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I'd appreciate some help on this one. I've been investigating a 1993 Nissan Maxima (3.0, 6-cyl, less than 100 000 miles on it) which occasionally runs only with five cylinders. Here are the facts:
When the car runs normally with six, it's not jerky, it accelerates normally, just like it should. When it runs with five, the five cyls seem to work ok but the failing one doesn't work at all, it misses on every round.
Based on exhaust diagnostics, the carbon hydride level is ok but oxygen is bit high so obviously the problem is that the one cylinder does not get gas. The plug gives spark ok.
I'm pretty baffled with this one. Electrical problem? Faulty fuel injector? Or what? I've asked a couple of shops whether they could do something to it but none of them seem to have a clue about the problem. They said that they could start by replacing the fuel injector but with bad luck that would just be an expensive job with no help. Thus I'd appreciate on your help if you have encountered such a problem or could give me any diagnostic hints. Below are some of my observations about the problem. However, as the problem is occasional, it's pretty difficult to say whether these observations are worth anything...
After cold start, the car sometimes runs with six, sometimes with five. There might be some connection with stopping to traffic lights and accelerating and losing the one cylinder as quite often during the acceleration the problematic cylinder starts missing. On the other hand, after losing the cylinder it might suddenly come back a couple of seconds later. But it can miss for dozens of miles in a row. If the engine is stopped when it runs on five and immediately started again the problem seens to persist. But if the engine is on stop for a couple of minutes and it's then started again, it might very well run with six.
Gas additives which should clean the fuel injectors have not helped.
What I'm wondering:
If the fuel injector is faulty, why the car sometimes works ok for dozens of miles? Can it just lock closed somehow and then, suddenly, after some shock (a bump on the road for example) open up and start working ok? How does the fuel injector work after all? What causes the fuel injector to inject fuel, some signal from "the box" or is it purely mechanical? If the injector uses electricity to open, could "the box" be broken this way?
Please, any help is appreciated. The car is in great shape except for this and has probably a hundred thousand more miles on road left :)
Br,
Mika