Adjusting idle on non-DBW throttle

[six]

So, I want my Vic to have a higher idle... Is it as easy as adjusting the idle-stop screw for the throttle handle?

Will there be a danger if I happen to set the idle too high, besides increased fuel consumption?

How will I know how high to set it, if there is no tachometer?

Thanks

[fa22raptorf22]

How high to set it? Listen to the engine. Do what sounds good to you.

How to set it? Depends. If you have an idle air control valve, that will do the idle automatically, but if you just have a carb and or butterfly, then just do what you would to a lawnmower.

[six]

Yes, it has an idle air control valve, but that only trims the idle in response to changing conditions (cold start, A/C compressor kicking in, increased alternator load, etc). I want to increase base-idle.

I did some research, and apparently, there should be a another screw that is on top of the throttle body that can adjust idle (called the throttle air-bypass screw, don't know if the Vic has one, gotta check), in addition to the idle-stop for the throttle handle. Which one should I use?

[theholycow]

Do not use the stop for the throttle. I'm pretty sure that's the incorrect way to adjust idle on any car.

You'll put slightly more wear on your automatic transmission every time you put it in gear, and you'll generate a little more heat sloshing the fluid when stopped in D.

Why do you want to increase your idle?

[six]

I want to increase my idle because it has become a little low, especially now that it's warmer, it's much more noticeable. Since I have no tachometer, there is no way I can tell how much it's low by, but it's definitely lower than before. And I've put in a new IAC valve, new fuel filter, and cleaned the fuel system. The car runs fine at all times, just idles a little low.

[LHOswald]

Do not use the stop for the throttle. I'm pretty sure that's the incorrect way to adjust idle on any car.

You'll put slightly more wear on your automatic transmission every time you put it in gear, and you'll generate a little more heat sloshing the fluid when stopped in D.

long story short, the vehicle is trashed. time to get a manual again!

[six]

I know, I know! I'm looking!

[theholycow]

Why does it bother you that it idles low?

I'd prefer if my cars idled at 25rpm, if they could without stalling.

[six]

So it's okay to have it idle low? It feels kind of rough, like if it idles any lower, the car will stall and die. If it's okay, then I'm fine, I was just afraid it might be bad for the car in the long run.

[theholycow]

If it's rough you ought to bring it up, but you really ought to troubleshoot what caused it if you care that much. Just increasing the idle will merely make you more comfortable, which is a fine goal too.

Have you checked for stored codes that aren't setting the check engine light?

Have you cleaned the MAF?

[six]

Frankly speaking, I'm probably not going to be driving the Vic for much longer... Haven't checked for codes or cleaned the MAF yet... maybe I'll clean the MAF next, but it doesn't really matter much any more. Since it runs fine at all times sans idle, I'll probably just leave it. Thanks for the advice.

[1974Alfa5spd]

Doesn't the IAC thread in? (Sorry if that's not how they work, I've never seen an IAC before much less adjusted one) If so, thread it in a little (like in 1/8th turn increments) with the engine idling until you get the idle you like. IIRC these 4.6s are so dumb they might as well be carbureted.
Like THC said though, throttle-stop screw is NOT the way to do it.*

* Posted as a courtesy to anyone who happens to find this thread via Google

[six]

The IAC in the Vic doesn't thread in. It's attached via bolts, with a gasket in between. I've replaced both the IAC and gasket in an effort to remedy the rough-idle (the old IAC was so filthy in needed to be replaced anyway).

[six]

Have you cleaned the MAF?

Hi THC. So, I went ahead and gave the MAF a good cleansing, along with a new air filter, and unplugged the battery for half an hour to reset the ECU.

I will have to drive it more to see, but it seems like it fixed the issue. Idle is stable now, and not too low. Can't believe it was a MAF problem. I'm going to be going in for 100k mile service, so I will receive a new set of spark plugs, plus all fluids. It will probably run like new at that point.

[1974Alfa5spd]

Remember, it spent 50% of it's life idling, and the other 50% at WOT. It doesn't surprise me that the MAF was in need of some attention.