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Discussion Starter · #1 ·
My 91 348 is intermitantly dro

My 91 348 is intermitantly dropping bank 5/8. I've swapped all sensors to the 1/4 side, cleaned all connectors but the problem still exists. I think the next step would be to attack the wiring harness leading to the crank sensor. Is there an easier way to track it down without removing the motor to expose the harness? Can anyone tell me how to get hold of a wiring diagram to try and track this problem. Any and all info will be greatly appreaciated.
 
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Discussion Starter · #2 ·
If the "slow down 5-8"

If the "slow down 5-8" light is being illuminated you may be suffering from an exhaust computer failure or the thermocouples after the cat have gone south.
 
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Discussion Starter · #3 ·
Theusual test is to move the e

Theusual test is to move the exhaust ECU from the offending 5/8 side over to the 1/4 side. Once done, you look to see if the SLOW DOWN light switches from 5/8 over to 1/4.

If yes, the light switches, then the problem is typcially a failed exhaust ecu.

If no, the light still says SLOW DOWN 5/8, then you probablyhave a real problem such as an overheated cat that could catch fire and burn down your car and kill you and your passenger.

Is your cat on the 5/8 side glowing a dim red after a drive?

Also, check here for more SLOW DOWN info and tests: The348.com .
 
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Discussion Starter · #4 ·
Actually it's a lot easier

Actually it's a lot easier to just unplug the Cat ECU's and see if the "slow down" light goes off. However, if the light is coming on & it's not cutting out one bank of cylinders, then the problem lies elsewhere.
 
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Discussion Starter · #6 ·
Well since you are running pip

Well since you are running pipe and the cat ecu's are 86'd then here is what I would check.

1)Pull the ecu codes from both sides.

2)Condition of the spark plugs, and spark plug wires

3)Make sure that the Mass Air Flow Sensors are clean, that the connections are clean, and that the wires are in good condition under the rubber boots.

4)Make sure all your ground wires are connected properly

5)The condition of the wires under the rubber boots behind the connectors for the crank sensors, and make sure they are connected properly

6)The condition of the connections for the fuel rails. Those are located up under the intake plenum. You can see them on either side of the oil filter.

7)When was the last time you changed the fuel filters? If it has been a while you may want to give that a looksy.

Try those for now.
 
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Discussion Starter · #7 ·
The codes he is getting is for

The codes he is getting is for the RPM sensor, plugs and wires have checked out ok, mass air flows are good and switching from side to side does not move the problem, all connections should be clean , they were cleaned in Jan when I owned the car and had the major done, the fuel rails are fine I had them off then and the injectors cleaned then also, the fuel filters were replaced in Jan. The shop is telling Tim that the car is losing electrical power to the 5/8 ECU they advised him to replace the fuse panel but when he removed the panel he did not see any burned spots
 
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Discussion Starter · #8 ·
He DOES NOT need to replace th

He DOES NOT need to replace the fuse pannel.

Have him swap the crank sensors. They can be swapped in the same amount of time it took to swap the cat ecu's. Try that and see what that does. Make sure that the Motronic ecu's behind the seats are properly bolted to the body. The screws help to ground the ecu's. There are two screw for each ecu, with located one on top and one on the bottom. He can also swap the ecu's from side to side and see if that helps with the problem. He could have a bad ground issue with the Motronics that is causing him to get the CELs.

As for checking the wires, I mean the ones that are at the back of the connector, under the rubber boot, on the wiring loom side, not the wire on the sensor. You have to peal the boot back in order to see the wires. If you have a buddy with a running 348 you can borrow his cps's and see if that gets rid of the cel's. All you have to do is get the car up in the air enough so you can slide under it. The wiring loom connectors are right there.

If, and I mean IIIFFFFF, there is a problem with the fuse pannel, he should take it out, and apart, then clean it up. But I SERIOUSLY DOUBT that there is a problem with the fuse pannel. Again IF there is, it could be that there is a blow fuse or a bad relay that is an easy fix. There is NO need to replace the entire fuse pannel. So check out the fuses and relay that are in the kick pannel.

Better yet just take it to another shop. I don't like the sound of what these guys are saying. You don't solve a problem by throwing parts at it. You find THE problem and then fix THE problem.
 
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Discussion Starter · #9 ·
The Motronic has 2 relays per

The Motronic has 2 relays per side. Cheap standard parts, no Ferrari special, don’t have to be Bosch. Replace all 4 of them. You don’t loose to much money if they are not the cause.
 
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Discussion Starter · #10 ·
I just spoke with Tim and he h

I just spoke with Tim and he has changed the crank sensors and swapped the relays the problem is still there.
 
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Discussion Starter · #11 ·
Did....he....check....the....c

Did....he....check....the....condition....of....the....wires....behind....the....boot????????

How about the connections on the MAFS?

or

The spark plug wires?
 
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Discussion Starter · #12 ·
Seems to me someone is saying

Seems to me someone is saying to quick: We have done all this and all that.
I would start again from the beginning and ignore the exclusions made by others.
Sorry, but these Motronic´s don’t really have mysteries. You have all parts, except the phase sensor at the cam, right there in the engine bay for a left right exchange test. If its not the parts, it’s the wires. Try to find a general rule when the fault appears.

Some ideas that might help:

If it seems the power to the Motronic is lost, make a temporary bridge wire from the other ECU. The fault should disappear.

Make a copy double sized copy of the ECU´s wiring diagram and mark all important wires. Left and right ECU with different colours. Helps you to track down the fault.
 
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Discussion Starter · #13 ·
Hey guys, thanks for all of th

Hey guys, thanks for all of the info and the help. The problem is that,the relays for the 5/8 fuel pump and the relay for the injectors are tripping and intermittenly dropping power. Here is what has been done to the car. Just as Frank said, the car had the major service completed in January. The cats have been removed and replaced with pipes. All cat connections have been unplugged. I've removed the MAF'S, cleaned them, swapped them over and tie wrapped the connectors. The ECU'S have been swapped and the connectors have been cleaned. The crank sensors have been replaced and the connectors have been cleaned. The coils were swapped and plug wire boots were cleaned. The fuse panel was removed and checked, but no solder or power problems detected. We've jumped the ports in the fuse panel to send constant power to the pump and injectors, but the problem still exists. All connector plugs to the fuse panel have been cleaned as well. This is work that I have performed. The shop has been performing wiggle tests with the harness but does not seem to located a consistant problem with the harness. I can't help but believe that the problem is somewhere in the harness, but I do not have a copy of any wiring diagrams to perform any electrical tests myself. If the problem is in the harness, I think it may be too tedious of a job for the shop to dedicate to one vehicle,as there are other customers. My father is a master electrician and claims that if we had a full diagram or scematic he could locate the problem. However,this is my first Ferrari and I do not have any type of diagrams. I don't mind doing any work myself, but when respectable mechanics are baffled,I become concerned and slightly frightened. The car is currently back in the shop, but Monday I will request that the plugs and wires are checked fully as well as the wires behind the boots on the crank sensors.Thanks to everyone who posted replies and offered their help, but please keep the ideas coming.I am sure with all the help, a solution is near. Thanks again,

Tim
 
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Discussion Starter · #14 ·
Hey Tim, I'm also a 348 ow

Hey Tim, I'm also a 348 owner who's had some very annoying, perplexing problems. Anyway, I happened across a website of a guy who's an absolute 348 (Spyder) fanatic. The part that might interest you, as it did me, is there are links to websites that you can download the full factory workshop manual for a 348. I downloaded it and just checked to confirm that the section containing electrical schematics seems to be complete. Try the following link

http://webpages.charter.net/aircover/348/1994Ferrari348Spider.html#Manuals

Cheers
Warren.
 
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Discussion Starter · #15 ·
1-Since you know that the rela

1-Since you know that the relays are dropping power,try to pinpoint which wire signal is cutting and make a bypass on this wire.I am sure with your father's help you can do a safe job.
2-Clean all ground points very good
3-Replace battery with a new one(remove the old one)you never can imagine what a battery can do even when it shows good condition.
4-Pull/push and rotate the harness in all directions with engine running and notice changes(do it the hard way,dont be afraid).
Good luck.
Bernard.
 
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Discussion Starter · #16 ·
1-Since you know that the rela

1-Since you know that the relays are dropping power,try to pinpoint which wire signal is cutting and make a bypass on this wire.I am sure with your father's help you can do a safe job.
2-Clean all ground points very good
3-Replace battery with a new one(remove the old one)you never can imagine what a battery can do even when it shows good condition.
4-Pull/push and rotate the harness in all directions with engine running and notice changes(do it the hard way,dont be afraid).
5-If there is a connector between the engine bay and the ECUs section try to clean,(I dont know exactly the configuration of the 348,but this is usually the way i practice in general and it works.
Good luck.
Bernard.
 
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Discussion Starter · #17 ·
Have a look at were the wiring

Have a look at were the wiring loom goes into the engine bay, through the fire wall, behind the seats. There is a rubber gromit that is supposed to be inside the holes. If the gromit is not there the metal from the hole could have cut through the covering of the loom causing a short in the wiring.
 
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