'85 3.2: Potentially bad ICV?

[billh1963]

I've received great advice in some previous posts about fixing my idle hunt problem. I'm only posting this because I have not seen this particular scenario mentioned and want some feedback before I check other things.

I'm pretty confident I have no vacuum leaks at this point.

BTW: Will be installing an AFR gauge in a week or two when I get a chance to get more useful data and, well, just because....

In the meantime, please let me explain the symptoms and see what you think:

Sometimes (not all the time) the engine will have a small idle hunt when starting from cold. If it occurs when the engine is cold, it will clear up within 10-20 seconds.

HOWEVER, I always have it when the engine is up to temperature and I am at a stop light.

Once the engine is warm, if i come off of rpm quickly, the idle will hunt. In other words, if I stop suddenly (say I'm cruising at 3K rpm and suddenly let off the gas to stop) the idle will hunt.

However, if I apply a load to the engine as I stop, it will not hunt. For example, if I pull into the garage while giving very little throttle and then put the car in neutral, the idle is perfect. In fact, if I am at the stop light, put the car in first, slightly engage the clutch for a fraction of second and then go back into neutral, the idle is perfect.

I have cleaned the ICV. I have also tested the ICV (unplugging) and it appears to be working. Could it be intermittent or do I need to be looking at the other causes of bad idle that are so well documented?

[stlrj]

On my 87, if I open up the idle air bypass too much, it will hunt. Try lowering your bypass air by turning it clockwise and you might be surprised. Also, my 86 Carrera had the same behavior, so it must be a common problem.

Cheers,

Joe

[john walker's workshop]

Is your closed throttle micro-switch working? You should hear a quiet click when you slightly open and close the throttle back in the engine area, by hand. Test with an ohmmeter for open/closed at the 2 terminals in it's plug. Too high or too low idle speed beyond 800 can do it also. It wants to correct. Does it vibrate with the key on?

[DaveMcKenz]

Originally Posted by stlrj

On my 87, if I open up the idle air bypass too much, it will hunt. Try lowering your bypass air by turning it clockwise and you might be surprised. Also, my 86 Carrera had the same behavior, so it must be a common problem.

Cheers,

Joe

Hi Joe,
Do you mean the idle speed screw or the idle mixture screw? They both allow air to bypass something, either the throttle plate or the barn door.
Thanks,
Dave

[Jayboundless]

I had the same exact symptoms you described on my 85 3.2. I removed the ICV and cleaned with carb cleaner and it fixed it for a short period then the problem showed up again with the same symptoms. I replaced the ICV and it fixed the issue. Good luck!

[DRACO A5OG]

Let's test your ICV.

Next time on cold start have a screw driver ready. Start her, when she hunts, tap on the ICV with the screw driver, if she clears up, then it may just need cleaning. Do this at stops too when safe to do so.

As above, remove the ICV and use carb cleaner until it comes out clean, finish with silicon based spray lube, just a spritz.

Check the OHMs while you have it out.

If you are getting the AFR tool, check for proper AFR after she is HOT. doing it cold or warm will give you false readings then set base idle jumpering B&C.

Break a Leg.

[stlrj]

Originally Posted by DaveMcKenz

Hi Joe,
Do you mean the idle speed screw or the idle mixture screw? They both allow air to bypass something, either the throttle plate or the barn door.
Thanks,
Dave

It's the one on the throttle body. It adjusts the base idle speed so the ICV will work properly. It's facing you as you look at the ICV. You'll need a 7mm socket.



On mine, there was no slot for a flat blade screw driver but a 7mm hex deep inside. Turn it clockwise to eliminate surge.

Cheers,

Joe

[billh1963]

Quick update: Drove the car almost 100 miles on Saturday and no idling issues. Did not do anything new. I believe the ICV was somewhat sticky after cleaning and is now working properly. Time will tell!

Thank you for the input.

[DaveMcKenz]

Thanks for the tip, Joe.
Bill, glad your idle problems are better. A new ICV may be in your future. About $300, as I found out.
Dave