Idle knob on ECU, uhhh, which way do I turn it again? |
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Idle knob on ECU, uhhh, which way do I turn it again? |
RoninEclipse2G |
Oct 29 2007, 11:34 AM
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#1
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Suby Geek Group: Members Posts: 232 Joined: 28-April 07 From: Parker, Colorado Member No.: 7,701 Region Association: Rocky Mountains |
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. |
jbyron |
Oct 29 2007, 12:55 PM
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#2
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Jamie Group: Members Posts: 128 Joined: 17-July 07 From: Ballwin, MO Member No.: 7,916 Region Association: Upper MidWest |
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! |
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