Car boggs down while running

[Graphfixz]

I have a 91 Nissan 240sx and I have been having an issue for about 3 weeks now. As I am driving around town or the highway, the car feels like it looses all power, bogs down, looses spped and then suddenly comes back to normal. Sometimes, a very few times, it doesn't come back up. I have to leave it and come back to it.

This happens at all speeds and although it is happening more frequently it does not happen every day. I have:

- cleaned the MAF
- changed the heat sensor
- new oil, filter, fuel filter

Codes are not showing up. I keep getting 55.

any help will be greatly appreciated.

[Graphfixz]

could it be the transmission?

[Timothy S]

You've looked at this as a fuel problem so far, but could it be tied to a fuel pump or the relay that controls it? What about spark plugs wires and distributor connectors? a loose spark plug wire might cause one cylinder to come and go creating a loss of power and setting a misfire code.