Slowdown, et al.

Do you lose the bank before the SDL comes on? If so, I had a similar problem on my 355 years ago. Bad coil. Intermittent lose of a couple of cylinders, SDL.... Check spark. What codes are you getting, if any.

 

What is code set ..the four digit code ..using the light that flash on dash ...

 

Not necessarily. Bank shutdown due to high temperatures doesn't happen until you get a steady SD light. Different exhaust temperatures result in different indications and effects.

 

Actually, this was my experience. As I said, when it drops a bank (or a couple of cylinder on that bank) check the spark with one of these. Remember, these cars have wasted spark ignition. So if one side of the coil or power module goes bad you lose 2 cylinders. That's enough to cause an SDL and noticeable change in sound and loss of power. If you are losing all 4 on one bank it could also be a problem with the crank sensor fro that bank. But again, first thing to establish is if you are losing ignition. If so, the good news is that coil, power module and crank sensor can all be found pretty cheap. Probably around $100 total for all three.

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You can also try unplugging the Exhaust ECUs (the 6-pin connectors) and see if this solves the problem.

With regard to your question about "What is the ECU doing", if the EGT goes too high (~ 1,700 F (940 C), constant SDL), the Exhaust ECU will switch 12V to the engine ECU's pin 52 which will cause bank shutdown. So, if your problem is perhaps caused by a faulty Exhaust ECU, disconnecting it will mean no +12V can be sent to the engine ECU and there should be no bank shutdown. If you still get a bank shutdown (or partial shutdown), then the problem is something else.

 

4121 is cat temperature too high. 4121 doesn't turn on the CE, just the SDL

4114 is #3 injector. This turns on the CEL.

 

Looking at the 348 2.7 code list, I have:

Driver's side:
4121 Cat temp ECU

Passenger side
4114 TDC control unit recognition. This was discussed recently. May be a Motronic ECU issue
4121 Cat temp ECU

4114 can't be the #3 injector as it was detected on the passenger side... unless it was a RHD car?

 

Yes, but .. see previous post.

Note that there are some variations between the 348 2.7 and 355 2.7 code descriptions. We think the 355 codes may be misprints, but no official confirmation.

 

haha.... So why is bank #1 (the most important bank) on the right hand side?

 

Oops. You are correct 4114 is TDC. Still, no CEL though. Makes sense as I still think this is an ignition problem. But seems odd that he is getting it on both sides.

#3 injector is 1414. (Dyslexia got me again. ) Right side. Passenger's side of LHD.

 

True. Is there anything which would cause problems on both sides? Bad fuel? Timing? Does this car have one cam sensor?

It may depend on the version. On the early cars, the Cat ECUs only control the light and don't send a signal to the Motronic ECU for engine shutdown. Disconnecting some types does generate a fault code, but on some cars at least, no CEL.

 

I was referring to the cat temp codes.

 

4121 does not mean High EGT, it means bad or disconnected Exhaust ECU.

4122 means too High EGT.

4114 may not mean any problem as it may sometimes show when the fault code reading is done with the engine not running. I would leave it for the time being and concentrate on the 4121-s:

Are your Exhaust ECUs disconnected?

 

Many owners (including me) have disconnected the Exhaust ECUs, routinely or otherwise, and have no issues except seeing a "silent" code 4121. "Silent" meaning no CEL, no effect on the engine running and you only see 4121 when reading codes.

The black Vescovini Exhaust ECUs with a 6-pin connector on one side:

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are notorious for failing after rather short time.