Hey everyone-

Two days ago my idle speed jumped from 800rpm to 1700rpm. Additionally, my boost dipped from 10psi to about 9psi. Otherwise the car runs perfectly. Sounds like an intake leak... but I can't find it!

I pulled off the intercooler accordian tube and covered the inlet to the elbow - the idle speed dropped, but the car stayed alive. So, it isn't the idle speed regulator holding open or anything like that.

I also looked for vacuum hoses... but the giant increase in idle speed couldn't be due to a little, baby-sized hose. More air than that is leaking.

Do you think the ACV system could be culprit? Or the EGR system? I'm not familiar with how these guys work. Any other suggestions on stuff that would suddeny, without warning, jump the idle speed that much?

I've driven the car a couple hundred miles since then (the holidays necessitated it!), and it has not gotten any worse. This, to me, tends to rule out manifold leaks... they'd usually get worse with time, wouldn't they? I dunno...

Any suggestions? BTW, the engine is completely stock... no modifications whatsoever.

Thanks in advance! And happy (belated) Thanksgiving!

Take care,
Shad

 

im assuming you have used starter fluid on allt he joints to try to find the intake leak so i will suggest you unplug all the things which control idle such as the...

dashpot
ISC
AWS
Wax rod assembly
fast idle screw
the airpump solenoid

(oh yeah, if you have not done the starter fluid trick to finding that leak, have a fireextinguisher ready just incase and only shoot a little bit at a time)

 

Hello-

Thanks for the reply!

The Dashpot, ISC, wax rod, fast idle screw, and AWS all allow air to bypass the TB from other parts of the intake system. Putting my hand over the elbow and blocking 100% of the air to these guys and still having the engine run means that it probably isn't them... <sigh>. Plus, the 900rpm idle it does when the headlights, etc. are on still works... it makes the idle go from 1700rpm to 2200rpm :-).

The airpump solenoid... all I've done here so far is pull off the airpump clutch wire and block the inlet to the pump. Oddly enough, it does drop the idle speed a little, but even blocking this and the intake elbow simultaneously doesn't make the car die. D'oh!

I haven't yet gotten a chance to get starter fluid down around the LIM connection. But remember - I'm looking for a BIG leak. For fun, I pulled off a couple little vaccum lines and the PCV, and the idle speed changed a little, but not much. This tells me that the leak is nothing small. I'm not familiar with how I'd go about forcing the ACV to shut off all possible airflows... any nice schematics on how it works? I tried the service manual, but it wasn't that great in showing me how it could let a giant leak go by.

Thanks again!

Take care,
Shad

 

^

 

Check your throttle cable. Push the trottle cam to manually close it a bit. Mine got stuck and I got a 2000 rpm idle.

 

Thanks for the reply!

I did. It's nothing to do with the TB.

The airleak is coming from somewhere more "deep" inside the intake system. I know that. That's why I'm asking about ACV, EGR, etc...

Take care,
Shad