Tuning With An Air/Fuel Gauge

[madkaw]

You are also running vacuum advance and know it is working ? 

[chaseincats]

Just now, madkaw said:

You are also running vacuum advance and know it is working ? 

I'm pretty sure it's working - the vacuum bladder holds air and the plate is movable but I've never tested it with a vacuum pump.  That shouldn't affect idle richness though I'd think.

[madkaw]

2 minutes ago, chaseincats said:

I'm pretty sure it's working - the vacuum bladder holds air and the plate is movable but I've never tested it with a vacuum pump.  That shouldn't affect idle richness though I'd think.

It WOULD affect off cruise accel. Especially a lean mixture . You could try playing with ignition timing . The problem is if you raise idle timing it might add idle speed . 
if your engine has some miles on it you could advance valve timing to #2 . You would be surprised how it adds torque . 

[chaseincats]

1 minute ago, madkaw said:

It WOULD affect off cruise accel. Especially a lean mixture . You could try playing with ignition timing . The problem is if you raise idle timing it might add idle speed . 
if your engine has some miles on it you could advance valve timing to #2 . You would be surprised how it adds torque . 

I'd prefer not to mess with the distributor it is right bang on factory spec along with all the other sensors/contacts/valves etc (I went through the engine tuneup chapter of the FSM).

[madkaw]

I get it . But I would make sure all aspects of advance are in order . 

[Captain Obvious]

Hmmm... So you have the AFM gear adjusted such that cruise looks good (at 14.6), and WOT looks good (at low 13's), but idle is too lean at 16.5. And that's with the idle mixture screw turned all the way in.

Well first thought is vacuum leak, but you said you're good there. Second thought is throttle position switch, and you said you're good there too.

OK, so humor me since you got an A/F gauge... First thing, at idle, spray some starter fluid or carb cleaner in and around the intake tract while watching the A/F numbers. Make sure to hit the boot between the AFM and the throttle body, the throttle body butterfly shaft (both ends), and the BCDD area.

Something else to try... Unplug the TPS while watching the A/F. If the switch is being interpreted correctly, it should run even leaner with that switch disconnected. You can either disconnect it, or pop the black cover off and manually open the idle contacts. Gently.

And you can do the same sort of test for WOT... Drive the car around with the TPS disconnected and you should see your WOT numbers run leaner.

And you're sure you've got the altitude switch in the "richer" position, right?

Just tossing out ideas.

[chaseincats]

Ok, so update for you guys: I went to autozone and grabbed a handheld vacuum pressure tester and discovered that my carbon canister valve didn't hold vacuum and was creating a vacuum leak when the pedal was pressed (this is supposed to hold vacuum, right?).  So I disconnected the T-connector to the throttlebody and capped the hose port on the intake manifold and now I'm able to get to the 14s with a WAY leaner setting but the idle was still pretty lean up there.

I tried what @Captain Obvious was saying and started it then watched the gauge as I unplugged the TPS connector at idle and it did lean out, so that should be working.  I checked my altitude switch and that is set at off currently.

I've smoke tested the engine a few times so it shouldn't have any leaks in the AFM boot etc though.  The engine is warm now, so I'll wait until it cools off tomorrow to spray it with flammable chemicals lol.

It did occur to me that maybe the idle speed screw seal is worn down or something inside, is that a thing?  I have no idea how that looks internally.

 

EDIT: my impatience got the best of me so I grabbed a fire extinguisher and got spraying.  There MAY be a vacuum leak in the cold start injector inlet (I was messing with this recently).  Going to grab a pack of cigarettes and a pump BBL.

Edited March 8, 2021 by chaseincats

[chaseincats]

Looks like there's definitely egg on my face - I will be eating crow for dinner. @madkaw @Captain Obvious

There was indeed a non-trivial vacuum leak coming from the cold start valve's gasket.  Regarding the valve on the carbon canister, are those supposed to hold vacuum or are they a pass through because mine seems to bleed vacuum on this vacuum hand pump I got.

After covering the cold start valve inlet hole, the gauge's idle went from 17 to 13 immediately - I think we're onto something.

 

The cold start valve gasket had some bumps and unevenness to it which I sanded down and it still leaked after I screwed the bolts in with vigor, so it looks like I need a new one of those.  I don't understand how it was leaking though as there are no rips...

Edited March 8, 2021 by chaseincats

[madkaw]

 Leaking around the injector body itself ? Surface of mating surfaces were so rough that the dry seal wasn’t sealing ? 
vacuum leaks get everyone . You seem to know what your doing , so you keep pushing on . You might even get brave with timing 😉

[Captain Obvious]

Well that sounds promising! In my experience, I've never really liked that cold start seal in the first place.

It's on the high vacuum side.
It's a relatively thin, flimsy flange that is almost always bent from the force of the bolts that hold it down.
It's a high surface area to the number of bolts that hold it down, and those bolts are far from the center on those flimsy wings.

So if I had to have a cold start valve (which I'm not sure you do), I would slather that gasket up on both sides with silicone sealer. There's no way I would ever trust it put in completely dry.

But that aside... Being in Dallas, when do you ever, ever, ever get weather cold enough to even really need a cold start valve? It's not like you guys ever get temps below freezing, let alone into the 20's*. I've removed my cold start valve and capped off the hole and haven't looked back. I think you could do the same.

But (and I'm not judging) if you do want to keep it, for whatever reason, I would absolutely use some gasket sealer on that thing. If you got 13 with it blocked off, it's clear that if it's not leaking air, you're readings should be just about perfect.

And don't worry about the egg at all!

* Except for a week ago, right?    

[Captain Obvious]

And to answer some of the other questions...

The idle mixture screw is just a rounded nose fine pitch screw that bottoms out on a seat inside the AFM body. So I guess it could be possible for there to be crud built up down inside there that might prevent that screw from bottoming out completely? I do consider it a little unlikely though, because any crud inside there would probably be a soft carbon sticky mess of crankcase PCV blowby and would probably be smooshed by the screw tip and seal pretty well. I would consider it to be more likely that it would be to crud SHUT than crud open.

And about the carbon canister, to be honest, I'm not completely positive I understand the valve in that cap completely. I mean, the description in the FSM is pretty simple, and I understand how it is SUPPOSED to work, but after messing with that diaphragm and valve in the cap for the CARB can, I'm a little unsure.

I do know that the way it's SUPPOSED to work goes like this:

1) When the throttle is any position other than light cruise, everything is supposed to be shut-off and hold vacuum.
2) When the throttle is in light cruise, you should be able to draw a small amount of air through the larger vacuum line straight into the intake manifold. This is the purge cycle of the carbon canister.
3) The small control line is always vacuum sealed. You should be able to draw a small amount of air out of it with vacuum, but then it should always hold that vacuum.

The part I'm a little unclear on is the purge line... Looking at and playing with the valve in the CARB can cap, it seems like it's "normally open". But then the control line also pulls it open when you apply vacuum to the control?? So I'm thinking the manifold vacuum actually pulls the valve closed to seal it. And then the control line overcomes that vacuum and opens it again?

Does that make any sense or am I just making things worse?  

[chaseincats]

@madkaw It's strange because I used some light sandpaper and sanded both the intake and and cold start valve side a well as the gasket and it still didn't work.

@Captain Obvious The CSV definitely is used in the winter since I think it is triggered when the coolant is below just 50 degrees (even got a new one when mine died) lateron I wired it so that it triggers during each start regardless of outside temp because the car just starts so quick with it - very satisfying haha.  I later figured out though that if you are starting it before the engine has time to cool it basically floods the mixture and you will be stranded until the engine cools down (ask me how I know) so I undid that.

What do you mean by silicone sealer - do you mean RTV gasket marker?  I was going to head to autozone to grab some gasket paper and cut a new one, but you think a new dry gasket won't do much?