1993 Nissan 240SX-no power '>1/8th throttle'

[Schrute Farms]

My 240 will stumble and lose power if I give it anything other than maybe 1/8th throttle. Sometimes it will hesitate and then I'll have power but it still feels like it's not pumping out all of it's horsepower/torque.

All emissions have been deleted (EGR, etc.)

I did the vaccum leak test per the FSM (pinch the blowby lines coming off the intake tube) and the RPM's didn't rise, they fell by about 200-300.

[Schrute Farms]

Oh and I forgot to mention- there are no check engine lights. I'm lost! HELP!

[aris_unlimited]

It seems to me like deleting all of your emissions components could very well have caused this. Meaning that it could be any number of things emissions related. If you still have the stuff I would suggest putting it back.

[Schrute Farms]

I do not have any of the emissions stuff as it was deleted by the previous owner.

The car is N/A and has a three inch complete exhaust and a header. I was thinking that maybe this could be the cause? Should I have all my piping changed to like 2 inch?

[aris_unlimited]

Well a 3 inch exhaust is definitely too big for an n/a 4 cylinder. I would suggest reducing it to a minimum of 2.5 inches. Also I assume you have the catalytic convertor deleted as well? This will also remove some of the back pressure that the car needs to have.

[Schrute Farms]

Well a 3 inch exhaust is definitely too big for an n/a 4 cylinder. I would suggest reducing it to a minimum of 2.5 inches. Also I assume you have the catalytic convertor deleted as well? This will also remove some of the back pressure that the car needs to have.

You are correct sir. The catalytic converter is deleted. Gotta love no emissions testing in MI. I will cut the 3 inch piping out and weld a reducer on my exhaust and then change it to 2 inches or something like that. I also forgot to add that I'm only getting like 19 MPG in the city. Would my 3 inch exhaust be causing bad gas mileage in addition to crappy performance?

[carmo]

I don't think the exhaust has anything to do with the drivability. Of course that's not to say that the exhaust may be a little too big. I don't know the pros and cons of more of less back pressure. I always heard no back pressure can cause valves to get burnt. Maybe that already happened. A compression check should tell you something. Sound to me like a sensor issue. With the key in the on position does the check engine light ever come on. Thats bulb check, and if the MIL never comes on then it's been disabled somehow. Start there and also trace down the harness and check your major sensor wires. MAF, coolant temp., crank sensor, etc. Also get a look at the ECM. Who knows what the previous owner may have done there.

[Schrute Farms]

Update- I put the stock intake back on with a different MAF sensor and the car actually seems to be running a lot better. I'm thinking the MAF was the culprit. I only drove it down the street so we'll see tomorrow when I drive it to work. I now have another problem though that I'm going to make a new thread about.

[Schrute Farms]

Update 2- Car is still fawked. I jumped the gun. Now it only has the problem after driving for about 8 miles. Definitely not the o2 sensor because that was just replaced. Now it loses ALL power and I can barely get out of my own way. It's dangerous. I'm suspecting the fuel pump and/or FPR is on it's way out so I'm going to drive it about 15 miles and check the fuel pressure and will report my findings.
Modified by Schrute Farms at 2:35 PM 9/27/2008

[Schrute Farms]

Damn. Fuel pressure is fine. It was at 36 at idle and 43 when priming. So that rules out the fuel pump. What else should I check? Vaccum lines? I did notice an actuator in the back of the intake manifold was disconnected and a vaccum line in the vicinity of the mystery actuator was blocked off. What is this? Secondaries or something? Should I hook it back up?
Modified by Schrute Farms at 8:04 AM 9/28/2008