'92 240sx Idles rough, bogs, lacks power

[js959]

hey everyone. well my 240 has had this problem for a little while now. cold or hot it idles rough, bogs, lacks alot of power, at any rpm in any gear, and sometimes it will have a bunch of little backfires out the exhaust when decelerating. also it is not running rich. my spark plugs are really white and have been in there for a couple or few months.

here are most of the things i've checked/replaced or are fairly new:

spark plugs
wires
cap and rotor
tested coil
checked ign. timing
walbro 255lph (about to boost real soon)
300zx fuel filter
new injectors and orings
Fuel press. reg. and oring
MAF
TPS
Eng. temp. sensor
o2 sensor
compression test
checked for vacuum leaks
checked vacuum - aprx. 20 in.
pcv valve
idle control valve
fast idle reg.
checked grounds

could it be the crank angle sensor? i'm also going to get different shims (adjust valves) soon.
Any suggestions are welcome, i need to get her running right so i can finally boost it :)

[orion::S14]

...could it be the crank angle sensor?

...i'm also going to get different shims (adjust valves) soon.


CAS - No...it would throw a code. They are typically GOOD, or BAD...not in between.

As for valve shims...why? That's a total waste of time, unless you have cams with a different base lobe circle. If you have any common (JWT, BC) aftermarket cams, or any other stock Nissan cams (i.e...248/248)...then that's not needed.

As for the problem - Try the knock sensor. Unplug it, test with a resistor (EDIT: 1,000 ohm, per "nrmskate" reply, below)...see if that helps.

Have you pulled the codes?

- Brian

[js959]

sorry i meant check the clearances, not just throw different ones in lol. i'm just throwing most the stuff i'm doing out there just in case someone notices something i missed.

yeah i checked for codes and nothing, just 55.
as for the knock sensor that's one thing i have not gotten around to check yet. i'll check it tomorrow and let ya know. thanks for the responce btw.

[nrmskate]

It's either your Timing or Knock Sensor.

Get a 1,000ohm 1 watt resistor and put it in the ECU harness that plugs into the subharness.

Should solve your problem, if not, report back with info and some meter readings.

[js959]

little update.. the only 1k resistor i could find was a 1/2 watt, and still has problems. so i'm going to try and find the correct one. also, just to see what it did i unplugged the knock sensor and ran it, but still the same.
i probably won't be able to do anymore untill tomorrow.

[js959]

ok i checked the knock sensor with an ohm meter how the fsm says to. with the car off i got about 562,000 ohms and when i tapped the sensor with a wrench it jumped. and with the car running it was about 550,000 - 555,000 ohms. but.. i don't know the specs, so can someone let me know, or let me know about a better test.

also, i tested the o2 sensor through the ecu and the light didn't blink like it's supposed to. it stays on for about 15 seconds, then goes off for about 3 seconds. then repeats over and over.

[js959]

haven't posted here in a while. still have the problem.

i replaced the knock sensor because it looked almost melted and was cracked all over, and now my car runs worse. anyone have anymore ideas? thanks.

[KiLLeR2001]

White spark plug tips usually means its running too hot, ignition timing might be too advanced. What does your exhaust smell like? How long has this been happening? Was your car running fine one day but then suddenly bad the next?

[clark]

you sure you don't have a vacuum leak?

[biggbadd240sx]

what you should do is check all the heator hoses vacuum hoses and wiring because most likely one of those is crimped, bent, or cut and your all those problems in your car.... thats usually the first thing you do before replacing anything because your spending money, later

[js959]

i've had the problem for a while now. ignition timing is set at 20* like it always has. cam timing is correct. i forgot what the exhaust smelled like.
also sounds dumb, but the fuel rail is sitting pretty shitty (stock rail). it might acually have a vacuum leak past one of the insulators, and is it possible the fuel isn't getting in the cylinder correctly??

[Spring Break '92]

My brother has about the same problem with his 'vert. No codes from the ECU. I had suggested to him that his cat may be starting to deteriorate and clog. He banged on his cat with a hammer, and the problem went away for a while. It did come back and I don't think he has been back to bang on it anymore since. Try it, what can it hurt? Tell us what happened.

[js959]

well i acually have test/delete pipe. thanks for the suggestion though.