**** Need Help to diagnose Crazy High Idle Speed on Nissan Sentra ****

[Yu Chi Yip]

***** Need help to diagnose Crazy High Idle Speed..*****

It is a Nissan Sentra, E16 engine, 4 cylinder 1.6 Liter with 5 speed m/t.

Serveral weeks ago, I cleaned the engine block with the commercial soap
spray; the one I get from auto parts store here at Chicago; Trek Auto.

The way I cleaned it was that:
After wrapping the distributor with plastic bag, I have the engine warm up
and while it was still running, I sprayed the soap on the engine block.
Then, after about 5 minutes, I used water to flush the engine block,
all over the hood,

while the engine was still running.

Everything seemed fine right after the cleaning and I drove it home from
my friend's garage.

Next morning, when I started it and the Idle speed went crazy high, about
3500 rpm ( the normal one is around 1500-2000 rpm and drop to 800 in about
5-10 minutes) and did not come down even after I drove it for 50 miles.
Then I realized it was something wrong with it due to the cleaning engine
block.

My first question is: What will be the cause of this high idle speed?

After studing the service manual (from Nissan, the one cost 40 dollars),
I suspected that the vacuum control modulator (located in the right side the
the hood) was not functioned correctly, so I disconnected the electrical
wire from it (according to the manual the wire is connected to the ECC
computer under the driver car seat) and the idle speed went down to normal.
I did this right after I drove it for 50 miles. I also observed that if
I then connect the wire back, the engine speed went crazy high again. So
I left it disconnected for serveral weeks until now. I thought I had fixed
the problem. But, then the problem came. I could not get the car at high
idle speed when the engine was cold. That resulted in a annonying situation:

It stalled from time to time when it just started, even
when the engine was sufficiently warmed.

I learned that from the manual the fast idle speed (which is operated when
the engine is cold) is control by the Idle Speed Actuator which is
connected to, among other things, atmospheric pressure. That means the
Idle Speed Actuator is connected to open air (The manual also confirms that).
It is the atmospheric pressure that makes me suspect that:

While I was cleaning the engine block, water was sucked into the
Idle Speed Actuator through the air filter and messed it up.

My second question is: How can one check out if the Idle Speed Actuator
good or not? and
My third question is: How easy or difficult one can replace the Idle Speed
Actuator?

Thanx in advance to any helpful hints!!

Yu Chi Yip.

[zekea...@gmail.com]

My car starts normally but when I drive it just goes into high idle sometime but when in gear and I pull cluch out it goes down but when I take out of gear it goes to 20000 rpm

[The Real Bev]

How old is the car?

My 88 Caddy (with only 70K miles on the odo) did something like that
every once in a while. Worn throttle assembly where the rod goes
through the somethingorother. No idea why it would accelerate by
itself, but that's what I was told. Brake hard, shift to N, turn off
the engine, start up again and everything is normal. Requires a bit of
adrenaline if it happens on the freeway (every single time), of course.
It finally gave up trying to kill me and now just sticks every once in
a while, but unless it stops by itself that just requires the usual tap
on the accelerator that you use to go back into low idle.

--
Cheers, Bev
1010101010101010101010101010101010101
What do you think you're doing, Dave?
-- Hal 9000

[Paul in Houston TX]

Carburetor throttle rod bearing is worn out and leaking.

[Scott Dorsey]

In article <54e4859e-5a88-4cfe...@googlegroups.com>,

<zekea...@gmail.com> wrote:
>My car starts normally but when I drive it just goes into high idle sometime but when in gear and I pull cluch out it goes down but when I take out of gear it goes to 20000 rpm

So what year and what engine?

Is it injected? I gather it's a manual?

Does it have a cruise control?

Does the butterfly move cleanly and evenly? Is the throttle body gunked
up with crap? Does slamming the accelerator stop it? Does disabling the
cruise control stop it?
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[>>>Ashton Crusher]

On Sun, 6 Mar 2016 05:35:58 -0800 (PST), zekea...@gmail.com wrote:

>My car starts normally but when I drive it just goes into high idle sometime but when in gear and I pull cluch out it goes down but when I take out of gear it goes to 20000 rpm

Does it have an Idle Air Bypass Valve? Lots of Fords do but don't
know about Nissans. It's how the idle speed is controlled on the
fords. The thing sticks and doesn't close as much as it's supposed to
and you wind up with high idle speed.

[Scott Dorsey]

Indeed, or an idle air control solenoid. Either one can get gunked up
and stick just like the butterfly can.