On re-start after shopping, shudders, dies within 20 sec.

[pinetreeporsche]

Ten days ago, this started-- yes the weather was very cold, but it continues in the warmer spells: When I've been driving long enough to warm it up, then stop to shop, when I start it again it starts normally, but drops into a sputter/ cough at very low revs. Fluttering the gas pedal does nothing to help- the first time it happened I was moving into traffic; luckily I had the option of delaying the move forward, which could have been bad, indeed. When it died, a restart had it back to running normally. After a few times, I started experimenting: seems if I kill the key when the rev-drop begins, wait a couple of seconds, and hit the starter again, it is indeed back to normal running. I mostly do this now before even thinking about moving the car till I've done the full dance and it's running fine. If I pull in at home (no garage) or for a long appointment and come back hours later, or the next morning, it starts and runs fine.
SO- any ideas on what's going on? It seems like a running-out-of-gas sutter, so I wonder if something lets air into the fuel pump line causing starvation. Why would it then start normally and run fine with the re-start? And btw, no fuel drips showing up under the fuel pump, or anywhere else, and no gas smell. The winning contestant gets generous praise. -Chris

[MarkWard]

What year vanagon? Stock engine? If it's a digifant system, I'd be checking the coolant temp sensor and circuit.
_________________
☮️

[pinetreeporsche]

Sorry- Stock '87, except for the bigger jugs and pistons when rebuilt some years ago. Stock F I, for sure. But re: the temp sensor: the motor/coolant are the same temp for the second effort, 20 seconds later than the first time-- if that means anything.

[MarkWard]

Engine coolant temp sensor is different than gauge temp sensor. You need to measure the coolant temp resistance with an ohm meter and compare against graph in the factory manual. That is only a guess.
_________________
☮️

[djkeev]

When you send a surge of electricity through a connection, ground or hot, it almost always bridges the "gap" and connects.

If the connections are dirty or loose, the "gap" isn't bridged.
If you turn it off and try again, it will often "bridge" the gap.

I'd start with your ground wires. Left head and body.......

Dave
_________________
Stop Dead Photo Links how to post photos

Ghia
http://www.thesamba.com/vw/forum/viewtopic.php?t=392473

Vanagon
http://www.thesamba.com/vw/forum/viewtopic.php?p=6315537#6315537

Beetle
https://www.thesamba.com/vw/forum/viewtopic.php?t=482968&highlight=74+super+vert

[DigiMatrix]

I had a similar problem with my Passat G60 syncro wagon that runs on a similar Digifant ECU.

I would do the following: disconnect the O2 sensor and see if the problem goes away. If it does, I would chase the O2 circuit from O2 sensor to ECU, looking for poor connections. The signal from the O2 sensor is very low voltage and if a connection is poor, it will fool the ECU and it will compensate by over fueling. In my case, I had added an aftermarket O2 guage which was causing the issue. I chased the problem for a very long time and got mad one day and disconnected it and the problem was gone. Car still was getting horible gas mileage, but that turned out to be poor connections to ECU from O2 sensor.

Hope it helps

[Wildthings]

Anything the throws the amount of O2 in the exhaust off will cause this, there doesn't have to be anything wrong with the O2 sensor, but there could be. What is happening is the engine seems to run fine until the ECU goes into closed loop at which point the problem manifests itself.

- Grounded coax shield on the O2 sensor wire
- Anything causing an overly rich condition
- Anything causing an overly lean condition
- Anything causing a misfire, like a bad plug or plug wire

Going through the complete diagnostic procedures in the manual doesn't take long and should point you in the direction of what it wrong.