Wierd Idle

[silvios]

Hey everyone

I have a question about cold start and idle.

When i start my CA on cold start, the idle drops and struggles around 450rpm...
I give her a blip of the throttle then she steady's around 1000rpm.
This is the cold start.

Randomly while i am driving, the idle will go upto 1500rpm, when warm?

I find this rather odd behaviour but i am curious what it could be.

It could be linked to IACV, air regulator and TPS?

Any advice would be great!

[float_6969]

Read through the FSM about what the idle should be, but I will tell you that as far as the poor startup idle is concerned, the air regulator under the throttle body is bad and needs replaced. It's common for it to fail, usually stuck shut, so it doesn't idle up. The same valve is used on the SR20 B13 Sentra's. There are 2 different ones, one for manual, one for automatic. I used the manual one, and the idle isn't high enough, BUT, I have high compression, and I'm running E85, and the oil I was using was probably too thick for the temperatures at the time. I didn't get a chance to see how it behaved during the summer as the engine had to be rebuilt due to a failed oil filter.

Because I need to replace it with an automatic version, I would be more than happy to sell you mine. It has maybe 15hours on it.

As for the random 1500rpm jump, the IACV may be sticking. You might try running some seafoam through it and see if it free's it up. I'd replace the air regulator first though.

[sjbsuperman1425]

hey Ryan,

exactly what year sentra is that? Also, why are you using an automatic instead of a manual? my car still idles funny from time to time but I'm replacing the air regulator and IACV to be safe. The IACV is the 88 Pulsar NX SE correct?

[leadpaw]

The air regulator for the Kn13 1988-1989 pulsar will not work they had a different intake manifold and in turn different air regulator. Instead of having a 2 pipe connections it had one pipe connection and a flange that bolted to the intake manifold. The Iacv/aac also probably wont work(without modification) from the pulsar because the pipe coming out of the iacv/aac valve doesnt have the 90degree angle to clear the head and valve cover. You will need an air regulator from 1991-1994 sentra SE-R with a SR20DE.

Yeah cleaning out the iacv/aac may help. just remove it and clean it with some brake cleaner and a brush.

[Shagi]

Silvios,
I have the exact same problem with my CA. It happens more when I have the air-con on.
I deleted the cold start air regulator along time ago. I also swapped out the FICD and AAC valves the other day. Still does it.
I am going to check the wiring next.

I am very keen to hear of any progress you make and I hope my info helps.

[float_6969]

hey Ryan,

exactly what year sentra is that? Also, why are you using an automatic instead of a manual? my car still idles funny from time to time but I'm replacing the air regulator and IACV to be safe. The IACV is the 88 Pulsar NX SE correct?

I'm running the manual one now, but it doesn't seem to give me enough revs to keep the engine idling well. I think the automatic one will fix my issues. If it doesn't, I can add another idle valve with my standalone and do it that way, but that will be last resort.

The air regulator for the Kn13 1988-1989 pulsar will not work they had a different intake manifold and in turn different air regulator. Instead of having a 2 pipe connections it had one pipe connection and a flange that bolted to the intake manifold. The Iacv/aac also probably wont work(without modification) from the pulsar because the pipe coming out of the iacv/aac valve doesnt have the 90degree angle to clear the head and valve cover. You will need an air regulator from 1991-1994 sentra SE-R with a SR20DE.

Yeah cleaning out the iacv/aac may help. just remove it and clean it with some brake cleaner and a brush.

All of this is right^

[silvios]

Ok i know where the air regulator is - but can u clean it?

With the IACV - if i think it is what i found, it is in a b**** of a spot to unscrew and clean...
I cant unscrew the bottom screw because of this bracket that is in the way.

What i might do is diconnct the air reg? on a cold startup and see if a difference is made?

Ill post if i have any news.

[leadpaw]

Disconnecting the air regulator would not help anything. The air regulator is given constant 12v power once the engine is started to close its inner valve and drop idle at warm up. Disconnecting it doesnt change anything at cold start up except possibly leaving it open when the engine is warm and keeping idle high (if its working properly).

[float_6969]

I've NEVER cleaned the air regulator and had it fix anything. One time I did it and it went from never idling up, to never idling down. It's not an expensive part, maybe $50-$75. Just replace it. It'll probably work longer than you'll have the car for.

[Shagi]

So i pulled apart the Auxiliary Air Control (A.A.C) and cleaned it, then sprayed the slider with INOX.
Problem immediately gone.
Drove to the shops with air con cranked. And idled down beautifully.

[float_6969]

Glad you got it fixed!