Whats the throttle plate gap?

Technically, throttle set screws should never be touched which is why they are tamper proofed before leaving the factory. The need to make an adjustment is indicative of something else going on in the system whether you're trying to reduce idle (leak downstream of throttle) or increase idle (coked up bore AND IACV not compensating correctly). By your description, it sounds like you have a leak in the system.

Anyway, all I can do is to provide you some background to how Throttle Blades are typically set in a production environment.

There are two main methods:

1. The blades are set to a predetermined angle so as not to bind with the bore in the worst case condition.......plus some factor of safety. Worst case would be at extreme tolerance limits and low temperatures due to thermal contraction. I say contraction rather than expansion because we have Aluminum Housings and Brass blades but this dos not help you because you don't have precise Bore ID and Blade OD dimensions. Even if you did have this specified angle, it would still be difficult to reference an external datum surface to establish this angle (also referred to as "idle angle" or LMS which stands for Lower Mechanical Stop).

2. Alternatively, the Blades are set with airflow (volumetric or mass flow rate) at a prescribed delta pressure and compensated for at STP. This method is forgiving of tolerances but it is a time and capital intensive process and requires multiple iterations before it stabilizes.

There is another way which utilizes the TPS (Throttle Position Sensor) but this is by no means a production method because the TPS has its own set of variation. Unfortunately, our TPS's are more like discrete on/off switches rather than variable potentiometer outputs so I doubt this helps either.

The point is that Blades are never set to a gap. Sorry I can't help you with an exact setting dimension or procedure but I'm sure others around here have encountered the same issue and found a solution around it. Good luck.

 

to make a basic setting I always close the trottle plate completely and then turn the adjusting srew so far in, that the plate just starts to move, but even only a little bit. this prevents the plate touching the aluminum and after a while will get damaged.
so I do on all cars with K and KE jetronic

 

Plate adjustment screws are sealed to comply with Federal law. It has nothing to do or not to do with what should be done.




The air bleed screws should be totally closed, plate adjustment screws set at 750 rpm with o2 sensors disconnected and mixtures at 1%-1.5% and equal vacuum on both sides. Using air bleed screws set idle at 1100 A/C and rad fans off, mixtures still at 1-1.5% and vacuum equal. Reconnect O2's reset idle with air bleeds to 1100 a/c and rad fans off and check to see if mixture came down to about .6% and about 125-150HC.

 

In all my years, and it's coming on 20 years now, of designing, testing, manufacturing and selling both Mechanical and Electronic Throttle Bodies with 10's of millions sold (including Ferrari), I have yet to hear that "idle adjustment screws" are meant to be adjusted. In the past, I applied paint on the set screw for protection against tampering for reasons I've mentioned above, not because the government mandated it. With modern day Electronic Throttle Bodies (ETB, ETC or "Drive by Wire" as it is commonly known), I don't even give the option. Why?, because the Engine Management System is self correcting unlike Carbureted systems. The Testerossa Air/Fuel Management System with its Mechanical Throttle Bodies has an Idle Air Control Value (IACV) to make up the difference and maintain steady idle amongst other reasons not relevant to the topic.

Again, and only my opinion in regard to airflow:
- For high idle, check for downstream leaks or inadequate IACV sealing.
- For Low Idle, check inadequate IACV travel or response.

Now I'm not saying you're doing anything wrong, just saying that OEM's don't recommend adjusting it hence tamper proofing paint. I'm also not aware what Ferrari specifically mentions in this particular system but I'd be very surprised if they recommend making adjustments to the set screw, but then again, who knows.....

 

No, no IACV on a TR (that was introduced with Motronic on 512TR). There is an anti-tamper plastic cap that snaps onto the throttle plate adjustment screw to prevent someone from rotating it after factory adjustment (and I think Brian is right that that was mandated by the US gov), but I'd also agree with your point that, in theory, one shouldn't have to readjust them (but I wonder how many TR still have them in place -- a sick TR often gets molested in places that it shouldn't be touched ).

 

Isn't there an air bypass valve on Testarossa's?

 

Yes, there are air bypass valves, but they are not controlled by an electrical signal (nor called IACVs) - it's just a "set-to-one-location" manual mechanical adjustment.

 

Often not set well at the factory and as you said, many reset afterward.

In 1980 USEPA mandated adjustments that could effect mixtures needed to be sealed. The CIS throttle plate adjustment has mixture influence so they were sealed just as the actual mixture screw was sealed.

 

If they were not meant to be adjusted Ferrari and Bosch would not have provided instructions for the proper method to do so and provided the seals to replace the originals when done.

IACV?

Wrong generation of car.

Who knows??? I do.

 

Interesting. There looks to be two components that "resemble" bypass airflow valves. 9 (41) bypasses the Blade and looks like the mechanical valve you're referring to (no pin outs) but 13 (31) looks to be some sort of spring loaded pulse activated electric valve (2 pin). What are these used for?

I'm sure you're right here. Just saying that in my experience, and I will admit I started way after Bosch CIS, Idle Air at the Throttle Plate was never meant to be an adjustable feature.

PS. I use the term "IACV " generically, i.e. a valve used to adjust/stabilize Idle Air in a closed loop system.

Thanks for the heads up.

EDIT:
My comments are certainly confounding the issue the OP is trying to resolve. Please ignore them and stick to the advice from those intermit with these cars namely, Ramano, Steve and Brian
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9/41 is the vacuum limiting valve (VLV) -- it opens under the condition of high intake manifold vacuum (hard engine deceleration) to prevent the system from going too lean when in that condition (i.e. it lets extra air bypass the throttle plate to keep the airflow metering plate deflected = keeps the slits more open = adds fuel). During normal running/idle, it is fully closed. It is only used on the non-Lambda TRs (F113A/F113B) -- on the US TR, they use the EHA to directly add extra fuel to prevent the over-leanness from occurring in that condition.

13/31 is the auxiliary air valve (AAV) -- it is only open at cold start-up. It is a thermo-mechanical device that closes as things heat-up. It too is fully closed during normal warm running/warm idle. The electrical connection is just a constant +12V and ground to run an internal electric heater (no intelligence/no control). All TR have these.

 

Thanks Steve.

 

F PN 115741 = Bosch 0280160111

This is more a result of the imbalance -- not the cause. Once you correct the intake pressure imbalance between the two banks, the deflections of the air metering plates (at idle) will be more equal.

 

there are 4 possibilities:

1st: on this side where tjhe plate is not as wide open as on the other side the system sucks wrong air somewhere

2nd: the mechanism ot the side where the plate is not as wide open is blocked somewhere or sluggishly

3rd: the trottle plates are not correct

4th: the automatic idle valve is not working right


best would be take a vacuum meter and meassure both sides, then you can see how to go on
good luck and keep us informed

 

I just am recovering from this exercise of throttle plate position, and how to set. Brian and Larry were very helpful and patient trying to explain how to sort out. Based on what was tripping me up, the best input I can give is use vacuum to set, and it must be very sensitive with good resolution. Ferrari suggests mercury manometers, and setting within 5mm. I was trying to get this resolution from two hi quality large vacuum process gauges. The friction, and imbalance between these gages made them worthless. Not to mention they had scale increments of .25 inches or 6.35mm which is already greater than what Ferrari wants.

It may sound silly, but I went to youtube, and looked up the clever water manometers folks set up for motorcycles. The resolution is ~13.6 X better than mercury (based on density). Do not use a setup that will allow water, or whatever fluid used to get into the engine. Incredible that when I first connected this contraption I assembled from glass Italian made olive oil bottles, it showed a large imbalance not seen on my other mechanical gauges. I acted on the bypass screws to do the final setting, and AFR / CO / HC finally settled down. What a huge relief! It really transformed what was my tuning disaster after touching the throttle plate screws. The starting point for the throttle plates was a very carefully positioned piece of paper ~1/2" wide placed in the same spots on both plates, and taking care to sense the force required to slide the paper. Viewing the throttle plate was done with a fiberscope, and I held the paper with a small clip on a piece of copper wire.

Best of luck!

I learned my lesson to never touch those throttle plate setting screws!

 

When was it last running correctly? This was the biggest clue which helped me get past the big questions I was asked: Cam timing? / bad valve? / bad cylinder? etc etc. Nothing occurred that would have wrecked the motor, but now she runs awful! It ran perfect until I did an oil change, and unknowingly knocked off a vacuum line, then proceeded to un-tune everything before I noticed the dumb hose hidden from view. I only discovered it by trying to connect a vac gauge to it. I then systematically started checking every hose which were pretty fresh from recent EO service over and over wasting a lot of time, fuel and patience. It really sounds like you're chasing the same demons I was trying to find. And "accurate enough" really wasn't for me. It surprised me too. Again, I bought these nice large 8 1/2" dial vacuum process gauges, and they stuck the tiniest bit, which was enough that I could never measure within 5mm Hg. Beauty of a manometer is they don't stick.

BTW: I have those Innovate LM2 gadget's but never took them out of the box. Do you like them? I use an IR Industries FGA4000XDS exhaust gas analyzer for lambda & air/fuel ratio measurements. I think this is a great piece of equipment. Best car gizmo I've used. A little pricey, but I have good confidence in it's performance. Life saver for strict SMOG testing requirements.

Hope you solve it quickly. Please let us know what you discover.