Boost Leak...How Do I Locate?
05-16-2007, 04:32 PM
#16
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The 930 operates under vacuum at idle. It continues to operate under vaccum until the turbo generates enough positive pressure to get back to zero then boost builds.
Leonard
Leonard
05-17-2007, 09:10 AM
#17
Burning Brakes
Thread Starter
Originally Posted by Mark Houghton
Another thing to be aware of is that if any of the orange O-rings fail and allow boost air to leak, it will affect your AFR somewhat at idle. If the leak is bad enough, it will cause a stumbling idle, because your vehicle will be running richer than it should (that leaking air is supposed to make it into the combustion chamber). Remember, with CIS the fuel addition rate has already been determined by the volume of air moving across and deflecting the plennum. And if all that air doesn't make it to the combustion chamber (i.e, it leaks out somewhere via a bad o-ring), things will be too rich. You should know right away via poor idle. This happened to me once when I was setting up my boost control and went just a wee bit too high, causing the overboost protection circuit to shut everything down. If you haven't experienced this, it's rather violent as the fuel shuts off...then starts right back up after the boost is bled off. It caused one of my o-rings to dislodge, and the car ran like crap and would barely idle.
At a red light/idle, my rpms will "hunt", ie the car will dip to 500 rpms then speed itself up to 1500rpms and repeat this process OVER and OVER again until I get it moving. ANNOYING AS HELL.
This could be all related somehow. I know that I had the AFRs checked a couple of months ago, but when he checked, I know for a fact that the car was not hunting during idle, and I don't think that it was stumbling under less than full throttle on boost either...
05-17-2007, 03:15 PM
#18
Burning Brakes
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However, I have been corrected in my earlier hypothesis regarding intake pressure during idle. In fact, the intake is under negative pressure (vacuum) at idle. The hunting you're experiencing sounds clearly like a mixture issue. Search this forum for more info; I think I even started a log on this topic a year or two ago, because I was experiencing "hunting" not at idle, but at constant low speed in 2nd gear city driving. The damn thing would "surge" plus or minus a couple hundred rpms just tooling down the road under no load. I finally bought a CO meter and found my mixture was way off (I THINK it was rich, but my mind has since fogged). A simple adjustment was all it took.
You're issue may be related to the WUR, as it does adjust fuel pressure dependant upon engine temperature. Cooler running engine in the winter, vs summmer....perhaps the WUR is acting up.
You're issue may be related to the WUR, as it does adjust fuel pressure dependant upon engine temperature. Cooler running engine in the winter, vs summmer....perhaps the WUR is acting up.
