My 348 Stalls when in Neutral any Ideas

Thats tough. Im not a Ferrari tech, but I know a lot about engines.

I bet Riacambi (sp?) or No Doubt could help you pin point it. Could be air/fuel mixture, a sensor, throttle cable adjustment, IAC (if a 348 has one), could be electrical?

Check engine lights go on when this was happening?

 

I'm no technitian either, but that happend to me once about 3 weeks ago and then never again. I thought it was coincedence when I came to stopped pushed clutch at same time radiator fans came on. Maybe overwhelmed alternator? No check engine lights, started right back up, and ran fine after.

 

Sounds Familiar!
http://www.ferrarichat.com/forum/showthread.php?t=95323

The master tech Tom Jones from SportAuto.cc solved my problem.
Here are his instructions!
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Email 1
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adjust the air bypass screw shown. All you have to do is with a 14mm box end wrench, loosen the lock nut. Use a straight blade screwdriver, turn the screw out 1 complete turn then retighten the lock nut while holding the screw in place with the screwdriver. Do this to both throttle bodies.
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If that does not work.....(mine took email 2 to fix the problem)
email 2
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Turn the throttle body screws out one turn, shut off the battery for 1 minute, turn the battery back on, without touching the throttle start the car and let it idle for 15 minutes before driving again.


Let me know how it goes!
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Andrew; Has the battery been disconnected lately, or been run down enough that it needed a jump start? You may just need to "re-initialize" the ECU's.

 

What Jeff said, and on the above post about adjusting the bleed screws, when doing this you really need to balance the airflow between the banks not just turn screws in and out. Regards, Vern

 

You may have encountered some dirty fuel - Sydney is notorious for that. Try another servo and/or brand of petrol (I use Mobil Synergy).

 

My 348 does that about once every 6 months....and then never does it again! Haven't figured out either, but it has been a very long time since it has done it...Mine would do as I was coming to a stop.

 

Are you talking about #3 and #4 in this picture?
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It has to do with the air/fuel mixture. Thats what would cause a stall sometimes.
Could be a main relay ? or fuel relay too.

 

Yes, it's #3 and #4 in the picture. The most common cause of this problem is an imbalance in the idle air bypass (air bleed) adjustments between the banks. That is the purpose of this adjustment. I believe you need a manometer.

-Peter

 

Hi Peter, Yes, you should use a manometer to do it correctly there is a procedure in the shop manual on how to do it. Just a quick note there are 8 of those adjusting screws on the 355s, now that is entertaining same as balancing the Webers on older Ferraris although you do not have to worry about A/F mixture just balancing air flow. Regards, Vern

 

Thanks, Gentlemen. I bought one of these (pic below) manometers for $16...

Not entirely sure how to match up the two tubes/hoses with the 348's vacuum depression ports, though (adaptor??).
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You need to read the procedure in the shop manual there are some initial steps you do first and you should have two manometers one for each bank so you can watch them simultaneously. There is a procedure if you have reset the throttle plates to reset the throttle potentiometers also. If it runs fine now I woundn't mess with it.

 

It runs fine, so like you say I'm not going to mess with it...but eventually I suspect that I'll have to go there.

Two manometers surprises me, though. If you are measuring differential pressure, you'd just want one hose going to each bank (so 2 hoses would connect to 1 manometer)...when the red fluid is at the same level on both sides, then you have equal vacuums. Not complicated.

But if you use two manometers, then you've got to have them both perfectly calibrated, and with exactly the same lengths of connecting hoses. Much more complicated to get the same results, unless I'm missing something.

 

You can use one if you want but, you have to keep moving a single one back and forth and remembering what the reading was each time. I have found it easier to use two less jumping around. On the 355(eight indiviual throttle plates) and on a weber carbed(8 or 12 plates) engine it is just easier to use two. They are sort of self caibrated(lack of a better way to say it) the columns are the same size/volume if you want just attach them to the same side one after the other and see if you get the reading on both, you should, before you start any adjustments.

 

This is what Tim Stanford adjusted on my 348 when I had the same problem. He did not make that drastic of an adjustment however. We did three adjustements of 1/8 turn each until the stalling disappeared. About a year ago and no problems since. Tim stressed that it is very imp[ortant to adjust both sides identically. Good luck.
BT

 

Is this "air bypass screw" on each 348 throttle body known on other car models as the "idle air bypass screw?"

If so, it seems like a very reasonable/dependable fix (presuming both banks remain balanced) for stalls at idle.

 

Don't know the technical term for it but the mechanic said it adjusts the idle air mixture. He said it is a pretty common item to need adjustment after several years. My car got adjusted a total of 3/8 of a turn on both sides to get rid of the stalling.
BT

 

Not to split hairs Bill but, it is only idle *air* flow not mixture, there is no fuel adjustment with the screws. Oh and also on nd's post its one way to adjust idle you can also do it by tweaking the 2 throttle plates but that is a whole other story that is not as easy to do. Regards, Vern

 

"Is this "air bypass screw" on each 348 throttle body known on other car models as the "idle air bypass screw?""

That is correct. No effect on idle mixture, that is electronically controlled by the ECU's and the injector opening interval. Just adjusts idle air bypass around the throttle plates. That's why it's important to do both equally, otherwise everything goes cattywompus...

I love Tom, been a local colleague of his for twenty-five years, but one turn is an awful lot.

-Peter (been a colleague of Tim for years, too. That's what you get for going to Annual Meets and meeting these guys in the hotel bar. "Tech Sessions" Sort of like a "convention" for F-car techs <grin>)

 

Thank you!

 

On the early 348's, the bypass screws were completely shut and there was not enough air flow around the throttle plates therefore causing occasional stalling. To do this absolutely correct, you will need to block off the idle motors, not just disconnect them. Using the monometer hooked to both banks, you will open the bypass screws enough to set the idle to about 850 RPMs and watching that the banks are "balanced" i.e. drawing the same amount of air. To get it to idle this high without the idle motors active, you will need to turn the screws out a lot. After this procedure is completed, you will need to reconnect the idle motors, disconnect the battery for a short time, restart the car and allow the ECU's to relearn their parameters. On BT's car, when you are trying to fix it over the phone and you have done enough of these to know about what it takes to eliminate the problem, one can make an adjustment such as he did and not really worry about it affecting the running. It may not be perfectly balanced but it will probably be pretty close.

 

LOL!

I haven't heard that term in ages. That gave me a good chuckle.

 

I stand corrected, Tom. It was my understanding, just as it is with the idle air bypass screws on the 40 DCNF's on 308's and V-12's, that both screws start out closed and you open the one you need to equalize the banks (or both barrels on the carbs). Then, if you need to raise idle on the injected car, you unscrew BOTH an equal amount to keep the balance, or at least close to it. Thanks for clarifying that.

I'll slink back to flushing my clogged up expansion valve on Mary's t Coupe after I found that the drier dessicant bag exploded! Thanks for that tip, too.

-Peter (can't get away with anything around here! <grin>)