Date:         Sun, 20 Oct 2019 10:44:43 +0000
Reply-To:     Stephen Grisanti <bike2vcu@YAHOO.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Stephen Grisanti <bike2vcu@YAHOO.COM>
Subject:      Another case of stumble/loss of power after warmup
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I followed the previous "acceleration/excelleration" thread at the time and reviewed again when my own van's symptoms cropped up this week but found no resolution.  Stock '87 2.1 with manual trans, 93,xxx miles, seldom driven these days, tank needs reseal but weather has been very dry. Replaced fuel lines several years ago.
We've had occasional instances of this behavior, usually about once in 20 cold starts.  Start the van from cold and once it warms up (about five minutes or until we get out of the neighborhood) it will develop a stumble and refuse to rev over 3,000 RPM.  Turning the key off and restarting has been the fix before now.  The van has been parked for several weeks while we work on a big landscaping project and was long parked before that until we moved it around the drive for access.  Our camping has suffered in the last couple of years and the van rarely gets 300 miles a year lately, and I try to start it weekly but realize I'm probably shutting down before this problem has a chance to manifest. Van got a dose of Seafoam in the last tank. 
Most recently the bride was at a seminar so I thought I'd play a little.  Cranked it up and let it warm up, then drove around the neighborhood and the stumble began.  Ordinarily I'd switch it off and restart while rolling and would continue with no further issue but this time the stumble returned shortly after restarting. I continued driving, hoping it would clear up, but it only cleared up when I switched it off and restarted.  Did this repeatedly and the stumble always occurred again and persisted. Highway driving is dangerous, lacking power and holding up traffic. It seems to be running very rich as the tailpipe is sooty black and we get the odor of fuel.
Have not done any real troubleshooting due to the workload but am planning the typical tuneup steps plus filters.  Further direction would be appreciated.
Thanks!
Stephen