Quote:
Originally Posted by glatt
Oh, yeah. There was more resistance blowing through the old filter, but it wasn't dramatic.
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So a new fuel filter did not solve anything. An original and still 'wet with fuel' filter might explain a slight restriction. It would not explain fuel restrictions during idle.
Imagine what happens when the car was actually demanding much fuel. Idle demands little. Heavy acceleration requires plenty of fuel. The engine would obviously stumble and almost stall on acceleration if that filter had any relevant obstruction (was dirty).
An intermittent problem can be created by many things that exist constantly. For example, if a fuel pump pressure was slightly low, then the car would work normally almost all the time; only have intermittent stumbling.
The EGR valve would not move smoothly. But the car would work normally almost every time - just not in the rare time when the EGR valve intermittently stuck. Move the valve by hand to feel the restriction that only rarely gets stuck. Unfortunately intermittents not reported by the computer can be this difficult to locate.
Distributor vacuum advance and retard motion can also be intermittent. In one case, I discovered that intermittent was created by grease on those moving parts that had become sticky with age. It always existed. And was located by physically moving the part by hand. The sticky grease always existed. But the resulting bad performance only occurred rarely and without any one common action making it happen. Intermittents are that nasty to find when computer diagnostics do not report them.
As you recall, shop manual provides a list of suspects that are numerous.
BTW, the engine is almost two completely different engines when in idle and when moving the car. Many parts do completely different operations in those two modes. Another way to eliminate suspects from that list. That was the case in cloud's IAV failure. Only the 'idle' engine was failing. The 'moving the car' engine worked just fine.