The same switch contacts are used for both closed and open throttle with the combination of RPM and AFM position being used to tell the difference. The switch should be closed (0 ohms) at full or closed throttle. It needs to open fairly quickly when the throttle is opened. Some of the behavior you noticed is normal. When the throttle is closed and the engine is being overrun the fuel injectors actually turn off. The causes a number of things to happen including the cylinders going cold during extended closed throttle operation. Now for the tricky part. As the throttle is opened or the overrun goes away and the injectors resume operation the O2 sensor is ignored for some time. This is where correct baseline settings are so important. If the mixture is off and the system relying on O2 sensor trim all the time there will be an additional delay before things work right. Of course if traveling and changing altitudes the correct mixture at sea level will not be the same at 8,000 feet so O2 sensor trim will be used much more. Also keep in mind that at 8,000 feet your engine has lost 24% of its available horsepower Dennis . -----Original Message----- From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Don Hanson Sent: Sunday, March 10, 2013 9:44 AM To: vanagon@GERRY.VANAGON.COM Subject: Throttle stop switch? Stumbles on resume throttle.. I have a Digifant ignition on a 93 Jetta inline gas powered van.. When I coast down a long grade at higher RPMs (highway speeds) there is often a slight hesitation as I resume pushing on the gas pedal...This hesitation can be more pronounced at high altitude, I think. Recently, at over 8000' elevation I felt an almost "engine off" delay of perhaps a full second when I reached the bottom of a slope and put my foot back on the pedal. If I keep a very slight amount of throttle open, there is no hesitation. Another diagnostic symptom (could be exacerbated by a small crack in my exhaust downpipe) is that rarely, my exhaust will "Pop!" loudly a single time when I drop throttle at lower rpms. This 'delayed throttle response' was particularly un-nerving as I was descending a very slick and windy snow-covered pass recently..."exciting moments" as the engine resumed drive after descending slowly in a lower gear... I have a switch that looks somewhat thin and flat, with a leaf-spring/bent lever looking prong that is activated by a small post in the linkage near my throttle body. I assume that is the throttle stop switch. It seems to activate (mechanically) properly...it "click" when you just crack the throttle and 're-clicks' when you release the throttle... I can't decipher my 2 Bentlys (Vanagon and Cabriolet) well enough to even figure out which switch I have and how to go about testing it. There seems to be a couple of very different ones used on various Digifant systems. Can someone guide me as to how to test this part? Does anyone have any other ideas as to what might be causing this somewhat troublesome delayed throttle response? Don Hanson |
Please note - During the past 17 years of operation, several gigabytes of
Vanagon mail messages have been archived. Searching the entire collection
will take up to five minutes to complete. Please be patient!
Return to the archives @ gerry.vanagon.com
The vanagon mailing list archives are copyright (c) 1994-2011, and may not be reproduced without the express written permission of the list administrators. Posting messages to this mailing list grants a license to the mailing list administrators to reproduce the message in a compilation, either printed or electronic. All compilations will be not-for-profit, with any excess proceeds going to the Vanagon mailing list.
Any profits from list compilations go exclusively towards the management and operation of the Vanagon mailing list and vanagon mailing list web site.