3.2 idle not steady
 

My 3.2 idles at 800 rpm but bobs up and down 2-300rpm. It also does this when cold but at 1100rpm. It just bobs up 2-300 rpm and back down. The searches I've done came up with idles that were more erratic than mine.

I've sprayed around with a can of engine starter but no change was noticed. Any one experience this particular problem? TIASmileWavy

Check that the idle microswitch consistently activates when throttle is closed. Clean out the idle control valve from any gumminess. If you don't have any vacuum leaks, then you'll need to adjust your idle mixture under the air flow meter, and readjust the base idle speed.

When it Hunts (as you stated bobs up and down), keep the engine on and use a screw driver and tap on the Idle Control Valve (ICV). If it clears, it may be gummed up as stated above or faulty.

If suspected to be Gummy, take the ICV off and thorughly clean it's inside until clear spary some lube silicon based not WD40 please. Re-install and test. If it persist do the following:

Take a digital multimeter to the electric terminal when engine is off on the ICV. The center terminal plus any of the outer terminals should read a minimum of 20 OHMs. The outer terminals should read 40+ OHMs. Simple fix just swap with new one. Check the new one before you install.

My mechanic said it could also be the O2 Sensor, my next project.

ok, I have a stupid question
where is the idle control valve located?

found it in the parts diagram
how do you clean it?

Undo the hose clamps and the wiring connection, use injector cleaner or ether and dump it in where the hoses hook up to. I used nitrile gloves to cover both ends and swirl it around inside, do this a few times until it looks clean - then use silicon base spray to lube it. Re-install. There are a couple of threads on this that explain it better than me, search for ICV. I just did this last weekend and it helped.

I am reading through the searches now.
sounds like cleaning is pretty straight forward, thanks!
but the electrical testing goes straight over my head.
I have no idea what they are talking about

Get youself a Digital Multimeter to test the terminals of the component to read proper OHM's. When you get the meter, it will explain in detail how to use it.

What's great is most meters have a "Short" indicator mode to find those annoying circuit shorts. It is a must tool.

I will do.
I try to understand the terms but it is not easy
lol

LOL, Brother,

I spent 2.5 hours last night with another memebr looking up WUR, to find out later it was not for my year, I have a WUV.

Don't be shy ask anything here, we all try to input for the P community.

I have noticed that for sure
I know I don't know
of course my biggest fear is breaking something that isn't broken when i try to "fix" it
lol

Been there Done that.

I replaced the Cylinder Head Temperature Sensor located on the #3 cylinder head and routed to the engine connected to a three connection key. I was so carefull but due to age and heat the plastic just fell apart when I disconnected it. I stayed calm and had some thick rubber heat resistant tape and taped that sucker up. It is actually add better heat protection and no risk of moisture instrusion.

Feel free to ask before you do.

I use the Carrera manifold on my turbo, my idle was doing the exact same thing when I completed the rebuild.
Try adjusting in this screw in on the throttle body, it should turn easily, don't be afraid to turn it in 3-5 turns, you can always put it back where it was, count the turns.
This solved my idle hunting problem.
Good

Luck.http://forums.pelicanparts.com/uploa...1196195478.jpg

what does it do?

It's the air bypass adjuster, by threading it in you reduce the amount of air by a small amount at idle, this circuit is bypassed as soon as you a crack the throttle.

Here we go...http://forums.pelicanparts.com/porsche-911-technical-forum/370635-carrera-3-2-idle-fluctuation.html

yeah Zef I have been reading through that thread as well
there is a ton of info on this issue
seems all different kinds of solutions are at play

just gave this a try. and it really smooths things out a lot
idle was not hunting so much but right off idle there was hesitation
now it is gone.
still need to check the ICV electrically
that will be my big achievement for sure

You can take that screw all the way in if you're getting an improvement, don't be afraid of tweaking with it.

ok, thanks again.
every little bit helps
very cool how little steps and ideas work wonders

I just went through this myself. My idle was surging badly about 600-800 rpm.

I suggest first buying the Bentley Manual, and doing the sequence of resistance checks to eliminate the sensors and throttle switches as problems.
You can check your throttle bypass valve manually by taking it out once the engine is warm, and looking down the throat to make sure it is holding steady at halfway open.

If all of the electronic sensors and afm checks out, then you have to start looking for vacuum leaks. You can sort of confirm this by listening to the bypass valve working while the car is idling. Anyway, there are a LOT of places where a vacuum leak can occur. I found it very useful to have several good work lights and a good sized inspection mirror. You will need to take hoses off everywhere and inspect the ends, and replace hose clamps. The hose clamps on the ICV can be tightened up a bit with a pair of sidecutters.

Stick with it, and you will be rewarded by a sweet running, very reliable and more powerful motor.

I've cleaned the ICV, the idle micro switch operates properly and still the idle bobs. Now as for the ICV resistance values; they are 16 Ohms and 20 Ohms (from center pin to outer pins). I'm off by 4 Ohms on one side. That's out of tolerance by 20%:eek: Would you consider this the definitive source of my problem?

I've got a spare ICV you can try. Send me an IM and we'll work things out.

T...

Trog, you have mail.

Bingo, we got a winner :eek: after 20+ years, it's time to replace it

I think you can get that much error from one multimeter to another, or dirty contacts, etc.

I think your problem is somewhere else. Keep going, and check the cyl head temp sensor, the air flow meter box, the full throttle and closed throttel switches, and the adjustment of the throttle microswitch.

I'd also do a visual and handcheck of your vacuum hoses. Look for cracks, or signs of oil blowing out through a crack.

+1 on that, check to make cerain the meter is known to be good.

Check the OHM's on all components and elliminate before you replace.

Get some ETHER (started fluid) to check for Vacuum Leaks,

Best wishes Brother,

+ 1 for Steve W recommendations. I did the same things in that specific order. Verify hoses for air leaks, cleaned and lube the ICV, re-adjusted the AFM to 6.5 turns and re-adjusted the idle control. Car now idles at 850 steady. Still have to fine tune it for accuracy but I am more than happy with it now. Own the car for over a year, no P car expert. Did a lot of research here.

I agree, one meter to another: but you won't get that much error from the same meter. One side read 16 Ohms while the other side read 20 Ohms consistently as I checked and re-checked. It's now a known out-of-tolerance part in my eyes. I'll swap with a known good unit and see...I don't want to start chasing something else while I have "one in the hand". ;)

ok,
cleaned the ICV with carb cleaner and then shot it with silicon lube.
that is a definite to do for any body suffering any kind of hesitation for sure.
I think that actually cleaning the ICV should be the first thing
so I've also replaced the dme relay
the cht sensor
plugs and wires
distributor cap and rotor
back in april the alternator was replaced.
tried to rebuild it but it was shot and the guy who did it didn't charge me for the rebuild after it didn't work. good guy. put in the new alternator and it works fine
I still have the O2 sensor plugged in and put a SW chip in a few weeks ago
just took her out for a spin to warm up and see how the idle is
runs really great
better than it ever has
of course this is the only 911 I have ever driven so it is tough to know if it is really spot on
with the O2 sensor plugged in it feels real "cammy" feels like it picks up in steps
and with it unplugged it feels linear but not as fast revving
don't know if any body else gets that reaction from the motor
and the stumble I had at 2500 rpm is gone
hopefully for good

Sounds like the idle mixture needs to be adjusted, along with the base idle speed. See the following threads for more info:

http://forums.pelicanparts.com/porsche-911-technical-forum/376357-rpms-hanging-s-wong-chip-rough-idle-again.html

http://forums.pelicanparts.com/porsche-911-technical-forum/104495-idle-hunting-problem-continues.html

Hi Guys,
I have an 87 with 42k. Runs great. On cold start it idles at 1200rpm for a few minuets then goes to around 850 or 900 rpm. It then hunts very slightly. Maybe 50 rpm up and down at most. This certainly isn't a huge problem but is it the start of a bigger problem? Do you think I could benefit from an ICV cleaning? Do these cars ever idle at around 850 or 900 without any hunting whatsoever?
Thanks,
Jeff

01sport,

I'm certainly a novice at 911 issues.......but I cleaned my ICV last weekend due to a stalling problem and now she idles at a rock solid 850 rpms.

01Sport,

If the ICV has never been changed, it will be going on 26 years, bound to build up gummy oil in it and the electronics in it could be failing.

Your Baby must warm idle at 880 RPMs (+/- 20 RPMs), it must not HUNT! HUNTING IS NOT NORMAL

Try the cleaning, slight lube and test the OHMs just to be certain, replace if necessary. It is quite easy and Pelican Parts sells them.

I'm no fuel injection expert, but I stayed at a Holiday Inn Express last night......an '87 with 42k miles?

I think your main problem is that you don't drive the car enough, and expect it to run perfectly after sitting for years with no use. Seriously, these cars need to be driven. Putting them back into use requires checking hoses, brake componets, flushing fluid, checking or changing belts, oil leaks, and the list goes on and on.

I'd say your 911 is running admirably well under the circumstances.

300 thanks for the reply. Exactly what I was hoping to hear.

Your Welcome SoCali ;)

when I want to adjust the idle
how do I jump the plugs?
I am sure that sounds like a stupid question

I believe you can disconnect the ICV, set to your year's specs the re-plug it in. Other's more tech should hopefuly post.

My Mechanic hooked up a device in the round terminal on the driver side wall of the engine compartment to check my idle. He said it disabled the ICV. I figure disconnecting the ICV would be the same thing, no?

I have no idea
but I have to conect those two plugs some how to adjust the idle