Hi all.

I have an '82 GSL with 66K miles (it was an RV tow behind for much/all of it's life, so drivetrain has far less wear than that on it; it hasn't consumed any oil so far in the 4 years, 3,000 miles I've owned and driven it).

Anyhow, it has a super low idle right now: about 400rpm.

It really isn't a problem once warmed up but in that 5 min or so between cold and warm and after the choke has gone in I've got to be diligent and feather the throttle to keep it from stalling.

So I would like to get it up to above 600 at least.

I used the Haynes book first to try and figure out how to adjust the idle, but my carb doesn't have the "over under" idle-mixture screws that the Haynes book shows, nor any of the other carb configs shown in the in the supplemental revisions section (including all the California emissions options)

Nor do I have the idle screw on the right (firewall) side of throttle cable plate that is shown on some other "how to set the idle" threads on this forum.

The throttle cable plate has four (4) cables going into it: one for the throttle, one for the cruise control, one presumably for the choke and one I have no idea where it comes from. But no idle adjustment screw on the right side of the plate.

Right now, it seems to me that the only way to raise the idle speed would be to tighten up the throttle cable, i.e., take all the slack out of it so it'll open the butterfly a tiny bit. But not exactly how idle is supposed to be set.

I've probed all around the carb with a borescope and thus far have not found anything remotely looking like an idle or air mixture screw.

Below are pics of the throttle cable mounting plate.

Anyone ever seen one like this or have thoughts on how to set the idle?

 

The idle speed screw is below all that.

If you DON'T have that, you may have a series 1 (1978-80) carburetor. Those idle with the throttle plates closed, and have an idle air screw right above the idle mixture screw. One very large flat flathead screwhead above the traditional cross headed idle mixture screw.

If you have one of these, note that raising idle speed will make it run leaner and lowering idle speed will make it run richer, since the idle adjuster opens up an air passage that bypasses the throttle plates entirely. It becomes a bit iterative adjusting one then the other.

But with the low mileage, and the dual diaphragm choke pulloff, that REALLY looks like a series 2 carburetor. I am thinking that either you're just not seeing it, or it backed out and fell off somehow.

 

its kind of under that bracket, you also might check for vacuum leaks, its more likely there is a problem somewhere

 

Here is a pic of my stripped Nikki carb. You can see the adjustment screws...I have no idea which one is which, this is my first 7 with factory carb...my other ones always had Webber carbs, but you can see one under the acceleratior cable bracket and one at the left in the bottom middle... marked with an arrow....

Hope this helps you...

 

The pics help tremendously. Thanks.

Don't think I have a vacuum leak anywhere as ALL the hoses look brand new, and once sufficiently warm, it'll hold 400rpm idle all day without any hunting or other tell-tale signs of a vacuum leak.

I note that your carb only has 3 cable tangs(?) while mine has 4: could this be because I also have a (fourth) cable for cruise control?

I can see the arm with threaded rod and the locking nuts on it, but not yet that brass screw that's set back a bit further. Guess I will need to bend in there more and maybe even take the borescope to it.

If this were logical, the screw on the right would be the idle adjustment and the one down at the base (throat/plenum) of the carb body would be the air-fuel mixture.

Anyone know if that is right?

 

You are correct, the one on right (under accelerator pump) is the idle screw and works on the linkage. The other is idle mix screw.

 

The idle mix screw, from factory, also has a big metal cap.

 

I don't know about the extra cable thingy...my 7 also came with cruise control....but I never cared for it so I eliminated it...

 

Great side view pic. Thanks.

It works on the linkage? Somehow in the body?

I was assuming I turn idle screw out (counterclockwise assuming a right-hand thread) to increase (air or fuel and therefore) idle speed, but maybe not if the action is directly mechanical?

 

Yes it's all mechanical. The other end of that big screw contacts a tab on the linkage and sets the minimum gap for the primary butterflies. It's just hard to see with the choke on the carb and all emissions parts in place. I had a hard time finding it the first time too.

 

Do you know which way to increase the idle?

Based on what you said about it being mechanical (and not direct fuel metering), I would now assume (first 3 operative letters spelling "***") that I need to turn it in/clockwise (again ***uming a right-hand thread) to open the butterfly(s -- you used plural; is it a single or dual barrel carb?) to raise the standing idle?

I had asked earlier in this thread if I could accomplish the same slight feathering of the butterflies in the venturi via the throttle cable (which has a little slack in it: should I take the slack out to assure I can get the full 120mph advertised top speed if I ever need it?). Is that another way to raise the idle or will I just create more problems doing that than it's worth in terms of being easier/more accessible? Someone said not to do that (open the butterflies via the throttle cable).

 

Yeah I'd leave the cable alone for now. The idle speed screw is the standard right tight/ left loose, and the idle will raise as you screw it in (right turn). It's a 4 barrel so there are 4 butterflies. Two on the primary throttle shaft and 2 on the secondary shaft.

 

OK, Bill and Ted's Excellent Idle Adventure is almost to an end.

With a little finessing around all the hosing, I can reach the idle screw using a 15" flat head screwdriver.

Now all I need is some guidance on which way to turn and by how much at a time.

I'm going to guess clockwise and a half turn to start.

Adjust once warmed up (magnetic choke released), right?

If I get this from 400 to 600rpm+, I am going to be a happy camper.

 

Sorry, I missed your post above before I posted my follow-on.

Will warm 'er up here this afternoon and see what happens.

Next on the agenda is renewing the dash (any suggestions other than "Just Dashes", which has gotten crazy expensive), some interior trim pieces (it's a maroon leather interior -- ugh, hard to find/match), a new power antenna (I bought one off this forum a while back but it didn't work, so I was wondering if someone could suggest a universal model that would fits with a little strapping bracket work?) and re-attach a rear defroster tab that's broken off.

With those fixes, it'll be a well-restored car in my "cars I always wanted as a teenager" collection. Just wish it got better gas mileage. With internal combustion engines there are three parameters to trade-off against: size/weight. performance and fuel economy. No ICE does all three well. The Wankel hits two-out-of-three: size/weight and performance. Freaking block is the size of a big toaster oven. As Mick said "you can't always get what you want".

Thanks for all the help. I'll do my best to pay-it-forward.

Oh, and the AC, forgot about that. When I first got the car I recharged it with R12a and it worked for a time, so guessing I have a leak somewhere. I certainly hope it doesn't have anything to do with the AC solenoid I understand from Haynes is in that vacuum-solenoid rack on the left side of the engine and seems pretty complicated.

 

If I'm not mistaken...if you close it all the way and then open it one and half turn.. that is the Mazda factory carb set up....

Start from there...or because you can actually run your motor start turning the idle/air screw or the linkage screw half a turn either way to see what it does....

I would start with the linkage screw to see first...

 

A small thing, but helps for the future. I painted the heads of the screws yellow, so they are easier to find the next time.