre-cat 3AM AFM

[griffsmith]

Hi I'm looking to test my AFM to eliminate it from a short list of potential trouble makers under the bonnet.. Being a 92 4.0L Pre-cat I have a 3AM Lucas AFM rather than the more common 5AM. This makes testing by substitution a little tricky.
Does anyone know what voltage readings I should get between pin 35 and ground.in the process as defined by the 'bible'. I believe that the 3AM reads max 3V rather than 5V for the 5AM. I presume this also effects the static and transient values???

In addition does anyone know the part number of the Throttle Pot (another suspect) again mine seems different to the norm with a round three pin connector rather than the normal square ones. I think this is the most likely suspect but can't find a new one to try!!

cheers for the help

[scoule]

You can test the throttle position sensor with a multimeter set to resistance.

One pair of pins should be contant resistance, pick any other combination and they should vary smoothly as the throttle is pressed. This is easier to spot on an analogue meter rather than a digital meter since the needle will swing relative to throttle position.

Any jumping of the needle is bad and indicates a worn track in the TPS.

Sorry, can't help with the AFM

[griffsmith]

Thanks for the post. I have tried testing the throttle pot but only with a digital meter. As you say this is over 'damped' to pick up small changes like an analogue meter would.. it did 'seem fine' although the total track resistance was about 5700 ohms, which I think may indicate the pot is suspect???

To add more intrigue to the AFM question I tested out the voltage on the AFM both as stated in the 'bible' which seemed to give reasonable figures 0.37v static to about 3.5v 'ish' full throttle.. not to far away from the expected figures for a 5AM.. but when I tested the CO trim value as defined by the RPI website I only read about 0.03v not the 1.0-1.5v expected..

more confused and a little more worried.. Still its bl**dy nice out and the car still drives ok so I'm not taking it too seriously 'yet'....

any other bright ideas anyone?


>> Edited by griffsmith on Wednesday 22 June 17:49

[griffsmith]

For those who may be interested now and in the future I have been reliably informed by the kind people of RPI that "the 3AM and 5AM are interchangeable without any ECU change" and that "they are functionally identical"..

Wow didn't expect that

so what does this mean with the voltages measured? ok for the Bible's checks pretty much as expected. However the RPI setup test on the CO trim value was 0.33 not 1.0-1.5V ????

what does the 'CO Trim' do? and what would a low or high value mean to the fueling?? does any one know? and has anyone checked /adjusted their AFM to this procedure?