360 Starting ''issue''....

This is an interesting theory posted on another board:
"There are two brown micro-relays that power the engine control units. Sometimes they can become lazy and if one engages before the other it causes the communication line between the two units to become scrambled. One side of the engine effectively fires before the other and it will run like crap. Once the relays have operated once they are normally o.k, which is why it always runs fine on restart."

I've never heard that one before. Is there any validity to this? It actually makes a lot of sense, and may also describe why this issue is happening when the battery gets weak. I wonder if those of us that have had this issue should change these relays out? If so, Which ones are they, where are they?

 

Mine has acted strange a few times after filling up at the gas station, but not in a while. Idle going at strange rpms and stumbling.

I just occurred to me that it hasn't happened since I started using a battery tender. hhhmmmmm

 

That's another "common" problem or quirk.
After filling up, the car will idle rough after stopping at the first light (as long as it's within a mile or so). As it's driven you will not notice any drivability issues. After it has it's "episode" of roughness while stopped at the first light, it won't do it again until the next fill-up. If you continue driving for over a mile after filling up without stopping, you will never have the issue. Even during these "episodes", the car will always pull strong and rev smoothly.
I know at least 2 other owners that told me that their car does the same exact thing. Mine does it like clock work, EVERY time I fill up with gas. By the way, I have a brand new battery that's always on a tender.
At this point, I'm not worried about it at all, and I'll just call it another Ferrari-ism.

 

Does this mean battery tenders can also fix bad gas (besides keeping your battery charged)?

 

+1 on the Techron. Over the years this has happened at least 3 times maybe 4. After 1 full tank with Techron, each time the stumble stopped for 6-12 mos.

 

Kevin,

Ok, 2,600 miles in 6-7 months, not a garage queen! Put more miles in good health.

Btw, I pass by Walteria on weekends when I run my errands.

Aloha!

 

I am lucky I dont live on the mainland because I would rack up a ridiculous amount of miles if I was still there. Roadtrip anyone?

 

Along similar lines: After a complete power down, the 360 engine will run as described by the OP. The FWM (A3.28) mentions that the injector CU has to reset.

Specific to the OP's problem, my WAG is intermittent ground fault related to the ECU(s), while in open-loop mode.

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up4speed: The gas tank for communicates with the ECU via the gas tank pressure sensor (US cars).
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I have used Redline injector cleaner for years with great results...just fyi

 

It appears that you tried all of the basics...I'm very curious to hear what finally fixes your car. Please update us when you find it. I'm wondering if the info on the relays is the golden answer?

 

Interesting. So the relays they are suggestign are #55 (page 4.23 manual) behind the passenger seat and relay #88 behind the driver seat (page 4.26 manual). Perhaps give them a tap when the car is running if its a sticking contact issue..

Or.. swap them out with another identical relay and see if it stops..

 

As mentioned, the 360 will run badly for a short period of time after a complete power-down, while the injectors reset.

Since you observed no change in behavior after your power-down/restart, what do you think about the proposition that your injectors are always resetting? (More accurately: The injectors are resetting when the ECU is in open-loop mode.)

 

I don't know about injectors "resetting". They're a pretty dumb piece of equipment.

993T you might try using an IR thermometer to try and narrow down which cylinder(s) aren't firing correctly. Is it consistent I wonder? If you find one or two that are always cold you might pull the plugs when cold and see if wet.

BTW, I rarely wait for Check OK to light in the dash and I reckon it makes absolutely no difference.

 

I can't claim any particular expertise or talent in this area, so I'll have to say that your guess is as good as (or better) than mine.



Actually, my only real talent is appreciated by a fairly small group (good looking women between the ages of 18 and 35)...but, I digress.

The workshop manual (A3.28) talks about injectors resetting on power-down.



The thing that is interesting (about the OP's problem) is that there are no error codes. If the engine were actually running on 4 cylinders, I'm thinking that the ECU would store codes.


As mentioned, my WAG is ground fault, but the relay theory sounds interesting. If the relays cause the ECU to lose potential, it would clear all codes and reset the injectors.

(On some cars, like Toyota, the ECU would still have power even with the relays completely removed. I don't have a diagram for the Ferrari ECU.)


I've uploaded pictures of the power relays; they are marked (2) in the illustrations (ref: FWM C3.08)
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Excellent info. I am learning a lot.

Thanks Steve.

Dan

 

Yeah, agree with Greg, the injectors spray upon command from the ECUs without any intelligence... Fuel pressure at the rail and the ECU opens/closes them to inject fuel.

 

Maybe I'm misinterpreting the section below from the FWM (wouldn't be the first time):
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I guess we're talking about the ECUs which control the injection (and multiple other bits and bobs) resetting. Yes, they reset to a base map when powered down. They certainly "shouldn't" reset every time the car is turned off but obviously anything is possible.

If one uses an IR thermometer one should be able to establish whether an entire bank is slow to wake up and get going or, more likely I suspect, a single cylinder or two. If it's an entire bank then one's attention might reasonably turn to the ECU for that bank (and any other components that relate to an entire bank) but if only a cylinder or two is misbehaving it's more likely to be injectors, inlet gasket, faulty plug/lead/coil.

 

My interpretation is that the ECU goes into "self learning mode" upon restart, after an event where no potential exists across the ECU.


The Toyota schematic below illustrates that the ECU still sees battery potential, regardless of whether the ignition switch is open or closed. (I added the red text.)

I suspect that the 360 ECU is somewhat similar, but instead of a fuse, it employs a battery shut-off switch.


My guess is that while the engine runs with the ECU in "self learning mode," all cylinders are operating; however, the injection time (tj in the equation posted above) is being "tuned-in."
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What is the left rail and right rail fuel pressure when running on ONLY 4?