TR MONOSPECCHIO WITH IDLING PROBLEM

I think that you have an air leak on the inlet system somewhere. I would check that before anything else.
The auxiliary air valves can be checked by squeezing the pipe that feeds from the valve to the engine inlets. I.E. you close the air valve manually. Do this when the engine is warm. If it makes no difference it is not the auxiliary valves IMO.

Also there is a micro switch on the RHS throttle body. This sends a signal to the electronics to tell it that the throttle is at idle. In a QUIET garage with the engine off, move the throttle cable by hand (between the throttle bodies) slowly and listen for the slightest click from the micro switch. It should click just before the throttle hits the closed end stop.

There are some photos below of the parts that need checking.

I am sure that others will help out with other ideas zoo. Keep in touch with feedback.

P
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The (stock) F113A engine is K-Jet without Lambda so almost no electrical things to check or go wrong (which is a plus), but you have Warm-up Regulators (which is a minus ). Has your car been modified in any way for importation (you haven't given your location) -- i.e., did they add some sort of Lambda system?

The AAVs should be fully closed when the engine is warm, so, as a test, you can just physically block (or pinch closed) the air lines that pass thru the AAVs (simulating a properly closed warm AAV) -- if there is no change = AAVs are not the trouble; if there is a change = bad AAV. Same thing applies to the VLVs (vacuum limiting valves) -- they should be fully closed at idle, so blocking the air that might pass thru them simulates a properly closed VLV at idle.

Was the car running perfectly and this trouble just appeared suddenly, or was the car recently (mis)tweaked and it's never been OK since then?

If you can't find anything obviously wrong (broken hose, etc.) and the AAVs and VLVs seem properly closed at idle, the next diagnostic check IMO would be to measure the various fuel pressures on both banks: regulated supply pressure, cold control pressure, and warm control pressure. (But, if your system has been modified, that adds other variables).

 

And what about the VLVs?

 

The VLVs are not the easiest things to access on your F113A engine (since they are located under the intake plenums in front of the throttle bodies). There's one for each bank -- Items F as shown in the figure from your OM page 64:

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This is the description of their function from the TR WSM (where I've added some labels to the various ports on the device). Like the AAV, they let extra air into the engine under a certain condition (only under very high manifold vacuum during hard engine braking/deceleration), but they should be fully closed during normal warm idle. When you "blip" the throttle, you may be briefly activating them when vacuum level spikes up after the throttle plates are quickly closed -- so a faulty one could be sometimes not sealing and then sometimes sealing. When there is very high vacuum present on the small port #1 = the internal valve is open and air flows from port #2 to port #3 so extra air enter the engine (and "limits" the maximum vacuum level -- hence the name). When there is not a very high vacuum present on port #1 = the internal valve should be closed and no air flows from port #2 to port #3:

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I had a similar problem with my 1985 Euro TR.

When I started the car, the RPM's would oscellate at idle.
Sometimes it would settle down, other times, it would go higher and higher (1.5k to 500), and finally stall on the low side.
I also could drive 100 miles just fine, then when I came to the exit, the rpms would drop well below 1000 and I would sometimes stall.

I had the Warm up regulators rebuilt. (You can search the forum for the guy who does them, or PM me). It seemed to solve most of the problem. Then they did general tune-up things.

I am not knowledgeable as a mechanic, can only share my experience.

 

No, not really practical. Are you looking for F PN 117646 = Bosch 0280160138 (which is the correct VLV for a F113A euro TR) or F PN 115741 = Bosch 0280160111 (which is for a later F113B TR, but would probably work OK, and just has some extra bracketry)?

I realize this will add expense for you because of your location, but both RicambiAmerica (www.ricambiamerica.com) and All Ferrari Parts (www.allferrariparts.com) here in the US show these as being available.

 

since you have a boxer with carbs, and a carb 308, I know this will sond silly, but gret investment in a PAIR of fuel pressure guages, as they are really 2 six cyl engines in unison...despite all talk...treat as two sixes which must-MUST-be matched perfectly evenly...thus fuel pressure is important with NO lambda-this should be easy car to keep going for you with some basic guages and fittings. these other parts are almost NEVER bad, warm up regulators go bad on all cars , all the time, so you should ck this BEFORE spending hundreds of dollars on obscure parts which probably are ok....think carefully of valve function, think cause and effect...the odd valve STILL might be bad-but you should test baseline first-to be certain...
ciao!

 

Why is this a problem? The nominal warm idle spec is 1000 RPM (although the pressures inside each itake manifold plenum needs to be equal).

Sorry that you got misled on the VLV, but my suggestion was:

"Same thing applies to the VLVs (vacuum limiting valves) -- they should be fully closed at idle, so blocking the air that might pass thru them simulates a properly closed VLV at idle."

to see if it had an effect -- not just unplugging the vacuum input hose to see if that had an effect (but I should've pressed you harder on this point).

 

Thanks for the very kind words and the indulgence Marco.

One comment that I'd make here is that I found my tach gauge reads high -- when it shows 1000 RPM, the true engine RPM is ~860 RPM (so; consequently, it shows ~1150 RPM when the engine is really at 1000 RPM). Doesn't mean that all TR tachs read high, but you might want to check this point (if you are relying on the tach gauge for determining engine RPM). I use the frequency function on my multimeter and measure the RPM sensor signal (the TR flywheel with 146 teeth, or 146 cycles/rev, spinning at 1000 RPM produces a signal of 2433 Hz). Alternative, some (digital) timing lights have a pretty good/accurate RPM function.

If you unplug the vacuum hose going to the MicroPlex ignition ECU over the rear LH wheel, and doing that giving a smoother idle makes somewhat more sense. When you do that, not only are you letting a small amount of more air into the engine, but the idle timing will shift from 14 deg BTDC to 10 deg BTDC. I agree it is surprising that unplugging any other small vacuum hose would have such a seemingly large effect too, but, (if your tach reads high), you may be at a very low idle RPM so a little change makes a big effect. Opening the air bypass screws a little more should be identical to unplugging a vacuum hose, so upping the idle RPM to the nominal spec should provide the same benefit.

 

Have you changed your injectors to brass Bosch or you still have the original injectors? I did change mine to Bosch few months ago and it was money well spent. Est. $35-45 each.

 

Fantastic news Gian Marco !!

This forum is such a fabulous bonus to Ferrari ownership-lots of generous and very knowledgeable owners give of their time and effort so others may benefit

I am starting to perform checks and small "easy" jobs on my car -through the help of this forum. very satisfying !!

Tr boy