The powertrain control module (PCM), which controls virtually every function of the engine and automatic transmission, depends upon an input signal from the TPS (among other things) to calculate fuel delivery and ignition timing strategy.
Sometimes even the simplest items will cause a drivability problem. Then is this situation where the issue is both intermittent and includes a very short window in the production run. The combination of these factors can cause frustration for the technician, but thankfully this tip will help to reduce the frustration level.
Engines have become very reliable in recent years, many reaching over 200,000 miles without major issues. As technicians, we replace a lot more ignition coils than timing chains.