Okay. The Jag is running quite nicely. Very happy so far (though I know I've peppered the forum here with a TON of questions - and thanks for the excellent replies!!)

I've also done a *lot* of searching, reading and then gone back to tinker. But so far, I haven't found the correct sequence of steps to start with a good-running system and take it to "just right". At the moment, I have new ignition wires on order and will (when those arrive) take out the plugs, clean & re-gap, check the rotor, etc. However, as I said right now she runs very nicely - although my idle speed seems high: about 1000 rpm.

Here's what I've done so far:

I've set the butterfly valves (0.002") with the engine off, using the small posts/lock nut on the throttle body.

I've tried to take up any of the slack in the throttle linkages. It idles very nicely (no loping). I *think* I'm looking for about 700 - 900 rpm at idle/NOT.

I tested the AAV per other posts, and with the engine, hot blocking the opening in the air filter housing has virtually NO impact on idle speed (therefore, the AAV is okay, right??)

However, at the same time, when I turn the nut on the AAV clockwise, I am having NO impact on idle speed either. My understanding was that this nut is used to adjust the hot idle and "...can take the idle right down to 400rpm". So does that mean the AAV is bad after all, or am I turning it the wrong direction??

Thanks!!

Brad

 

Thanks to Grant,,, and doing my own AAV dissection and rebuild (which included crushing the bulb to get the wax expansion adequate to seal the AAV) when the car is hot will have an effect on the idle speed... Small but fine tune...

What I learned on cracking the AAV and pulling out the guts was that due to years of airflow thru the AAV it had become sufficiently gummed up so that a smooth travel if the internal cylinder, to what is essentially closed, was not possible... Opening the AAV and resealing (then crushing down the bulb) made it operable.

I personally don't like the AAV and have since (during the summer months/I don't know about winter yet) blocked the opening in the air cleaner area. I could be all kinds ah wrong in doing that. But it's what I did...

 

MMMMMMM

3rd straight coffee, and I am concerned here.

With the engine AT operating temp, the internal piston is closed 100%.

BUT

The "by pass" passage cast into the AAV is ALWAYS open, and its this "by pass" passage that houses the Idle Bolt.

IF you are plugging the hole AT the air cleaner and nothing much happens, YOU HAVE A VAC LEAK SOMEWHERE. 1991 will NOT have the elbow in the Intake hose of the AAV, so you cannot blame that.

Plugging that hole at the air cleaner starves the AAV for Inlet air, and stalls the engine, fact, IF everything else as it should be.

Starting point for me would be:

1 slab of beer, any brand will so.
AAV needs to come off and be checked for proper operation.
ALL the vac hose need to be sprayed with Ether, engine running of course, to establish a leak or not.
Inlet manifold gaskets leak, so CAREFULLY tighten the 24 nuts that secure both manifolds to the heads.
Over run valves leak, you may NOT have them, so panic not. They are under the alloy domes at the front of each Inlet manifold IF you have them.

 

Damn!

If plugging that 90degree hose that comes off of the air cleaner will stall the engine,,, I'm in trouble. I unplugged the hose at operating temp and I had a small pull of air going in. Could feel it... Plug it with my thumb and the engine slows, no doubt, but not stalls!!! Hmmm... To about 800 to 825 rpms, obstructed,,, in park,,, about 900 unobstructed,,, in park...

And here I thought I was getting some where.

 

You are JJJ, you are. Your test proves the AAV is working as intended. The fact the engine does not stall is because a tiny bit of air is getting into the manifolds elsewhere. Tickover should be 650 rpm in gear, 750 in neutral, so maybe your butterflies are a bit over gapped, maybe the manifold nuts need a tighten etc etc. Do not fret, get the things you are working on done, say I, before getting distracted on relatively minor matters.
As to pipe tobacco. my Dad always smoked Gold Block, no idea if it exists now, or in the USA!

 

My understanding and experience is that if, every is as it should be, plugging-off the big inlet to the AAV will allow the engine to idle very low (400 rpm or so, as mentioned earlier, sounds right) thanks to the air coming in thru the .002" clearance at the throttle blades. Then, to get the idle to the desired 650-900 rpm (whatever suits your fancy) you use the adjustment at the AAV to admit more air. So, in a manner of speaking, the throttle openings provide a base idle speed and the AAV adjustment provides the desired idle speed.

Yes?

If the AAV adjustment bolt has no effect then A) you have more air coming in from elsewhere that is beyond the control range of the AAV adjustment or B) a mechanical difficulty hold the throttle slightly open. Or....maybe the air passageway at the adjustment bolt is clogged?

Cheers
DD

 

Ok. I'm on it...
I will have time to work on machines alllllll weekend.
My lady is mad at me...lol

Thank y'all so much! Really

 

Doug,

YOU ARE RIGHT, I had a BRAIN FADE, and apologise to the Forums for that.

YES

My V12 cars all run NO:

AAV
Balance pipe
PCV system
Cold start injectors
Over-run valves
NO emissions stuff at all.

AND

When I started the HE after all that removal, it did indeed idle at 400RPM +/-, so I adjusted the throttle bodies with a Carby Balancer, until I got the 750 I wanted.

The "Goose", some of you know of Clarke's new toy, stalled when that pipe was plugged, but it had other issues, like so many V12's, and once they were sorted, it also dropped to 450RPM when plugged.

 

Important and combined,,, with GiF,,, Doug and Grants info here,,, what I need to go and MAYBE get mine right.

I messed with the ECU pot a LONG time ago and I'm sure that's not right!

I was in there the other day and I don't like the PVC valve. In my 1990, honestly, I don't know what else in Grants list I do or don't have for emissions controls. Mine is NOT idling right, or cleanly, and does NOT go to 400-450 when I plug the large AAV elbow. I can NOT fine tune idle at AAV,,, it is closed all the way down. I don't like it.

A long time ago, one of the first things I did was remove the air pump rail and sealed ports into the intake. I need to check those. Thanks to Grants write up in adjusting throttle bodies and links, a LONG time ago, I did my best to adjust throttle bodies. I will need to recheck this, now.

I am so unfamiliar with the car in terms of difference in MY, body type, engine systems (which is sad at this point) that with a Marelli ignition, I don't even know what of the emission controls Grant mentioned above, I have, or don't have, on my 1990 car 😔

I have a lot to learn.

I really believe I need new 02 sensors. Although my "ABS" light is on, I really believe it to be my 02Sensor light (mixed up dummy lights in changing clusters trying to repair speedO).

I was driving in the car with my girl the other day with the hood up (first time driving with hood up) in traffic and the exhaust was making it into the car (thru windows I think) and was rich, heavy, thick... Seems way rich.

I have a waaaays to go before having things "right". I will be need y'all's help.

Still driving and enjoying her tho,,, FINALLY. Brake fluid leak and all else,,, lololol... I just gotta!

 

I am at about 650-680 in gear, flat. And about 900 in park or neutral... I don't think I have any control over idle with the idle bolt on the side of the AAV when I don't have it completely plugged...

I guess I plugged it a ways back to cease that high start up idle speed when it's wide open at start. Didn't feel like I needed it in the summer as a "choke" and didn't feel right about the engine speed at start up for fear of not enough oil in important areas of the engine so quickly while engine idle was so high, at start up. 1200 + or - rpms. Seemed like to much and she started fine without AAV. Wonder if that will be true in the winter months...?

 

Say no more!

Learning to trust ya, G...lol Got some on the way.

 

Hi

After making sure my AAV was OK and throttle gaps correct, I simply blocked all vacuum lines and other sources for air to the plenums, and I then ended out with 400-450 RPM idle with closed AAV idle adjustment screw.

For me the main source of bypass air was the engine breather check valve placed at LH air box at front end at the inside. I took it apart and placed some washers behind the spring to make it open at a higher differential pressure, assembled it using a few spot welds, and then my idle was good after opening the AAV adjustment screw a bit.

 

Hi Leo.
The breather check... Are you talking about the one that is associated with the AC system. The one that opens for extra air that increases idle when the AC is in operation? Or, something else?

 

No, the one you refer to is on RH side and is a solenoid. This is close to same position, just on LH side.
It is connected to the metal tube running over the injector tubing on top of everything

Leo

 

Sorry, got you. It happens sometimes,,, that sec when talking car, and I space on the LH RH side idea... thanks

Ok, there I have (I think) a PVC valve and it fits into a rubberized hole. The other day I pulled the PVC valve out of the hole (if that's what we are talking about) and it started taking more air, idle changed. I plugged PVC with thumb and idle smoothed. I don't like the PVC - I did replace it early on and now, I don't know WHAT to do with it... I just read Grant saybhe did away with it completely. More, I think a few vac lines are sharing that breather port. All need a good figuring out on my 1990.

 

Leo
That sounds like the PCV system to me.

 

PCV sounds familiar. It provides crankcase ventilation, so much I know, and I also know disconnecting it made my idle drop 150-200 RPM, so I modified it...