A few years ago I bought a complete 2.0L Type IV engine. The word from the seller was that he had bought the car for other purposes and had only driven it a few miles to get it home. He reported that the engine ran fine when cold, seemed to have very little oil smoke, but ran like crap after it got warmed up.

I shared this info with my son Mike who works as a heavy-line technician at a Dodge dealership in Scottsdale, AZ. He also has 914s (that are parked at my house in Flagstaff) and drives a 1965 VW Bug for his daily driver. He knows a bit about engines in general and knows VW engines well.

So anyway... Without experiencing what the engine is actually doing, Mike says "All it needs is a valve adjustment. The valves are too tight."

Smart kid! Sure enough. When I put the engine into a car I adjusted the valves first and they were too tight. This means that when the engine is cold the valves close fully and you get an engine that runs like it should. Once the engine warms up the valves expand and no longer close fully. This affects vacuum, which effects the FI system, which makes it look like you've got an FI problem.

I've seen this same kind of thing come up dozens of times in the garage. Almost universally the angle of attack on the poor running problem is that there must be something wrong with the fuel injection system. The poster is asking about what FI component to spend lots of $$$$ to replace to fix the problem. Often no one wants to believe that it could be as simple as a valve adjustment, but in 99% of the cases when the owner has actually done a valve adjustment they find that the valves are too tight.

So the lesson I learned is to always start with the simple, cheap, solutions first. A valve adjustment costs virtually nothing, but so much about the engine systems' functionality depends upon proper valve adjustment that it is foolish to be chasing after other possible solutions to a condition without first making sure that this is right.