have 2001 sienna in shop habital # 3 misfire code runs ruff falls on face on take off have tried plugs had 195000 on them changed cat convertor after testing swapped coil from 2 other cylinders misfire doesn't follow coil using bosh kt340 scanner no lean or rich codition has me pulling out my hair
I doubt the car would know a single cylinder fuel injector was not firing properly, so you would get the misfire on that cylinder, but not a lean code for the bank of cylinders.
If you have a misfire on 3, and you swap the 3 and 1 coils, and the problem remains on 3, then something unique to 3 needs to be investigated.
The definition of a misfire is that the EXPECTED WORK WAS NOT PERFORMED. When a plug fires, the crank has to get from where it is to the next place within a specified period of time -- the computer knows the speed, and the gas pedal setting, so it knows that getting from here to there should take x-amount of time. If it takes too long, then the expected work was not done, a misfire is reported.
Things that impede the expected work are a weak fuel load. There are other things that can make a misfire, but they should make a global misfire, not a unique one that affects a single cylinder. I think your next diagnostic step is to swap a fuel injector. Leave all else alone, and swap an injector and see if the problem stays or moves. You could do a compression check because a bad check on one cylinder could give you the problems you have.
In a perfect world, your car will tell you where it hurts, and there's no point in checking for a stubbed toe if the complaint is a broken arm. You need a scan tool and a list of codes that the engine is producing. ARE THE PLUGS THE RIGHT ONES? If you put in a variation on what the engine wants, then the result can be erratic operation of the engine. If the engine ran well before the plugs, and ran like crap after, then the new plugs are the problem.
Personally, I find the multi-tip plugs to be snake oil, and they cause far more problems than they cure. If your motor runs with what the factory puts in, then why would you put in something else? Back in the day, right after the wheel was first invented, one may be able to be get better performance from an engine by replacing the plugs with plugs that are a heat range hotter or colder, whatever, but in engines made today, the engineers have pretty well dialed in what the motor needs to work right, and second guessing them is usually not a good idea. You are describing what happens when the plugs are not the factory specification.
I once bought a new Chevy -- an '85 Celebrity EuroSport -- with a supposedly high output engine (the car was a pile of crap that could not get out of its own way, but that's another story). After a couple of years I decided the plugs were ready to be changed. I went to the store and got plugs out of the catalog at the parts desk and put them in. The car ran like crap. I tried everything and could not make it better. I got the car to a shop to be diagnosed, and the answer was that a C was missing from the middle of the part number. It never occurred to me to put the original plugs back in, and this would have cured the problem.
As a diagnostic step, you should try the original plugs. If this cures the trouble, then get more plugs EXACTLY like the plugs that came from the factory.
The engine does not monitor fuel pump performance, and low fuel pressure could be your problem BUT that would be a global problem, not a problem that is unique to a single cylinder.
PS Punctuation helps. Some people will read your last post and simply click-out of the conversation because they cannot/will not follow along with runon sentences that have no punctuation or visible means of determining when a thought starts and stops. Just sayin' ...
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