Erratic idle- Mondial QV

I have an erratic idle, especially when cold. It does not do it all of the time. Below is a video link:

https://youtu.be/SdKQGdDbA0w

Any ideas?

 

Seeing how it seemed to stop after you tapped the throttle, my guess is the throttle position sensor either needs adjustment or has failed and is giving incorrect resistance signals. The surging is the computer somehow getting wrong signals, richening the mixture, overcompensating and than adjusting back.

I recall someone had low coolant and air in the coolant, which can give some odd readings when the computer is measuring coolant temps, so might be worth checking/bleeding, can"t do any harm!

 

I know the TPS switch was replaced recently, and new coolant was installed this spring.

Isn't there a crank sensor as well?

 

Is yours a 3.0 liter? If so then you have 3 crank sensors .... If 3.2 then only two. However, your idle is erratic on the high side which leads me to think the problem is with the FI... Warm up regulator perhaps or maybe the air flow sensor plate is not properly centered and is hanging up until you blip the throttle??

Brock

 

Maybe the cold start injector is leaking. Try removing it, and cover the hole with duct tape.

 

First things first, you need to look at the spark. I have a similar problem which when I get time I will fix.
Here is my diagnosis, it took me about 20 mins to track down the problem to a spark timing issue at idle.

https://www.youtube.com/watch?v=lX0vwhlDSVE&feature=youtu.be

1.Get a strobe light
2.Mark your crank damper with a white maker at TDC on piston 1 and TDC on piston 5.
3.Measure as I have in the video.
4. If all is as it should be then it's fuel.
Good luck, Bell bloke.

 

Check the run of the throttle cable as it can foul the carpet , if no better try some redex or similar injector cleaner in the tank

 

Mine is a 308 QV.

Warm up regulator was also replaced with a rebuilt unit a couple of years ago. This erratic idle also occurs when driving and engine is warm. So, it is not limited to when engine is cold or at startup.

 

Ok, being a 3.0 liter that means you have three sensors...so to Bell Blokes' point, let me ask this question as it was difficult to hear the engine running in your video.....When your tachometer indicates erratic rpm you can hear the engine revs fluctuate too, correct? And the erratic idle revs are higher than the normal idle speed, yes?

 

Well I took the Mondial in for service. The erratic idle mirrored the engine RPM as well. So, the engine RPM did fluctuate like the tachometer.

We initially thought it may be the crank sensors, but the three sensors checked out OK. My mechanic checked out one of the distributor caps, and the rotor was not properly installed, and there was moisture in the cap. So, we replaced the rotor, cap, and spark plug wires. This appears to have fixed the problem. No erratic idle so far.

One thing about Ferraris. You can spend a lot of time replacing parts that don't fix the problem. And even supposed Ferrari shops don't get it right. I have spent a lot of money on repairs and mechanics who made repairs, and I have had to pay other mechanics to fix what they sometimes could not repair. Sometimes, they also did not repair properly. For example, I paid to repair shift shaft seal and new oil pan gaskets. The mechanic did not use the right sealant, and the oil pan gaskets are leaking again. Will have to pay to redo this job but will wait until next year.

 

Excellent, it sounds like it was a relatively easy repair....good to hear what the problem was!

Brock