High idle issue. (1300rpm)

[EvanH]

Just got my car up and running from replacing my head gaskets, and now I have a high idle.

No vac leaks, assuming the 17inHg is good seeing as its the same as I had before the job.

Things I replaced include:
IAC- from rock auto
TPS- adjusted by the maint manual
PTU
CAS- I adjusted it by eye against where the old one was positioned, measured the casing and marked it.
New knock sensor- reads correctly.

At a slight loss...

[EvanH]

Bump.....

[FeaRpb]

Try leaving the battery unplugged for the night. Hook it back up in the morning and see if that fixes it.

[DrGonzo]

Eyeballing the CAS will not work. It needs to be checked and set with a timing light. I tried marking the position before working on my engine. Always had to adjust it afterwards.

[EvanH]

But does the cas have to do with idle?

[DrGonzo]

Increase/decrease timing will lower/raise idle speed.

[EvanH]

Good to know. Thanks. Would an obd I reader be helpful? And would an autozone timing light be acceptable? The kind you can rent?

[DrGonzo]

You can't have anything plugged into the odb1 port when setting the timing or it will switch it over to set the base idle. I have an Autozone timing light and it works just fine.

Refer here to set it correctly: Stealth 316 - Ignition Timing - DOHC (http://www.stealth316.com/2-ignition-timing.htm)

[EvanH]

I mean in general though for the obd reader.

[DrGonzo]

I couldn't say as I have only ever used a logger and MMCD.

[KeithMac]

Have you adjusted the TPS based on the idle switch position?.

My car idles at -19inhg to -20inhg.

You really need a logger to see what the ISC count is, if it`s 0 the ECU is bottoming out the idle control and you have a leak somewhere after the throttle body.

Deffinitely enough free play on the throttle cable?.

[EvanH]

My throttle is resting on the fixed position stop, my throttle cable is taught but not pulling on the throttle. I adjusted my tps to the book, with the feeler gauge against the throttle stop and my meter on the leads. I have been reading about this idle switch, but I am not understanding where it is located.

[KeithMac]

It`s part of the TPS, you`ve adjusted it correctly with the meter, leads.

If it was idling ok before then you have a vac leak after the throttle plate somewhere..

[EvanH]

Even though the TPS is new, could it be defective?

[DrGonzo]

I never liked the way the manual stated to adjust the tps.

I hook up my logger and adjust it to when the idle switch is activated when closed and not activated when just a hair open. Tried the way the manual stated and it never worked properly. Maybe I was just doing it wrong but I know mine idles perfect at 750rpms.

[BaadVR4]

17" vacuum at 1300 rpm is low. At 900 RPM, my fully built motor holds 21-22" vacuum. First thing, like others have said, is to set your timing. The most common cause of high idle is a vacuum leak.

[EvanH]

My engine has over 150K. Before the job I had the same vac numbers. On down shift was the only time I would see over 20. And when I was trying to diagnose why I was missing coolant, I would rev and hold around 1500 and saw the same numbers. I'm not saying you guys don't know what you are talking about, just trying to provide more insight to you. And again thank you for the help. This is my first trouble shooting issue.

[BaadVR4]

What are using to measure vacuum?

[EvanH]

Admittedly, my boost gauge. Reading the timing section on stealth 316, it mentions idle should be around 700. Mine isn't, so can I safely adjust the timing in the first place?

[DrGonzo]

When you ground the wire on the passenger side the idle will drop. If it does not drop to within 700-850 rpms then you need to do basic idle adjustment.

[KeithMac]

My idles at -11.6psig / 23inhg ish as well.

Cam timing can have an effect on idle as well..

[EvanH]

Anyone know how the Fast Idle air valve on our throttle body works?

[KeithMac]

When he coolant`s cold it opens up a passage way in the throttle body to allow more air into the engine at idle, as the coolant warms up the FIAV slowly closes. It works similar to a thermostat (wax pellet and plunger).

[EvanH]

Well, I havnet timed it with the timing light yet, but I found my problem. The brand new IAC wasnt functioning properly. I took it off in an effort to rule out components by switching with my old ones. Started up, constant idle again.

By the way it looked, it looked about an 1/8 inch shorter than my original stock one. Odd. Now I have to call rock auto.

[BaadVR4]

Glad you got it fixed!