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If your sure everything was good you have checked then I suspect you have an issue with backpressure from a clogged catalytic convertor. I would have a backpressure test done or for a quick test you can do now pull the O2 sensor out from in front of the catalytic convertor if this makes any improvement than you know the cat is bad and will need to be replaced.

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Ok than it has to be the timing. Must be a notch off you will need to have the timing fixed in order to have it working like it should. Had one of these just the other day.

Yes what happens is the tensioners inside will get worn off and can cause it to get out of time causing the exact problem your having word for word. Just was hoping it was more simple but its not. Thanks

Danny

Most of the time they never make noise they just cause the timing to be off when they get worn out. If your fuel spark and air is good which you have indicated then its the cause because you need all of these to be inline in order to run the car properly.

Danny

It will come and go when the tensioners get worn out if your sure everything else is good then I assure you there is a problem here. What will happen is it will just not keep enough tension on the chain but will not make any noise in turn it will cause the vehicle to not have any power at all. I diagnosed this same issue recently it was very difficult because of the symptoms but since I have experienced it now its very simple to see.

Danny

I would do a leak down test you can set the engine at TDC then check cylinder 1 if the timing is off it will have leaking in the cylinder but if the tensoner is worn and only happening when running it will be difficult but its the first thing I would do. Thats what I do everytime to make sure.

Danny