Engine revs holding

A lot cleaner than my old mondial was, never had the engine out of mine in 20 years ownership

 

Found this thread
https://www.ferrarichat.com/forum/threads/throttle-position-switch-308-qv-question.159111/

So it's got one on there.. not sure of the position though.

 

Not great, but:

If the O2 sensor is unplugged/missing, the frequency valve would still be buzzing if the added injection ECU is still powered up, wired, and working. If the system is tweaked-up warm in this condition, it would still work OKish as a K-Jet without Lambda during both warm-running and cold-running (but should really have the VLV reinstated).

If the O2 sensor is unplugged/missing and the injection ECU is disconnected, the frequency valve will not buzz (and just remain always closed). If the system is tweaked-up warm in this condition, it should run reasonably well when warm as a K-Jet without Lambda, but cold-running will be lean (and it should really have the VLV reinstated). For cold-running to work well, it would have to be tweaked-up "rich" -- might have been done intentionally for this reason (but, being K-Jet without Lambda, the WUR control pressure being wacko can also cause this).

Physically removing the cold start injector (blocking the air hole in the plenum) and seeing what comes out the end (into a container) is best as this detects both mechanical and electrical problems with the cold start injector; whereas, unplugging the cold start injector only prevents electrical problems from wrongly causing it to squirt. It may still squirt a little at warm restart cranking, but should definitely be fully closed during warm idle.

 

Could be. There's quite a bit of wiggle room in the motor mount holes. I think it's would be pretty easy to have the engine land 1/4" different when installed but that dog bone is a fixed length. And moving it wouldn't affect the throttle cable operation or position. Heck, it moves more than that under acceleration.

 

In the USA '83 QVs don't, '85s do, and I think '84s do. I think the switch shows up with lambda control.

The car in question doesn't. If it should or not, I don't know. It's got a gray market mish-mash going on.

 

It's the throttle bypass, it adjusts your idle speed. Wouldn't cause the issue you are having.

 

Earlier in the year I worked on a EU 308QV converted to US with this exact problem. Many things were inspected and tried, in the end adjusting the idle speed and mixture at the fuel distributor solved the problem.

 

Just touch it while the engine is running -- you should feel it vibrating if it is working.

To back up some -- was the engine running well before all this? Is the air bypass screw the only thing (affecting the airflow and mixture) that was messed with?

 

The engine was running well before he decided to clean and rebuild every CIS components he could see.

 

Sure, the voltage between the two pins of the connector for the WUR should be +12V whenever the engine is running.

 

Before you cleaned everything including the injectors, your car was adjusted to deal with all the imperfection of the CIS system components. Now that you have cleaned everything, the combination of the setting is off and you have to re-adjust the idle speed, and the mixture to bring it back to optimal. On a US car with an O2 sensor, you can hook up a scope to the O2 sensor signal and adjust the mixture for 50% duty cycle. On a Euro car with no O2 sensor, you will have to wing it.

On the car I worked on, some imperfect idle condition existed before I did a major service with all the timing belts, plugs, etc, and then I cleaned the throttle housing and a few other things. Since there was so much work done, I needed to reset the CIS pressure settings, the idle speed, and the mixture. The Euro car was more involved because there was no idle switch to tell the CPU ... "i'm at idle, or not"

 

This is why checking/verifying the cold and warm control pressures of the WUR is a must before tweaking the mixture screw (and airflow screws).

 

One part worth checking is the bypass valve (81). If it leaks internally, it gives exactly the same symptoms. It is easy to check by clamping the hose(s) and see if the idle returns to normal. Image Unavailable, Please Login

 

I agree the vacuum limiting valve (VLV) would be a suspect for this symptom, I don't see that he has one. I certainly don't see one where it is on my USA '83 QV. I don't see any intake hoses that indicate it would be hidden away. But it could be somewhere not obvious in the engine photo.

 

He does not have one. It would be to the right of the throttle housing but they removed it for the last years of the 308QV EU.

 

Did the car ever have any backfires at some point? If so check the fuel dist sensor plate for flatness, mi 308 only idled at high rpm when warm and this was part of the problem.