EFi adjustments

G51 NAV · 21st April 2009, 19:58

Can somebody tell me what screws A, B and C set? B is blocked off on my car...presuming this to be the mixture. Guessing A and C control fast and base the idle, which I also know is influenced by the throttle-pot being accurately set to around 325mV +/- 10mV at rest.

Thanks.

henocsr · 21st April 2009, 20:34

A is mixture (co at idle)
B is idle speed screw, which is deleted on most models (why it looks blank)
C is base idle ie throttle stop screw

Adjust as follows

1 engine at temperture, then turn off engine
2 Close idle speed control valve (use fast check or ignition sequnce)
3 start engine and turn screw B fully clockwise (if fitted) to close throttle bypass
4 Adjust base idle using screw c
5 Stop engine and set throttle pot using fast check or mutimeter
6 Reconnect idle speed control valve and start engine. It should all work ok
7 set idle emissions and adjust mixture using screw A

G51 NAV · 21st April 2009, 20:59

Thanks a lot

I shall borrow my bro's gas analyser. I was warned it was running a bit rich at MOT, just within legal limits, so I shall wind it back a bit. Didn't want to mess about with the wrong screw!

Russ · 21st April 2009, 21:11

You will need to set the stepper motor and throtle pot as well John

G Force · 22nd April 2009, 10:07

Quote:

Originally Posted by G51 NAV

Thanks a lot

I was warned it was running a bit rich at MOT, just within legal limits, so I shall wind it back a bit.

Hi G51 NAV, I know you might not of mean't the above literaly,

but just to clarify for yourself and others.

Screw A is screwed out to weaken the mixture at idle (anti-clockwise).

Ps If you are going to attempt the full set-up procedure, for best results it is best carried out after cleaning all the gunk from inside the throttle body.

G51 NAV · 22nd April 2009, 11:23

Cheers Gary. Yes, quite right. I've still got the sod-off-sized spanner I bought to remove the stepper-motor when I last stripped one of these down some years ago. Nearly all the running problems on these cars are caused by gunked-up internals.

G51 NAV · 25th April 2009, 20:53

Spent some time sorting this today: de-gunked, throttle-pot set, idle CO set and idle-speed set.

Throttle-pot was adjusted to give over 500mV at idle

Of course when I took it down to 320mV the car stalled: throttle-stop was all to pot as well!

CO was indeed highish at 4%. With the gas-analyser out of sight at the other end of the car, I had a go at setting the mixture using the old tried and tested 'by ear' method (difficult to train someone to do this: you either can do it or you can't; my experience goes back decades). Very pleased that when set at what I perceived to be the best mixture, a trip down to the other end of the car showed a much improved 2.4%. As little as a quarter turn either way had a detrimental effect on the smoothness of the idle, so that's where it stays.

The recommended setting is 1.9%-3.5%. With 22 years and 52k under its belt, I think it's doing very well to be running best at only 0.5% over the minimum.