Hi all. Got a problem that started suddenly. 81 Scirocco starts and runs fine so long as engine compartment is cool. Warm things up, either by running or by sun on the hood (or on the engine with hood up) and the engine will suddenly seem like it's running on one cylinder..."chug..chug..chug..", jerking like crazy. Doesn't seem to make much difference how far the gas pedal is down. Sometimes it will catch and run smoothly for a short distance, then the problem starts again. And sometimes the engine will just die.
Not useful to only be able to drive 2 miles in the morning. Does anyone have a clue what could be wrong?
Thanks very much to all who replied. I should have noted that vacuum hoses, boots, plugs/wires, dist cap/rotor, FI O-rings, O2 sensor, and air filter were all replaced recently. Exhaust, even with engine chugging, looked clean. Note that when the engine went into chug mode, the tach bounced down on zero.
At some point in the past I had re-connected a broken wire in the connector to the distributor. But I had not considered the hall sensor, and don't really know how to test it.
This morning the engine started and warmed thoroughly without issue. But I didn't drive the car immediately. I shut down and removed the connector to the distributor. The contacts looked a bit corroded. Not having a tiny file to go after them with, I inserted/removed the connector repeatedly to try and ensure contact. I then removed the distributor cap and removed a bit of oil film from what I think is the hall sensor with a piece of paper. Then I drove the car.
At first all seemed well, but then the problem returned. Not not as bad before, though. I was able to limp into the driveway. With engine still chugging, I lifted the hood. After a few moments the engine started running smoothly again.
Again I removed/inserted the connector a few times and the engine started right up. I let it run for a while with hood down, then drove around the block. No problem.
It remains to be seen if this problem is really fixed. But unless there's a lot of coincidence going on here, it seems to be related to the sensor and/or the connector.
I'm going to have to keep digging. The car sat in the sun for a few hours this afternoon and the problem returned.
I had another heat-related problem a few years ago. The starter would not turn when the motor was hot. Mechanic could not find the problem, but I did: the wire to the solenoid had cracked insulation and the wire inside was corroded. I ran 12 gauge wire from the firewall to the solenoid and all was well.
I've had a similar problem, which may not have any relation to your problem, but is an easy check. The symptoms were identical and random. Check the group of ground wires that attach to the head using a rear valve cover bolt as the mounting point (drivers side). Pull gently on each wire to see if any are broke. They usually break when the front motor mount goes bad and allows the engine to move more than it should and strain the wires. Easy fix too.
I've not been able to find the culprit. I've only got a couple of weeks before escrow closes and cannot deal with this issue. If anyone here knows anyone in the Los Angeles area who wants an 81 Scirocco S w/
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