1991 240sx, Excessive power Loss in a KA24DE. Stumped.

[unlearning]

Ok, so first to try and explain what is actually happening:

When starting a roll in a low speed/gear situation (from a stop, or a slow roll) generally at about 2kish-3kish RPMs basically all power drops off. Press on the gas and the car continues to rev but revs extremely slow (ie not a slipping clutch) Till you hit just over 3k RPMs, Generally.

Happens to be more pronounced in 2nd gear than anything. When pulling in 2nd happens about 80% of the time. Sometimes in 3rd and 4th, but much less often. The Power curve through 7k RPMs has greatly diminished in the past few weeks since it started acting up. I'm not able to put my head back into my seat like I normally should.

Also in higher RPMs in 4th and 5th on the freeway you can feel a little "sputter" every so often. Not at all like the engine is dying, just losing power.

Compression on all cylinders is a solid 162~ Warm, 140~ Cold. Fuel PSI is a solid 32-34, through idle and WOT (struck me as slightly odd). Distributer looks fine, and plugs are getting solid spark. Just removed AIV this afternoon and the power loss seems even more pronounced now.

Getting frustrated not being able to tell what the deal is. My only instincts at this point are saying Fuel Pump going out, Injectors Clogged, or Air leak in Intake, Sticky valves, or transmission/differential crapping out. To put it nicely I'm stumped, no idea.

Modifications: ACT 6puck Unsprung with Fidanza Lightened Flywheel.Suspension with Rear and Front Wheels.AIV removed.Cat removed.

--Not much

Anyone have a similar issue?

[4cefed]

Few things to check.

Try unplugging MAFS, this happened tome in a different car, but same symptoms.

Switch in a different coil.

Make sure plug wires are in good shape. Consider checking at night or in dark garage to see sparking.

Make sure there is no oil building up in the spark plug wells.

Change fuel filter.

Spark plugs are gapped correctly, right?

Could be fuel pump, but try cheaper things first. I'm sure there are more things to check, but this is all I can think of for now.

[DubsSuck]

double check distributer timing

[PapaSmurf2k3]

if you say its 80% of the time... meaning intermittant... then its probably an electrical issue.

I have pretty much the same problem on my 91 KA-T... only its like 99% of the time there is little to no power.... but when the planets align and everything clicks... holy s*** you better be holding on to something.

I'm about a ball hair away from replacing my entire engine room harness... issues like this just piss me off.

[maryjane]

mess with your timing, we just eliminated his air box, cat and egr system and it ran like crap till i adjusted the distrib then it ran and pulled like a champ

[rva240]

i know this is an old thread, but did you ever figure out what it was? my problem sounds identical

[Mercury_Hg]

Could it be the knock sensor causing the ECU to change maps? I don't know exactly how that'd behave.