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Date:         Mon, 17 Aug 2009 11:36:26 -0700
Reply-To:     Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject:      Re: Not quite a backfire . . .
Comments: To: Rocket J Squirrel <camping.elliott@GMAIL.COM>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
              reply-type=response

The coolant temp should not drop to a very low reading during a long descent in the summer. I would be thinking about a thermostat not working correctly if I saw that on one of my vans. This is the main thing I wanted to comment on.

re With no fuel in the cylinders for so long, a > plug got fouled with oil. Unburned fuel got into the exhaust manifold and > ignited there, causing the mild explosions we heard.

Yes....backfire like sounds can be from fuel in the exhaust system getting ignited. however, by your own logic and indications observed ( 02 meter ) you believe that the throttle switch shut off all fuel to the injectors, so how could there be unburned fuel in the exhaust system, if that were true ?

that sure is a special area. They only just opened McKenzie Pass *now* ?? In August ?

on the Eugene ( west ) side of the pass, about a mile or so from the pass itself, on the north side of the road, is a delightful small lake with some campsites around it. Always wanted to camp there once. There is also in that area, another *really* nice little lake, with free unrestricted camping, with campsites around the lake. Scott turbovans ----- Original Message ----- From: "Rocket J Squirrel" <camping.elliott@GMAIL.COM> To: <vanagon@GERRY.VANAGON.COM> Sent: Monday, August 17, 2009 10:10 AM Subject: Not quite a backfire . . .

> Mrs Squirrel got a hankering to pick some blueberries yesterday, so we > took a trip over the Cascades Mountains from Bend, Oregon, down towards > Leaburg (on highway 126) to find some. For the view, we drove over the > McKenzie Pass-Santiam Pass Scenic Byway (highway 242, the Old McKenzie > Highway), which has just opened. It's an amazing road, crossing and > running next to old lava flows -- stop at the top for a cool view > (http://vulcan.wr.usgs.gov/Volcanoes/Oregon/HighCascades/dee_wright_observatory.html). > > After topping the pass, we got stuck behind a line of cars for about 45 > minutes until a flagman let us through -- ODOT was striping the new > pavement and we had to wait until the paint dried in the cool temps before > they'd let us down the other side. > > Watched a mess of small orange butterflies on the black lava rocks warm up > their wings in the sun and take short test fluttersby for the duration. > > When the flagman eventually released us we drove down the steady, winding, > hair-pinny downhill cruise of about 20 minutes. Mrs Squirrel rarely > touched the gas pedal. The auto tranny (84 Vanagon) was in 2nd, the engine > rpm-ing at about 3,000 so as to save the brakes; the smell of scorched > brakes from cars ahead of us suffused the morning air. > > Mmmm . . . hot brake pads. > > I know from previous long descents in cold temps that when there is no > pressure on the accelerator pedal, a switch on the throttle body tells the > ECU to shut off fuel, and the only source of heat for the engine is > friction resulting from being driven by the transmission. As expected, the > temp gauge dropped to nearly dead cold. The O2 meter showed pure lean > mixture: air, in other words. > > Midway down we hit a flat stretch of road about a half mile long and Mrs > Squirrel pressed on the gas pedal a bit as the van slowed and said that > nothing was happening, no engine power. There were a few mild coughs from > the engine compartment. Not loud enough to be backfires, I don't know what > those coughs are called, they were new to me. > > I suggested she press a bit harder, and the engine sped up, a bit > reluctantly, and sounded like it was missing on one cylinder. > > HERE'S MY GUESS ABOUT THAT: With no fuel in the cylinders for so long, a > plug got fouled with oil. Unburned fuel got into the exhaust manifold and > ignited there, causing the mild explosions we heard. > > When the road began to drop again, the foot came off the gas again and > fuel turned off, and the engine continued cold. A bit later we were at the > junction with the main highway. A left turn. Look left, look right, look > left again then a press on the accelerator to get up to speed and from > that moment on, the engine behaved quite normally. Temp rose up to normal > range and full "power" (if that is the correct term for what a 1.9l > provides) was available. > > So everything appears to be fine. > > -- > Mike "Rocket J Squirrel" Elliott > 84 Westfalia: Mellow Yellow ("The Electrical Banana") > 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano > Bend, OR > KG6RCR


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