ok, so I tried searching (the search tool is a bitch here) but I seem to remember reading somewhere on here someone mentioning that the haynes manual had the directions for adjusting the idle knob on the ECU for a D-jet was backwards.

I just finally got some nasty vacuum leaks fixed and now I can adjust the idle all I want (YAY!) but it seems to be running rich and I don't want to make it worse. I can smell the raw fuel in the exhaust, and I know that I have exhaust leaks but since I fixed the vacuum leaks it's popping 3-4 times as much now especially on downshifts.

why do you want or need a potentiometer to adjust idle? If you are putting it inline with the CHTS that will adjust the mixture at startup but once the motor reaches operating temp. the CHTS is ignored. The biggest misconception is that the CHTS is used throughout all temp ranges and is a integral part of idle adjustment all the time.

If the CHTS where bad and going in and out of range this would make the car run rich becaouse the ECU thinks the motor is cold.

A potentiometer would be good to have to be able to sync. CHTS enrichment with the AAR.

There should be a idle adjustment knob on the ECU.


How is your fuel pressure?

Have you checked the MPS?

I was meaning the idle adjust knob on the ECU, the haynes manual calls it a potentiometer.

thought I had a problem with the MPS for a bit, but now that I fixed the vac leak, it seems to be functioning properly.

the issue is that I had a nasty hunting idle and it would die right after startup, also I couldn't adjust the idle down below 1800 rpms. I changed the throttle spring cause it was sprung, and put a new secondary spring on the return and fixed several vacuum leaks. all of a sudden it starts right up when it's not too cold out and idles right at 1100 rpms cold and drops to 900 once it warms a touch.
once it gets warm, it starts popping a bunch. I know of the exhaust leaks, unfortunately the only thing that will fix those is money I don't have (new muffler/gaskets)
if I have a little fun and get things hot it starts wanting to stall out and I can take care of that by backing out the idle screw and raising the idle.

that's why I'm thinking I need to use the idle adjust knob to lean it a touch

From an article by Kjell Nelin. Hope it helps.

Adjustment and Modifications -
There are several mixture adjustments possible with this system. The easiest is to simple adjust the knob on the top of
the ECU ('72 and later). This will fine tune the idle mixture only. Here's how you can make major changes in the
mixture (if the engine is getting worn or if you have changed cams, or displacement during a rebuild). Some people
recommend changing to the 2.0L injectors if a 1.7L is bumped up to 1.9L, however I have found this to be
unnecessary if the stock cam is retained.
First, remove the pressure sensor. You will notice a large plug with a slot in it sealed with epoxy on the end of the
unit. Heat the epoxy (I use a heat shrink gun but a powerful hair drier should work) and scrap it away with a
screwdriver. Once the slot is clear, turn the plug in a bit and remove the epoxy from the threads. Continue turning the
plug out then in and scrape the epoxy away until you can remove the plug. Allow the unit to cool. You will see an
adjusting screw inside the pressure sensor.
Mount the sensor in the car with the access hole pointing up so that you can see the adjusting screw. Turning the
screw clockwise will lean out the mixture, counterclockwise will make it richer. Ideally, use a CO meter or an O2
(lambda) sensor to set the mixture. Set the mixture to 2.0 - 2.5 % CO at 2,500 RPM. I use a single wire O2 sensor
mounted on the exhaust system on my 1.9L which gives me the instantaneous air/fuel ratio at all times, even while
driving the car.
You can set the mixture "by ear" if you must. Make sure the engine is up to normal operating temperature. Run it up
to 2,500 RPM and hold it there, adjust mixture for the smoothest sounding running. This will set the overall mixture.
Turn off the engine, install the plug and mount the pressure sensor as normal. Now, to set the idle mixture, try turning
the adjustment on the top of the ECU, clockwise enriches in this case.
If the idle "hunts" when turned up all the way it is too lean. Do the following, get a 2,000 ohm variable resistor
("pot") and install it in series with the Temp Sensor II (in the head). Set the ECU idle adjustment at the middle of its
range. Starting at zero ohms adjust the pot with the engine running (again, at full operating temp) until the idle
smoothes out or the CO reads about 1.5 - 2.0 %. Shut off the engine, remove the pot and measure the resistance. Get a
fixed resistor near this value and install permanently.
Finally, adjust the idle mixture with the ECU adjustment and set the idle speed with the air bypass screw at the
throttle body. Lastly, drive and enjoy your rejuvenated 914 for many years to come!

Thanks, I think that will help

The ECU knob is what you want to adjust
it affects idle only.

I would recommend NOT adjusting the MPS screw unless you have a wideband sensor.

the large cap screw is also a diaphram stop and if you get it wrong you will tear the diaphram in short order.

if your car is rich and smelling rich, then it is likely your MPS is already half torn.
vacuum test your MPS
if it vacuum test's correctly, then do not adjust it.
or send it to one of the members here that has a wide band to have it adjusted safely.

if you fail the vacuum test, then that would account for the rich mixture.
I have a perfect/tested MPS for sale if needed.

the ECU knob only affects the mixture at idle.
good for passing the idle sniff test.
use the idle adjustment screw to bring up/down your idle in most conditions.