checkmate1996

Ok,

So the car has been running GREAT for the past couple of weeks. Idles great, starts great, runs great. Well, the honeymoon is over.

HISTORY:
The past couple of days I've noticed that after sitting cold it starts up, idles high and then the AAV closes and we are good to go.
ISSUE:
But then I may go back several hours later, restart the engine and the idle starts on its way down as it should and gets to about 1100 RPMS but then it GOES UP. it holds at about 1800 RPMS.

This problem is random as I have not been able to reproduce the issue every time. I'm 99.9% sure it's *NOT* a vacuum leak since the problem is random and I just replaced ALL vacuum lines with silicone hoses.

I verified the the AAV IS closing or was closed when the idle was high.
Cold Start Valve was recently checked within the last 3 weeks as not leaking and working properly.

So now I'm guessing...that the WUR would be the most logical suspect on this one?!?? I would think a leaky injector would show up all the time.

Also, even when the idle is high, she still runs good, no stumbling or bumbling. STRANGE...

My first thing that I'm going to do is run a bottle of techron through the system...

Other than that, any other initial troubleshooting ideas would be greatly appreciated...

hupp

This does'nt sound like a fuel issue since the car is running strong. Usually issues with the fuel components result in poor running not high idle. Sounds like air is bypassing the throttle body butterfly. Here is a quick list of the things I can think of:

- Leaking around/failed decel valve (big solenoid on the side of the throttle body)
-Leaking/failed idle air solenoid (for the AC)
-Leak at any intake seal or gasket.
-Double check for vacuum leaks.
-Check your idle speed adjustment screw -- just to make sure it has not vibrated loose for some reason.

Also make sure that your throttle or cruise cables are not hanging up.

SharkSkin

I don't think the AC idle solenoid can flow enough air to get you to 1800RPM.

Try plugging the large vac hose that leads to the brake booster -- ideally disconnect it as close to the engine as possible, so you also eliminate the cruise solenoid and all interior stuff from the equation. If the problem goes away use the process of elimination from there.

Using my vivid imagination here -- maybe you have a booster(or other part somewhere) that only leaks when the vacuum gets high enough. As the AAV closes it increases the vacuum, till your leak opens -- then opens wider, bringing you to 1800RPM. You did install the AAV right way round, didn't you?

Also, do you have an EGR valve? Decel pot?

checkmate1996

Thanks guys for your input. I will check the brake booster area next.

Decel POT? EGR valve? Comeon guys this is a 79!!!

If I do, I have no idea where it's at!

SharkSkin

Brad, 78/79 US cars had it -- It is at the other end of the tube that connects to the plenum in the attached pic(flange circled in red). Normally, the EGR valve should be closed at idle, and if it were opening it should cause rough idle and stumble. If the plumbing for it leaks anywhere though, it's a vac leak -- high idle.

The decel pot keeps the engine from returning to idle too quickly, and if malfunctioning can cause a high idle. It's a diaphraghm device, you can barely make it out in the pic below. On a straight line between the EGR flange and the AC idle solenoid in the attached pic, it's about halfway along that line and a little to the left.

checkmate1996

Dave,

You mean the 'big round thing' attached to the plenum?? I never knew that was a decel pot. The PET always referred to it as a vacuum limiter. Now I know what it's suppose to limit!

Is there anyway to test this thing? It's a PITA to get at...

Also,

I have the euro s Hybrid top end, so I have NO EGR (atleast on my setup) and AC solenoid DELETE( I did this one). So I guess we can eliminate those two items from the troubleshooting list.

checkmate1996

• Leaking around/failed decel valve (big solenoid on the side of the throttle body)
o Top of the list to troubleshoot
• Leaking/failed idle air solenoid (for the AC)
o AC Solenoid DELETE
• Leak at any intake seal or gasket.
o Will need to check this
• Double check for vacuum leaks.
o Will do
• Check your idle speed adjustment screw -- just to make sure it has not vibrated loose for some reason.
o Done - Solid
• Also make sure that your throttle or cruise cables are not hanging up
o Done – No hangups

SharkSkin

Brad, you can check the "vacuum limiter" by disconnecting it and plugging the ports to see if the problem goes away. Or you could use the pressure/smoke method to see if it's leaking externally, but that's not a definitive go/no go test -- only a check for external leaks. Depending on the condition of the hoses, you may be able to disconnect it and plug the ports without having to take it all the way out.

Sounds like maybe you ought to check the vac line to the booster a bit more carefully, e.g. disconnect it to see if the problem is in that circuit.

checkmate1996

Ok, I think it was just a little spat. Honeymoon may still be on.

Two nights ago, I started her up, I got lucky as it immediately went to high idle. It held at 1800RPMS. I let the engine get to operating temperature and opened the hood to see what I could see. The first thing I did was squeeze the vacuum line going IN to the AAV. As soon as I did that the idle dropped.

WTF? I though I checked this the other night and it appeared closed. Well obviously it wasn't closed all the way. So, now I'm thinking it's stuck. So I take off the AAV and look down in there and sure enough it's not completely closed. I took the AAV and stuck it into the freezer for about 15 minutes. I took it back out and now it was completely open. I hooked up a 12V source to the AAV and then slowly watched the AAV completely close. WTF? Now what. So I'm thinking it's it not getting ENOUGH electric to completely close. I check the wire harness side plug with a test light. All is good. IHowever, when I look at the plug directly, one of the sides is boogered up. I took a small flat blade and straightened everything out. Then I looked at that AAV plug. Heavy corrosion. Cleaned that up. Put everything back and it appears to be working great for the last 24 hours.

So here's to keeping my fingers crossed and resolving that problem!