Thread: Idle Issues

Hello everyone,

Here is my setup:
Car: B15 SE
ECU: B14 JWT
Harness: B15 w/B14 ECU connector conversion

This setup has been running great and idling smoothly all summer long. However, now, with the cold, I've just started using the defrost functions on the car. FYI, the AC is wired everywhere, except for the compressor relay, because I have lost the connector and the system is empty anyhow.

Now, whenever I turn the rear and/or front defroster on, the idle remains fine, so everything looks good. However, when I turn them back off, it looks like the ECU is not aware that they were taken out, and keeps on compensating. This means that the warm idle rises to 1500-2000 until I randomly play around with the environmental controls or restart the car with everything off.

I tried disconnecting the A/C idle valve on the TB, but this worsened the situation (the idle was always wrong). Should I keep it disconnected for the time being (until it works) and readjust the idle?

It's not a huge issue, but it can get irritating. Has anyone else run into this issue?

That guy naddie is having idle issues as well. He posted them up a week or so ago back on b15sentra.

My car idles at 750-800rpms, a/c completely gone tho, connectors are just hanging around.

Hey, glad you made it to the "dash" forum

Are you still using the B15 IACV?

Cool, thanks!

Yep, using the complete B15 TB. Not using the VE sensors.

maybe a good tb cleaning? see if anything results from it?

The throttle body was taken off and fully cleaned when I got the motor in (during the summer), but thanks for the idea.

The TPS value does not really change on the AFC Neo's display when this happens, so I'm fairly certain that the TB is not the culprit here.

Are you sure turning the rear defroster on activates the A/C?

So the way your wiring is setup now, does the compressor actually kick on if you turn the front defroster on?

I was going to suggest disabling the switch on the HVAC controls that turns the A/C on when you set it to front defrost. If you take the HVAC control panel off you will see the switch behind the vent selector (behind the first defrost position). The way the factory A/C is setup is that even after you have switched the front defrost off, the compressor is still running.

Since your system is partially wired, and non-functional it shouldn't hurt to try this.

^^
Actually, I'm sorry if I was unclear. The rear defroster is not starting the AC by any means.

I will try out what you just proposed over the weekend. It may help resolve my issue.

Thanks

I haven't had a chance to work on the car for a while now, but I'm still getting the above-mentioned issues, and have not disabled the AC functions on defrost yet. The thing is, I may still get the AC system filled, so I will want these functions back for sure when I get it working.

However, I did notice something lately. Whenever something that uses AC is turned on, both radiator fans start up, no matter the coolant temp. I have wired everything almost exacltly as mentioned on the JGY site, and I did notice this:

Pins 13 and 14 (B14 ECU side) are connected to 12 (B15 high fan relay side).

On a B14, according to the FSM, the high fan relay is pin #13 and the low fan relay is pin #14. On a B15, they are respectively pins #12 and #13.

So, instead of having (B14 to B15; according to the JGY conversion):
13 and 14 to 12

I could wire:
13 to 12
14 to 13

As it is now, when the car is idling and I turn the AC-using functions off, the engine almost dies, then comes back to the "too high" idle. Perhaps there is more of an electrical load than the ECU is expecting, and readings get screwed up? Perhaps the ECU gets a current return through the high fan wire when the low fan wire is turned on? Anyway, I'll try to correct this when I have the chance. Worst case is, it doesn't fix the idle problem, but I get the fans back to their "two stage" functionality.

I'm pretty sure the fans are supposed to come on when anything using the A/C is turned on. It's probably to move air across the condenser which is in front of the radiator.

Disabling the "Auto A/C on" switch when to switch to front defrost is not a big deal. If you do that all you have to do is remember to turn the A/C on manually when you want to defrost. Your other option is to cut the wire that is going to the "Auto A/C on" switch. This is easily reversible with some solder if you need to.

I can't say I can offer too much more insight into the other issues.