400 Pre cat to lean? How to make it richer ?

[huggy59]

My 92 Griffith 400 pre Cat no other modifications AFIK): Car suffer between 1500/2500rpm of hesitations/misfiring (start/idle OK and pull like a train up to 2500rpm)

MOT guy said yesterday CO value at idle is similar to catalysed cars so too low for a pre CAT so too weak: This could explain hesitation before wide opening for butterfly. Is there a way to adjust richness?

Is AMM adjust air flow so indirectly AFR? And do you think AMM adjustment could by a way for a richer mixture? And if it is if 1V is less air so more richness ? or up to 2.3v more air so weaker ratio? Or vice versa

Who can I try to get it richer to check if hesitation desapear ?

What I have done yet without success:
- Grounds checked/cleaned
- Throttle pot adjusted by elongated holes (was out)
- Air mas meter adjusted (was very out at 2.3V with normal value at 1 to 1,5V for pre cat)..but I don't know if 2,3 make it leaner than 1V

Thanks or your help !

[Belle427]

Have you checked to see you have a tune resistor in place and it’s sound?

[huggy59]

Thanks for the head up I was not aware about them !
I found it and check it at 470ohm. This value sound right for a pre cat.




I also found this "connector" with grey/black, white/pink and white/green wire. Is that for a default code reader ?!


So unfortunatly this is not the solution...
Car was quite unloved, stored a long time and just able to start and been sold .... I have doubt about my ECU: Not sure to have a TVR chipped one or a std Land Rover (could explain why it is lean): How Can I check my ECU ?

[Steve_D]

Hi again.
That cannon 'D' connector has been fitted by some previous owner replacing the original connector for OBD. If you don't have it yet you should get yourself a copy of RoverGauge (from Blitzracing). You will need a special cable but with the other half of that Cannon connector again Blitz will be able to help you there.

470 ohm is the correct resistance for non cat vehicles also know as the green map.

Steve