What just happened? (transmission?)

[InvalidUserID]

Hi all,

Quick details: 1999 Civic, 158k, automatic.

Earlier tonight I drove some out of town relatives home to another relatives home where they are staying. Coming off the freeway, they didn't tell me it was the next exit. As a result, I got off the freeway hastily, and had to slow down from about 65 to a stop pretty quickly. I could feel that the shift didn't feel right but felt fine at the light and accelerated normally. At the next red light, the idle was high (2K) and when I dropped off my relatives, I noticed that the car didn't slow down as it should and it downshifted oddly. Basically, the downshifting and RPMs were off.

I shut the car down, it sat for about a minute and I restarted fine but the RPMs were again at 2K at idle in park and when I went to shift into drive, it wouldn't go. After a minute or so, the RPMs went back to normal all of a sudden and I was able to drive normally home the rest of the way. Odd, very odd as that has never happened before.

I'm guessing the quick stop threw the transmission off?

 

[UberxG]

maybe idle air control valve ??

 

[Colt45ws]

Something is making it idle high. As for not going into drive, it may be some sort of protection mechanism, as engaging drive at 2k RPM is basically a neutral drop.

 

[The_Jeff]

Could be related to the vacuum brake booster. A minute is too long for it to refill; maybe the diaphragm has a small tear that only shows up under specific conditions. Causes vacuum leak and high idle.

 

[ARCOgraphite]

Hard to diagnose from here, car is ancient though and things will go south. Sounds like moderate vacuum leak into intake, Check PCV, brake booster, IAC secondary vacuum hoses etc.

 

[SkyGod]

Battery.
Charging system is trying to raise rpms to charge it.
Have battery checked.

 

[InvalidUserID]

Checked battery, it is fine.

Took it for a drive after it sitting over night, drove fine around the neighborhood. Drove it on the freeway and tried to recreate the situation, drove normally.

I'll just keep an eye on it. I'll check back in if anything new comes up.

 

[InvalidUserID]

Hey guys, a bit of an update. Thought about it the past few days to try to come up with any new info or recreate the occurrence.

Under normal driving, no issues. All weekend, no problems at all.

Then I remembered that the night the problem happened, I was coming off the freeway using cruise control. Sure enough, today I recreated the problem: Coming off the freeway at 65, turned off cruise control and slowed the car down. The RPMs stayed a bit high and when I came to a stop, the RPMs were at 1K for 15 seconds or so when it just dropped back under 1K, which is where it normally idles at.

I'm guessing its something with cruise control and reducing the speed coming off it thats playing games somewhere?

 

[NJC]

Originally Posted By: ARCOgraphite
Sounds like moderate vacuum leak into intake, Check PCV, brake booster, IAC secondary vacuum hoses etc.

I'd start here too - esp since original poster indicated it happens after using cruise.

 

[GMFan]

I had an issue with my idle on my Saturn. Turned out to be a $10 Throttle Position Sensor. However, if killing the engine and turning it on doesn't resolve the idle, it could be something different.