Quote:
Originally posted by AlexO:
Since I have had it back on the road, my 914 has been running really rich from idle to 4500 or so. It is a '74 2.0 with a cam larger valves, and Bursch collector but stock EFI. My plugs are black, and i get a decent (not too big) puff of smoke if i snap the throttle off idle.
I have set the fuel pressure a little low (26-27psi), and the CO screw seems to have no effect. Any ideas?
--Alex
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Pull a vacuum of 15 in. Hg or so on your MPS input port and make sure it isn't leaking (leaking = rich). What kind of cam are you using? Only the mildest improvements in lift and duration over stock will work properly with the D-Jet system. Bigger valves should increase volumetric efficiency somewhat - which the D-Jet ECU won't know about, so it would tend to make your mixture
at a given engine speed (more air in @ same injection duration = leaner).
Low fuel pressure will cause a leaner mixture, since the injection quantity is directly related to the fuel pressure at a fixed injector flow rate.
I assume the "CO screw" you describe is the ECU idle mixture knob. Changes to this adjustment only affect the mixture at idle and during overrun conditions (where the engine speed is >2000 rpm). The knob has no effect at part-load or full-load.
Jim suggested checking how it runs with TS1 disconnected. If it's already running rich, disconnecting TS1 will make it somewhat richer. Shorting TS1 will make it run somewhat leaner. TS1 accounts for air density changes with temperature and produces a second-order effect on the ECU's calculation of the injection duration.
You should verify that you have all of the correct D-Jet parts for your engine as Jeff Bowlsby suggested. I'd also check on his suggestions about leaky injectors or the CSV. Note that if the control lead to the thermoswitch is touching any metal and is grounded, that the CSV will be activated and you'll get a rich mixture.
A final suggestion is that if you can't figure out what's going on, rent the VW 1218 tester from Pelican Parts and test the system out.
Brad Anders
[This message has been edited by pbanders (edited 07-10-2001).]