Low Idle Speed

[Zedhead]

Been fighting a low idle speed for a while.

1998 LOBW- Engine warm, it idles at 2-300 rpm in gear, foot on brake.

I've cleaned the IAC, new TPS set to .5v throttle closed.

I need to clean the TB, But, I doubt that will give 400 RPM idle speed.

Any idea's would be appreciated

[Huffer]

What does it register with your foot off the brake? If it goes up, you maybe are like me and need to start budgeting for a new alternator.

Are you measuring idle with a scanner or by eyeballing the tach? The tach starts at 500rpm...

[Zedhead]

Eyeballing the tach, I can feel the engine is idling to low. there is a pronounced 'off idle' dead spot.
Seems to go away if I hold the pedal so it idles at 750-800 rpm.

Idle in neutral, when warm, is around 400 rpms (per tachometer)

[Huffer]

Unless youre reading off the scanner, your eyeball cannot read 400rpm.

[Zedhead]

Well, I'll haveta go warm er up and plug er in. But I can tell it's to low. The off idle hesatation is very annoying.

There are 5 ticks between 0-1000 rpms on the dash, it reads 200-250 rpm in gear at idle

[Huffer]

How many ticks between 1000 and 1500?

[Zedhead]

2.5

[ShadowGT]

Loosen the throttle position sensor and twist it forward a little bit while the car is idling. Not a lot, just a hair here and there. Helps to use a marker and make a tick mark in it's current position to give you a reference.
If you took the TPS out or fooled with it in any way, you might need to physically rotate it a little to find 700 RPM.
The ECU does try adjust to 700-750 RPM at idle but that sensor needs to be pretty close to ideal in position so that the ECU can figure it out.
Too far one way, you get the CEL for higher than normal range idle. Too far the other, it idles low.

I'll just throw the disclaimer in there: Results will vary, thats just what I noticed on my car when I put a different TPS in.

[jey]

2.5

:shock: I've never seen a Legacy without at least minor tick marks at the 500-rpm interval. Every 2nd gen I've been in has had the most minor tick marks at 100-rpm intervals.

[Perkul8r]

I know my 04 Leggy idles really low too. Low enough that the lights and everything dim at idle in gear. BUt its always done it since I have had it. And everything has been checked out at the dealership. I am gonna go for a drive here shortly, but i think it only idles at like the second mark above 0 on the tach.

So i just ran to the grocery store real quick. And on my car there are only two marks between 0 and 1000. And at idle in gear its in between them.

[Zedhead]

Loosen the throttle position sensor and twist it forward a little bit while the car is idling. Not a lot, just a hair here and there. Helps to use a marker and make a tick mark in it's current position to give you a reference.
If you took the TPS out or fooled with it in any way, you might need to physically rotate it a little to find 700 RPM.
The ECU does try adjust to 700-750 RPM at idle but that sensor needs to be pretty close to ideal in position so that the ECU can figure it out.
Too far one way, you get the CEL for higher than normal range idle. Too far the other, it idles low.

I'll just throw the disclaimer in there: Results will vary, thats just what I noticed on my car when I put a different TPS in.

The ECU needs to see the TPS .5v with the throttle fully closed. If You move it forward, it will actually think that You have stepped on the gas pedal, and respond accordingly.

[Huffer]

How many ticks between 1000 and 1500?

2.5

:shock:
Here's a pic of a 1998 GT cluster:

https://sl-i.net/FORUM/images/imported/2010/12/e47a8d37-1.jpg

[Zedhead]

My OB has ticks all the way down to 0

I'll get a pix when the Little Woman gets home from work.