From: darling@simlab.arc.nasa.gov on behalf of Dave Darling [darling@simlab.arc.nasa.gov] Sent: Wednesday, April 14, 1999 3:52 PM To: pelicanparts@csi.com Subject: Re: [914] Running over rich >Date: Wed, 14 Apr 1999 15:51:17 -0700 >To: Alex O'Connor >From: Dave Darling >Subject: Re: [914] Running over rich >Cc: "914" <914@rennlist.org> >Bcc: >X-Attachments: > >At 3:31 PM -0700 4/14/99, AlexO35@aol.com wrote: >> Well, I finally gave in and took my car into teh shop today. The tech >>I've got on it had it running in an hour and a half. The problem is, it >>runs >>*way* to rich. It spewed tons of smoke out the exaust. Its so far out of >>adjustment that the PCM knob won't help. The fuel pressure is at 31 psi. >>What sensors does the PCM rely on to determine the mixture at startup? > > The mixture is determined by the manifold pressure (as measured by >the MPS over on the right-hand side of the engine bay), by the head temp >sensor (by the #3 spark plug), and by the intake air temp sensor (located >on the manifold itself). At idle, slightly different stuff happens, but I >think that all of those things still do affect the mixture. At idle, the >knob on the ECU also affects mixture. (And *only* at idle.) > First suggestion is the ignition system. Make sure you're getting >a good healthy spark, points and condensor are good, timing and dwell are >in spec. (Bad points caused similar problems for me once.) > Next, check the resistance of the head temp sensor. 1500-2500 ohms >cold, ~100 (?) when the engine is warm. More resistance means a richer mix- >ture. Check the MPS--make sure that it holds a vaccuum. Check the hose to >the MPS for breaks, cracks, leaks, etc. > 31 PSI fuel pressure is a little high, which will make the mixture >a little rich--but it shouldn't be enough to cause your symptoms. > If the intake air temp sensor is unplugged, the engine will also >run a little rich--but again probably not to the point yours seems to be. > An MPS that has been "adjusted" can significantly change the mixture. >As can the incorrect one. (For instance, a VW Type III one made my engine >run VERY rich--about like you describe.) > > There are probably more possibilities, but those are all off the >top of my head. > >--DD > Dave Darling 74 914 2.0 (VROOM!) darling@simlab.arc.nasa.gov <--- OR ---> ddarling@wgss.com "914: The Porsche Picnic Basket. A lid that opens on each end, and a handle in the middle.." -- CHD