Why does the AC cause the 1988 VW Cabriolet engine to misfire ?
When I drive my 1988 VW Cabriolet the engine runs fine (new injectors), but it will misfire as soon as I put on the AC when I am traveling at below 10 MPH or in heavy traffic. Faster speeds are OK, but the engine misfires at lower RPMs when I have the AC on.
Well, the AC compressor puts a load on the engine when engaged. On a 90-hp motor like yours, this can be substantial. The injection system is supposed to deliver more fuel to accommodate the load. If this doesn't happen, the car mar idle poorly. If the compressor is old and near failure, it may create a load above what the injection system can handle with similar results. Given the age of the car, I recommend a rebuilt compressor. If no help, your injection system is suspect.
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