Idle Surging, KE24DE, '97 240SX SE Auto
 

Greetings everyone,

This is my first post, but I've been searching and reading these forums for about a week and a half. I just purchased my '97 240SX SE the Tuesday before Thanksgiving and I'm loving it. I've always been obsessed with the 240 (Even as far back as the '71-'72 Z) and now I have one.

However, the car has one problem that I've been trying to chase down. It seems to lose it's idle reference point sometimes. If the A/C is on, the idle up from that prevents it from happening, but with the A/C off several things occur:

- When shfting from P or N to a drive gear (R, D, 2, 1) the idle will surge from 200rpm to 700rpm or so and eventually stabalize around 700rpm.

- When operating in a drive gear, upon stoppping (at a red light, stop sign, etc...) the idle will dip down to 200rpm or so and then recover to 700rpm.

- If starting the vehicle while it's at or close to normal operating temperature, it may stall due to the extremely low idle. It doesn't posess these symptoms when the engine is cold. I have not had it stall while driving, only on hot start ups.

- The "Service Engine Soon" light is not on, nor has it ever come on in my week of ownership. The ECU/ECM reports code 55, indicating everything is OK. The bulb is present and does work, as it lights up when the key is in the "ON" position.

- The battery had extremely corroded terminals. I have since cleaned that and the problem still exists. (Was wondering if it could of been a +12V or GND reference problem.)

- The engine is completely stock. No modifications what so ever. The air filter is clean and unobstructed.

- The battery was disconnected for an extended time (15 minutes or so) when I cleaned the terminals, so to the best of my knowledge the ECU has been reset, and the problem persists.

- There are no obvious vacuum leaks, no major hissing, but then again, I have not looked very hard for one...possibility?

Any help you guys can provide would be much appreiciated and thanks in advance. I haven't owned a Nissan since my 200SX collection ('81, '83, '84 Turbo, and '86.) I haven't worked on a Nissan product since the CA18/20 and the NAPS-Z 2.2L found in my S110s.

I have been reading some stuff(also a total newb)
It could be the fuel pump, they seem to go out a lot

IACV intake air control valve going bad. to search for vacuum leake use a smoke machine or some propane. propane will cause engine surge when it hits the leak. smoke machine will show you the source of the leak. best of luck.

I am not inclined to suspect a fuel pump as the problem only persists when the engine is warm (at or near normal operating temperature.) I don't think the low fuel pressure of a dying fuel pump would care about operating temperature or not. I can only assume that problem would be consistent throught the temperatures.

It's also not a problem with the "idle-up" is engaged with the A/C compressor running, only with the A/C off.

I've had a few people point me in the direction to this IACV. It seems to be a "weak spot" (as in they fail often) in the KA world. I will check the valve in the upcoming week and hopefully find that it's the source of my problem. THe surging/low idle problems are really becoming quite annoying.

I read in my copy of the FSM to check the resistance across the valve and for plunger movement. Hopefully I can get up enough motivation to get to the valve (it seems buried) and do this.

S13 240s calls me master tech. How much did you pay for her?

I've had idle problems in my 95 and in my 97 maxima. Check out the IACV, EGR and TPS. Check all the connections for corrosion and try running seafoam through the IACV and EGR.

Not that it's relevent to this post, but I paid $5200 or so including TTL and financing the Tuesday before Thanksgiving in 2004. She had 63k on her at the time, and is now approaching 84k.

Yes, it's been a long time, and I have not resolved the issue because it's not that big of a problem and Nissan wants about $170 for an IACV. I'm not inclined to think it's TPS as it's a hot/cold start issue. However, EGR is a likely culprit and I will look into it. Thanks.