Weird idle and possible overheating?
 

I have an 89 240SX with about 148K on it. I had an issue with the exhaust manifold gasket for the rear 2 cylinders breaking causing an exhaust leak that affected the car to the point that it would only stay running for roughly 2 minutes.

I have replaced the gaskets and the water pump because I needed one. The car is now kind of pulsing when driving. It is very slight and hard to describe but it feels as if it has mini surges in power fallowed by slight laps in power. It does not die at all while driving although occasionally shift hard (automatic : / ) But anyhow it drives fine just you can notice seemingly wave like power and also a slight whistle like noise, similar to a turbo but not as pronounced. My car carries the stock engine so no turbos sadly.

Now the next thing is when I am done driving the car and go to park it all is well until I put the car into neutral or park. The idle then floats between 700 down to 200 RPM till it eventually kills itself... If I put it into any gear reverse drive 1st 2nd it doesn't matter the idle quickly returns to its normal roughly 800 RPM range, disengaging the gear reengages the problem...

To further stupify the water seems to be hot but the gauge never reads above the normal heat leave and the engine block itself while uncomfortable to touch for extended amounts of time is far from abnormally high...

Any help in this situation would be greatly appreciated, Im going to try and get video uploaded to show idle and possible the whistle noise if I can, but until then any ideas based on this description?

A few Ideas I was given and my current answers to them:

Several possibilities:
- Vacuum leak in intake system.
I thought that too but cant seem to find any with the usual method of checking

- Bad O2 sensor.
This is possible the wire to the O2 sensor is pretty much shot Im going to replace it tomorrow any special instructions? Its from the harness to the connector that it got britle and is cracked several places. I was just gonna cut it and solder in new wire.

- Sticking EGR valve.
Details? Not to up to par with this block I have worked on VG30's my entire mechanical history and EGR's on those didn't cause to many issues although they were a pain to get to.

- Dirty fuel filter.
Brand new

- Dirty air filter.
Brand new

- Fouled spark plugs.
Gonna pull them out and look but they wern't an issue less then a week ago dont they normally degrade slowly? Not one day they are ok the next day they are shot?

Thanks for your input Im trying to straighten this out because aside from the slight plusing while driving and whistle the car seems problem free until I go to park then I get this odd idle.

Going to have a friend look at it tomorrow bhopefully he knows hes delt with primarilly 240's although his expirance is on swaped SR20's...

Most 240's have an idle problem...take off the IACV and clean it out, clean the throttle body, and reset the computer (unplug battery and touch the negative to the positive to discharge the capicitors). The whistle is either an air leak or an exhaust leak...did you make sure you weren't leaking on the exhaust once you did the gasket? If the gauge is reading normal for water temp, and you don't feel unusually hot parts anywhere, it probably isn't overheating...does the electric fan kick on and are both the upper and lower hoses approx. the same temperature (they will vary but upper should be hot lower should be warm, neither of them ice cold).

The surging could also be linked to an air or exhaust leak near the manifold causing abnormal flow. Best bet is to fix the idle and look for the leak, then see if it goes away.

Yea sounds like a possible O2 sensor. Or like Preston said a gasket could be going out. Since you checked the easy fixes already time to start losing money haha. Start with what looks in the worst shape and start replacing. Good luck and post that video soon. Oh just popped into my head pulsing could be an injector ready to go or a bad wire in the harness. I had a stray cat try and chew through my harness one time caused a real bad pulsing problem haha.

Don't start dumping money guessing. Good idea about the injector completely forgot about those lol. But seriously I would keep looking for things before I just went spending money hoping whatever I replaced fixes it.

Wel guys thanks for all the help turned out just to be the crummy O2 wire soldered in a new one and I now have "the best idling stock Nissan 240SX" my friend Damion ever heard lol. Funny how the little things work.

As for the other stuff still gotta find the whistle, the pulsing went away with the O2 wire, and it deffinatly isn't over heating so I guess I got off easy.

Any of you guess know what a RaceOne or RaceOn (not sure which it is) wide body kit looks like and could provide me with some pic links?

Thanks in advance