Originally Posted by Nabby
She said she had recently had a new timing belt put on, I asked about the spark plug wires and she's sure they're on in the right order. Is compression testing still my next course, or is there possibly a timing issue, or something else?
A compression test will give you at least an indication if the timing was done correctly or if the timing belt tensioner has perhaps loosened and the timing belt has jumped.
Cofirming the plug wire sequence should be easy enough; they are marked at the coil "posts" and the cylinders are numbered one to four left to right (facing car) from the crank pulley end.
Is it the same mechanic who wants to replace the PCM that did the timing belt? If so, I would re-do all his previous work. No competent mechanic suggests a PCM replacement "to see if it helps" as mikebontoft has already stated.