NISTECH, bad idle in sohc 240sx, help.

[Altiman94]

My idle goes from around 800 rpms all the way up to about 1800 rpms. It is inconsistant within that region, never idling stable. I replaced the water temp sensor and that didn't help, also the ecu. What could it be? and how do i check it?

[NISTECH]

is it rapid fluctuation? IF so I would say hurrendous vaccum leak like the brake booster hose or the pcv hose under the intake. also if you aiv is still in it try pinching off the the hose for it. although I assume you already removed it since it seems to be the thing to do.

[Altiman94]

no aiv, checked for vacuum leaks. It is semi-rapid. Once in a while itll sit around 800 or 1000 but it always seems to fluctuate eventually.

[NISTECH]

didnt you do something with your coolant temp sensor. That would be the next thing to check. is if it has a good connection between the sensor and the harness. no corrosion or loose terminals.

[Altiman94]

I did replace that. There was no corrosition, but the connector doesn't snap in plac eon the sensor. It never did on the original one either. It helped a litte when I put the new sensor in, but that clip didn't snap on there. Its connected, but not snapped into place if you know what I mean. Could be a bad connection there I guess. Could that cause my idle problem?

[NISTECH]

yes cause its in and out of thinking it is cold. so it does the cold enrichment when the coolant temp is below a certain temp. This will make it run richer and open the cold air valve a bit. you could also have a problem with the harness along the valve cover try wiggling that and see if it respondes to movement of that harness.

[Altiman94]

I was thinking that the loose connector was part of the problem, so I'm gonna have to look at it again when I get it back from the shop. I've had so many problems with it ever since I had that rebuilt motor put in. Hopefully after I get this figured out it'll be good.

[NISTECH]

make sure you tighten the female pins in the connector with a scribe or something pointed.

[Altiman94]

which sensor is for the ecu. I replaced the larger one.

[NISTECH]

the 2 wire sensor is for the ecu. probably a red or yellow connector

[Altiman94]

I think the one I replaced was the one wire sensor.

[Altiman94]

do you have a part number for the correct sensor?

[NISTECH]

no they vary between models. I cant remember them all..lol

[Altiman94]

ok. I replaced the one closest to the valve cover. That's the one they gave me at Advanced Auto. Is that the right one?

[NISTECH]

I am not sure about the orientation of the 2. but you have 1 sensor with 1 wire with a black connector usually with a rubber boot over it. and another with 2 wires plastic connector with a metal clip on it. which one did you replace?

[Altiman94]

it was a plastic orangish colored connector

[NISTECH]

that was the ecu's coolant temp sensor.

[Altiman94]

alright, that's also the connector that doesn't snap onto the sensor itself. It seemed like it really helped when i first got it in. Was pegged at 800 rpm like a rock. SInce then, it's not soo good, sometimes its right on, sometimes not. I think it may be becasue the connector doesnt snap on makign the signal intermittant. I don't have my 240 back to check it out though.

[96sx]

had the same prob. mine is still crazy and I have since changed the sensor and the entire connector... I don't know what it could be.

[bustav13t]

i'm somewhat having the same problem, and i wanna check too, so where would i find the coolant temp sensor?

[NISTECH]

front of the intake manifold near the water inlet.