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Date:         Wed, 25 Apr 2007 13:50:34 -0500
Reply-To:     Matt Roberds <mattroberds@COX.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Matt Roberds <mattroberds@COX.NET>
Subject:      Re: backfiring?
Comments: cc: craig cowan <phishman068@GMAIL.COM>
In-Reply-To:  <20070425033251.PBCF5.eastrmmtai101.cox.net@eastrmimpi03.cox.net>
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed

> From: craig cowan <phishman068@GMAIL.COM> > Date: Tue, 24 Apr 2007 22:30:55 -0400 > > So, with a new distributor in place, and the timing set to as close as > we seem to be able to get it (though it sitll could be off), the engine > runs with considerably less power than it had before. [...] After > doing this a few times, i realised that when i hit the gas fast, there > is a distinct popping or hitting sound from the right side of the engine > that truely sounds like its coming from inside the intake mainfold/rubber > piece coming from the airfilter box.

A couple of random ideas...

I have had fuel injected engines behave like this when there was a vacuum/intake leak between the air measuring device and the engine. Slamming the throttle open makes them almost die, but gently opening it up will more or less keep it running. You might check vacuum hoses, rubber boots, etc.

How did you set the timing on the new distributor? Why do you think it may not be right? One thing you could do (for diagnostic purposes) is to make a match-mark on the distributor and its mounting, so you can get it back in the same place, then twist the distributor maybe 1/8" (3 mm) one direction from the mark and run the engine again. DON'T DRIVE THE VAN LIKE THIS, just run it for a minute or two in the driveway. If 1/8" one way makes things worse, put it back to the mark, and then go 1/8" the other way. If you really can't decide, you might go another 1/8" (1/4" (6 mm) total away from the match-mark) but not any further than that. Again, DON'T DRIVE LIKE THIS - this is just a simple test to find out if timing is a large part of the problem. If turning it _does_ help, it's time to get the timing dialed in correctly, like by taking it to a shop, borrowing a timing light, etc. The reason you don't want to drive it like this is that it is possible to adjust it to sound and feel great at idle and at high RPMs under no load, but when you put a load on it while driving, it will ping/detonate like crazy, which is bad for the engine.

The new distributor is the same part number and all as the old one, right?

Matt Roberds


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