Idle bounce down vs up? difference

dsmyth · 06-16-2010, 07:18 PM

I have read the posts on idle bounce and they all refer to bounce up. For the first few minutes mine drops to 500 then pops up to 1000 then steadies at spec and bounces that way . I have a new ICV, oxygen sensor, fuel pressure and damper, wires, plugs, coil ect. .Just recently installed a 964 cam but it did it with the 3.2 cam. I know this topic has been well covered but I have run out of ideas. I can live with it as It does go away but I would rather solve it. thanks Doug

johnsjmc · 06-16-2010, 07:23 PM

Is the car chipped? Light flywheeland aluminum pressure plate? Steve Wong says he now has a fix with his latest programs for dip. . I suspect he uses the idle switch to momentarily push the timing foreward to boost the idle speed .That would react faster than an icv could.

Hendog · Hendog's Garage

I chased an idle dip for a while, OK for a few years... I replaced same stuff you did less the cam. I finally replaced the intake gaskets and spacers. It was a intake leak that caused my idle to dip from about 880 to 800 or so.

dsmyth · 06-16-2010, 07:52 PM

I did just replaced the clutch with a lightweight unit but it was happening before that. I also replaced the cylinder temp sensor and all the intake spacers and gaskets. I have double checked the vacuum hoses.

86 911 Targa · 06-17-2010, 02:11 AM

Quote:

Originally Posted by dsmyth

I did just replaced the clutch with a lightweight unit but it was happening before that. I also replaced the cylinder temp sensor and all the intake spacers and gaskets. I have double checked the vacuum hoses.

Just a thought.

Had the same issue a while back.

How about the vaccum lines behind the throttle assy?

Could they be transposed or not connected?

Good luck,

Gerry

dsmyth · 06-17-2010, 04:33 AM

I will check the vacuum hoses again Gerry but they seem to be properly attached. thanks Doug

kidrock · 06-17-2010, 07:39 AM

check your air / fuel mixture, could be running a bit rich

dsmyth · 06-17-2010, 06:46 PM

The vacuum hoses seem to be all correct. Is it safe to just try leaning the mixture a 1/4 turn to see if that solves the problem. I don't have any measurement tools that would be needed to gage this?

Hendog · Hendog's Garage

Quote:

Originally Posted by dsmyth

.Just recently installed a 964 cam but it did it with the 3.2 cam. I know this topic has been well covered but I have run out of ideas. I can live with it as It does go away but I would rather solve it. thanks Doug

Just covering the bases here; you did a valve adjustment right?

kidrock · 06-18-2010, 09:45 AM

Doug,

I took the liberty of searching a thread which contains excellent advice on your dilemma. It's a bit of a long read, but very informative...you could probably start around page 3 and get a handle on what's happening. Good luck.

idle bounce

dsmyth · 06-18-2010, 09:04 PM

Not sure where you are going with the valve adjustment Henri but it was required after the cam installation. What are you thinking ?Thanks for the link Kidrock thats got lots of good info in it.. Doug

Hendog · Hendog's Garage

Quote:

Originally Posted by dsmyth

Not sure where you are going with the valve adjustment Henri but it was required after the cam installation. What are you thinking ?Thanks for the link Kidrock thats got lots of good info in it.. Doug

Just making sure the obvious was done, ie the valve adjustment. I know the engine would be exhbiting greater running issues had the valves not been adjusted but I stuck my neck out just in case it was something weird like that

You see some things you'd never would have thought now and again.

So, back to chasing the vacuum leak.