348 Hot Start Issue: I Have Tried Everything!

I used to have issues on one of my cars (not Ferrari) with old vacuum hoses in the engine V getting soft when the engine was hot. They collapsed. How close are 348 fuel regulator vacuum hoses to heat sources?

 

After switch off, the fuel pressure is held by the pump check valve at one end and by the FPR at the other so fault in any of the two can cause rapid fuel pressure drop. I remember you earlier mentioned that one of your new (PR298) FPRs was leaking fuel into the vacuum line. You did not comment further but I believe you replaced it with a good one. This issue, coming with a new FPR, suggests that the Standard FPRs are not really great quality.

 

I got a 94 spider , with hot start problem. I got fuel pressure regulators coming Tuesday.

 

Further to my post # 26 - FWIW ?
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From an earlier post -
“bought an infrared gun and my driver side cat flange is running around 270 deg and the passenger side cats are only 170 deg! I believe this is evidence that there is an ignition problem on the passenger side”


From post #57 above
“If I unplug the passenger side crankshaft position sensor while running there's just the car continues running as before but if I unplug the driver side crankshaft position sensor the car immediately dies.”


Me - these contradict , but happy to stand corrected . ???
Cooler should be the faulty side ?

 

Did you try swapping the ignition coils left-right?

 

I believe you mean "camshaft position sensor" here.

It doesn't really seem that you have any issue with ignition timing. The ignition timing is controlled by the: 1. Engine ECUs (no problem there, you swapped them); 2. Crankshaft Sensors (no problem there, you swapped/renewed them); 3. Camshaft Sensor (would cause problem on both banks, not only one); 4. TPS (did you try swapping them?).

Timing belt skipping is theoretically a possibility but it would affect both, cold and hot starting. And to affect the combustion so much it would have to be a skip of a few teeth which would cause bent valves before the kind of misfire you are having.

You mentioned that you have a solid spark on all four cylinders (of the offending side, I presume). When an ignition coil is on the way out, it will usually still produce a visible spark but you may not be able to tell how strong that spark is. Partially faulty ignition coil will produce sparks of reduced intensity which may not be able to ignite the mixture efficiently so there will be many "misses". And it usually gets worse as the coil heats up. The problem diagnosing this is because it is difficult to distinguish between bad fuelling and bad (poor) spark.

I once spent months chasing a reason for engine misfiring and dying when it heats up (after a few kilometres of driving) and be impossible to re-start until it cooled down. All the time, I was blaming the carburettor, cleaning and readjusting it many times, to finally find out it was the ignition coil.

 

The fact that the situation is slowly getting worse, is indicating a problem that is intensifying. As you replaced a lot of sensors already, with no effect, would indicate that the main problem is not in sensors or coils. It most likely is in a part/situation that is deteriorating. Hopefuly increasing resistance in a wire or connection. Unfortunately, if it is in the timing belt, it would mean that from 1 tooth it now has skipped another one. If that is the case, chances are that with the violent backfires it can skip another one , and then you are in the danger zone. 3 strikes/teeth and you're out...
I would not try to start it again, but do a new compression test first. All plugs out , should be less stress on the engine turning.
if there is a noticable difference in the pressure on both sides (or compared with earlier tests), you have an indication. Do not use 10 rounds or so, but just 4 and see if there is a difference.
As with 10 rounds of starting, the pressure gauge will in the end show a rather normal pressure even with 2 teeth skipped. What indicates is the speed in which it gets to a max pressure. With 4 a normal timed engine should already be near max.
That said, I am also just an amateur, if professionals see this differently, please react.
Other indication is the voltage of the O2 sensors (or short term fuel trims), but for that the engine needs to be running, which I would not dare anymore at this point.

 

Just one tooth out can show significant difference between the banks. My engine was running well and had quite smooth idle but, when I decided to just check the compression, I was surprised to get the following readings (13,000 miles engine at the time, I did about 10 rounds on each cylinder or until the gauge needle stopped jumping any further):

Left bank: .......200 psi (all cylinders exactly the same)
Right Bank:.....240 psi (just one cylinder read 239 psi)

I then checked the cam timing and found out that the left intake cam was 1 tooth out (late). The belt was still in excellent condition and tension so I concluded that the left intake cam sprocket was, most likely, engaged incorrectly during the previous belt service. Anyhow, after I timed everything correctly with a new belt, I had the compression readings 240 psi (+/- 1 psi) on all cylinders.

Perhaps I had such a significant compression difference for just 1 tooth out because it was on the intake cam. In the case of one exhaust cam being out by 1 tooth, perhaps the compression difference would not be so grate.

In any case, doing a compression test is a good (and quick) method to check for any compression difference left to right which would point out to incorrect cam timing but only if the readings show similar values across the 4 cylinders of each bank but a consistent difference left to right.

 

Really sounds like a bad wire somewhere that's getting worse as things get plugged in/unplugged.

 

Have you already ruled-out or disconnected the Cat-ECUs ?

 

Do you have two cam sensors or one?

 

If it were to only affect one bank, the pink wire pigtails on the car side of the connector would have to be faulty.

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I think this is normal because the Cam Sensor signal goes to both engine ECUs and they probably talk: "I displayed 4112 last time, now is your turn". If, however, the code was consistently displayed by only one ECU, that would point to a possibility of a wiring fault as mentioned by Ian above.

In any case, it is a good idea to have a good look at the loom side of the Cam Sensor connector, especially the crimping of the pink wires to their pin and the condition of the pin itself. Here's what this connector looked like on my 348 when I bought it:

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Good to hear the timing is still ok! No direct risk in harming the engine by testing it further I think.
If you have some spare time, a compression test is still a good idea to see if there is a problem with the valves.
Possible overheating of the combustion chambers could have affected the valves. Very, very small chance, but with all things done so far, it must be something that is considered a small chance. Even though I hope it is that cam sensor plug. (tried wiggling it with the engine running/starting?)

 

I presume that there was no such rubbing on the original Cam Sensor but, if there was, maybe you should check whether you have both locating dowels for the sensor housing. The picture below shows the locations of these dowels on the cylinder head (the pic below shows only one but there should be two where the red lines are pointing). Note: If you decide to remove the sensor housing for inspection (if you see rubbing marks on the original sensor), be very careful when re-attaching it in order not to fold back the seal lip (second pic).

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