drew_816

I went to get my car smogged today and it passes emissions very nicely. I failed the test, though, because my idle is slightly too high. So I spent $90 for nothing.

The mechanic told me I should adjust the idle and bring it back for another $90 reaming. I don't want to do it myself and fail to do it right and drop another 90 bucks, so what's the right way? I have been told that it is controlled by vacuum so I may have a leak. What hose would it be and how do I test it?

I'm a little pissed that the state can tell me that I cannot drive my car unless it has an approved idle speed. They don't know the first thing about my shark. It's a big beaurocratic crapfest imho. Anyway, I've vented. Can anyone help me out?

Thanks in advance

Rich9928p

Drew,

You didn't mention how fast your engine is idling. If the fast idle isn't caused by a vacuum leak, then it is VERY simple to adjust the idle speed.

Your '82 (if it is a US model) has the L-Jetronic injection. The idle speed adjustment is accomplished by "trimming" bleed air that is let into the intake system. If you look to the front center of your engine, down under the intake system you should see the throttle body. On the front of the throttle body is a very large flat head screw. All that you need to do is turn that screw clockwise to reduce the idle speed. The factory recommended idle speed should be on a stick on the underside of the hood. The tachometer in your dash may read a little high, so I recommend using a more accurate tachometer for setting the idle speed.

drew_816

Okay, I think I found the throttle body. I was looking for a device with cables attached from a friend's advice and I think I found the mysterious machine. Is this it?




Where is the flathead screw? I pushed the cable attachment and the engine made a loud noise. So, as you can see, I have made a thourough scientific analysis of the problem.

Thanks for the post, I'm relieved that this might be as simple as an adjustment.

User 4221

This shows it... It's behind the oil fill tank

drew_816

great, I can adjust it now.

ty

I am not sure I can measure the rpm though. I have a multimeter that may do tach, but where do I stick the leads. the distributor?

ViribusUnits

No. Don't even try to stick it on anything on the distributer.

On the ignition coil, there are two screws with wires attached. One goes to power supply, the other the pulsed ground. IIRC, you want the bottem one.

The ground of the tach goes to the frame.

Watch out thought, some one might have increased the idle to cover up for something else.

Good luck.

drew_816

Thanks for the reply, ViribusUnits.

Could you elaborate on what that might cover and what symptoms I should look for? I have reason to suspect that the PO very much wanted to cover any problems and lied to me about a number of things.

User 4221

You're welcome

ViribusUnits

Usualy, it's a rough idle. You see you can increase the idle speed to cover up for a rough one. A rough idle can be caused by any number of things. The first on the list in my mind is a vacuum leak.

You'll know when you adjust it.

drew_816

My multimeter has a "TACH" mode and when I attached the multimeter positive to the lower screw on the ignition coil it gave me a reading varying from 9.8 to 1.3. I adjusted the control screw until it fluctuated between 7.3 and 7.7.

My negative lead was attached to nothing. When I attached it to the frame I got a consistent 0 reading and when I attached it to the upper screw on the ignition coil it gave me a signnificantly higher reading.

I am inclined to assume that since the positive to coil / negative to nothing was so close to the indicated range of 700 - 800 and I was so easily able to get it into those readings (no rough idle) that I did it right.

There is a sharp hissing sound that was getting slightly louder as I closed down the idle control screw. Maybe I just didnt hear it before. Could it be air escaping from a vacuum line with more and more pressure as I close down the idle setting?

ViribusUnits

It's possible that you have a vacuum leak. If your curious, you need to do the whole lets miti vac all the lines, and the "put an inner tube over the intake" trick.

Does the tach on the dash agree with your readings?

drew_816

yes the dash tach agrees

ViribusUnits

You might think about checking your ignition timeing.

A possibility is that someone did a timeing belt job, and the new belt was not exactly as long as the old belt. the result is the timeing is advanced over what it was before they buttened it up. The few degrees of advance will result in a few hundrad extra rpm.

Resulting in a fast idle, without changing the screw, or a vacuum leak.

It happened to me, thats how I can know it can happen.

onebad928s

drew_816,
your in california?right? im not sure how far you are from Devek (BELMONT CA.) or 928 international (Anaheim Ca.) but if your close why dont you take a ride there and have them do it correctly with hopefully no hassle. Either that or find a inspection station that deals with high performance street cars (most likely where all the ricers would go)

Lou
83 928 5speed

drew_816

I managed to turn the idle down and passed the test. I was 127 of an allowable 128 HC (hydrocarbons)! I got lucky.

Thanks for the help!