car missing! need help

[Uncle T]

I bought an 89 240sx with automatic transmission for my girlfriend, immediately replaced entire exhaust (oem not performance), injectors (one was leaking pretty bad) fuel filter, plugs, plug wires, rotor, rotor cap, air filter. Car ran great now under any once in drive the car acts like it's running on 3 cylinders. It does not do it under heavy acceleration but it does do it at any speed under light acceleration, but not until you put it into drive.

I'm thinking there may be a problem with the EGR valve giving the computer bad info but I was wondering if anyone had any other ideas before I go replacing unnecassary parts.

thanks for the help

T

[navysnail]

first, before you replace anything, check it. find the cylinder that you think is missing(if it is a cylinder). check injectors, make sure connections are good, distributor is tight, timing is 15 degrees btdc, no air leaks, sensors meet factory specs, ect..., anything that has to do with anything you just replaced.- hope this helps Michael

[tds8840]

make sure you got all the plug wires on tight. I had the same problem on a truck once right after tune-up. Turns out I didn't get one of the wires on completely.

[240_2NRman]

Check your O2 sensor . even if u changed your injectors there still might be a leaky one...240 injectors are NOTORIOUS for that and check the resistence in the connectors.

[Uncle T]

Thanks guys, I should have mentioned that I changed the plug wires when the problem started since that was the only part of the tune up I hadn't done yet so I am pretty sure they are not the problem.

The injectors checked out fine but I'll be sure and keep an eye on them since they seem to have such problems (my mom's maxima is the same way)

so it's O2 sensor first, and if that is working properly?

thanks again

T

[DGA]

If you put your injectors in with out lightly oiling the O-rings there is a chance that they ripped. This exact same thing happened to me. The car is fine while its accelerating, but at idle it feels like crap. I also talked to some Nissan techs at the dealership, and they told me the same thing. It will take a very small rip for the gas to start rushing past the injector into the cylinder at 40 psi.

[ginostef]

If you're having and idle problem, then most likely it is a mixture or ignition problem. You can check the ignition quick, and sounds like you have already ruled out the plugs and wires. Just to be safe, I would pull the plugs one at a time to be sure they all look the same. One may be wet, or "cold" - that's a good sign the ignition ain't working like you want on that cylinder. A real rich lope will develop with leaky injectors, but that's rare - more likely you may have developed a vacuum failure someplace. Try the plug pull to isolate the problem if you can, if that doesn't do it, then put a vacuum gauge on it and see if it is bouncing all over the place on you. Next thing to try is reset the ECU - pull the battery connection and let it sit for 10 min or more, then rehook and start it. My guess is there is a failure in the idle circuit - look at the connections to, and the operation of the IAA, and IACV. Good luck!

[Chingon]

check plugs.