348 after engine out issue

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Is there any adjustment for the TPS on the 348? On my F355 the screw slots/holes in the TPS base allow for slight movement to get the TPS resistance values back into the required range.
Do you have the resistance range for the 348 2.7 TPS?

Note that an improperly adjusted throttle cable may not allow the throttle quadrant to go to its proper idle endstop.

 

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2-3 is the important one at idle. i.e. no more than 850 ohms +/- 153 ohms

 

According to the 348 WSM, the TPS balancing is done by the voltage measured between ECU pins 53 and 19 (ground). As this is not easy, I measured the voltages on the TPSs as follows:

Left TPS - between Pins 1 (ground) and 3
Right TPS - between Pins 2 (ground) and 3

Instead of tapping into pins 1 and 2, it should be ok to simply measure the voltages on the TPS Pins 3 and a good ground point. The mounting holes on the TPSs are not slotted but they allow small adjustment. If the difference between the left and right readings cannot be brought to within 80 mV, the reason could be too much difference between the gaps of throttle bodies butterflies or because the butterflies are not fully returning to their stops when in idle position. Extract from the 348 WSM:

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Is the old one any better?

Is there anything impeding the return of the accelerator pedal?

You may need specialist help. Adjusting the mechanical linkages may allow a lower voltage setting on both sides, but you may upset the airflow balance between the banks.

 

It is not adjustment of the linkage but adjustment of the butterfly stop that will change the position of the TPS at idle and, consequently, change the voltage reading on the TPS Pin 3.

As stated in the above extract from the WSM (see the first para), the correct adjustment of the butterfly stop is when the gap between the butterfly and the housing bore is 0.02 to 0.05 mm.

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Here is the link to how I adjusted the TPS on my former 348.

https://www.ferrarichat.com/forum/threads/348-throttle-position-sensor-adjustment.453969/

 

Does this adjustment affect just one bank or both?
At what point do you have to start playing around with vacuum gauges and such? Is this only for balancing individual throttle bodies, not banks? I couldn’t find a procedure for the 2.7 (348).

 

Setting the butterfly gaps (openings) at 0.02 - 0.05 mm via their stops does not balance the banks and does not set the idle speed. The mentioned gap means almost fully closed butterflies and the gap is there to prevent their binding in the bore. It also sets the TPS at 400 - 600 mV at idle position (this is what I observed on my 348). The gaps are set at the factory and should not be altered but, sometimes, they are unnecessarily changed to larger butterfly openings resulting in too high baseline voltage readings at the TPSs which may "confuse" the ECUs.

Adjustment of the linkage is only for the purpose of getting both, left and right, butterflies to start moving off, and return to, their stops at the same time. As it is not very easy to observe the starts of movement of the butterflies from the idle position, I adjusted my linkage by listening to the "clicks" as the butterflies hit their stops when I quickly release them to idle position.

After the above "geometrical" adjustments, comes the setting of the air bypass valves on the throttle bodies. On my 348, I found that 1 to 2 turns of the adjuster screws out from fully closed works fine. Positions of these screws set the baseline for the Idle Control Valves (ICV) from where the valves control the idle speed. I did not notice any difference between having the bypass screws at 1 or at 2 turns out. This is because the ICV ultimately sets the idle speed - with smaller opening of the bypass, the ICV will open more at idle, and open less if the bypass opening is bigger. This is why the idle speed cannot be changed by changing (within the reasonable range) the openings of the bypass screws, unless you open them so much that the ICV is no longer able to control the idle speed. In such a case, the ICV may fully close but the large amount of air flowing through the wide open bypass may still keep the idle speed to high.

So, for the "joshtownsend's" adjustments, I would recommend the following procedure (In the absence of the Ferrari special tool):

1. Disconnect the battery, remove the throttle bodies, check the butterfly gaps and adjust to 0.02 - 0.05 mm if required. Verify that the butterflies hit their stops when in closed position and that they don't bind. Take this opportunity to remove and clean the bypass screws and their orifices.

2. With the linkage disconnected from the throttle bodies (or making sure that the linkage is not preventing the butterflies from hitting their stops), check the voltages on the Pin 3 of the TPSs. If they are out of the 400-600 mV range, small alterations can be made by twisting the TPS (as allowed by the holes) before tightening the screws. If a bit more rotation of the TPS is required, I would file the holes as needed. At the same time, ensure that the voltage difference left to right is no more than 80 mV. On my 348, I managed to set both TPSs at 480 mV, i.e. zero difference left to right, but this is not necessary.

3. Connect the linkage and adjust it so that the butterflies start opening (or close) simultaneously.

4. Set the bypass screws at, say, 1.5 turns out. Connect the battery and perform the "re-learning" procedure: with everything "off" start and run the engine, at idle only, for about 15 minutes. During this period, you will notice idle speed fluctuations as the two ECUs are synchronising the idle speeds of the banks.

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I'm still not too sure of the geometry of the system on the 348. The parts manual doesn't really show you what's happening. Will or won't the TPS's go to 400~600 mV if, say, the throttle cable is too short or something above the accelerator pedal is stopping the pedal returning to idle? When I replace a frayed cable on my 355, I wasn't sure of the procedure, so I simply made sure that the quadrant went through full travel (and hit its endstop). The TPS value was still too high. The ECU seems happy, so I am happy

I wish this subject had come up earlier. I would have asked my tech to fix it up for me. I don't want to do any filing of holes until I know my butterfly gaps are ok. The idle rpms are ok, so the IAC/ICV is doing its job.

It was noted on the 550 forum that incorrect cable adjustment was leading to power loss. Power was restored by adjusting the cables.

 

These would be abnormal conditions and would need to be fixed. As mentioned in the first paragraph of the extract from the WSM I attached earlier, the voltage reading of 400-600 mV assumes that nothing is preventing the butterfly from sitting on its stop at idle position. Of course, if the butterflies are prevented from returning to their stops by tight (no slack) cable, or sticking pedal etc., the voltage reading will be affected. Trying to adjust the TPSs in such a situation would be pointless.

 

As you are backprobing the connectors on the car side, I suppose a high resistance at the connector pins/socket could cause a higher voltage reading. The higher the resistance, the more the voltage drop (assuming the internal resistance of the ECU remains the same). I can't remember if you tried cleaning the pins/sockets.

The ECU on the faulty side could be putting out the wrong voltage leading to a higher mV reading. What happens when you swap ECUs?

 

I say this with reluctance because I know it will = a lot of tedious work.

But here it goes anyway………

1) New EPROMs
https://www.ferrarichat.com/forum/threads/348-ecu-removal-chip-removal.351819/

2) Re-pin of the T55 connectors
https://www.ferrarichat.com/forum/threads/348-motronic-2-7-connector-harness-repin.444155/

 

The left and right TPSs rotate in opposite directions, one turns clockwise and the other anticlockwise. This is why at WOT, if connecting your voltmeter to the same pins left and right, you get 4.41 V on one and 0.144 on the other. To compare the left and right readings correctly, measure the voltages as I informed in post #31 and you should get low voltage at idle and high voltage at WOT on both sides.

However, you do not need to bother with the voltages at WOT just take the readings at the idle position. If you took the idle readings of 0.642 left and 0.952 right on the pins as I mentioned in the post#31, then, obviously, they are still both outside the specified range, the right one very much so. it should not be difficult to bring the left reading to below 600 mV by some filing of the TPS mounting holes but the right one needs further investigation:

First, make sure the grounding points on your cylinder heads (2 at each timing cover) are clean (not tightened over paint) and not loose. See the picture below.

On both TPSs, check the voltages between ground and Pin 2. The readings should show 5.0 V on both sides. These voltages are supplied by the ECUs.

Also, in order to double check your measured 0.642 and 0.952 volts, repeat the readings by connecting your multimeter between a good ground point and Pin 3 of each TPS.

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CORRECTION: Check the voltages ground to Pin 2 of left TPS and ground to Pin 1 of right TPS. The readings should show 5.0 V on each TPS.

 

I went through all that as well, remember your throttle linkage affects it if it has been messed with by others prior. It may gap perfect with geometric method but be off with throttle linkage attached. Disconnect that sides throttle linkage then check it.