348 1 Bank Running Rich, Stalls Occasionally When Hot

MAF, FPR, Cam sensor, fuel pumps, ignitors or coils, lost of possibilities from likely to less likely. I'd try balancing the intakes first, its in the manual, people monkey with those set screws on the TB, set them to the same vacuum both sides.

 

Also if the maf set screw caps are off people monkey with those. That will definitely lean or rich a motor.

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Try turning your air screws out half return and see if that fixes it. If it if it does you have to balance your intakes properly

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All the plugs on the bank "equally" rich?

sjd

 

Bad coolant temp sensor?

 

There is one coolant temp sensor per bank on the 348

 

If one CTS is bad the bank it is connected to may not go into close loop mode and would run rich. I had this happen with my 355 causing it to fail emission due to high HC. No CEL, but checking the codes showed CTS error, 1112.

 

In the engine "V" (left hand side):

Item 43.

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Not sure if the "gasket" (44) is copper washer?

Temperature sensor is item 24 in this diagram (left hand side one):

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Apart from the 2 coolant temperature sensors and the sender for the instrument cluster temperature gauge, I see a temperature "switch" in the 2.5 & 2.7 parts manuals (Item 45).

Anyone know what this does?

 

Bad maf on rich side.

 

Two sensors one for each side same part number the washers or copper. Remove the fuel filter and you can get to them reaching inside. Can't miss them the baby blue.

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Try turning the air screws out on the rich bank throttle body a quarter turn and see if that fixes your stalling. It's a coolant sensor goes bad there is a check engine code for those if I recall correctly.

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There are two of 43. There is only one (each) of the other two types.

 

if you replace it, go to NAPA

Yes, there's a code and the CEL should come on. But in my case there was no CEL on. Just the code stored in the ECU.

 

Keep the temp sensors in mind if it happens again. Mine was an intermittent failure. You can test them by putting them in boiling water and watch as the resistance changes. Should be 1000s of ohm when cold and then drop to a couple hundred when hot. Mine work that way on 2 tests, then on the 3rd test the resistance started to drop as it should but suddenly when to infinite. As it cooled down it went back to normal. If it jumps to infinite the ECU thinks the engine in cold and it goes into open loop mode (rich).

 

#45 "thermometric switch" is a thermo-switch which comes on if engine temp reaches 125C and lights up the high temperature warning light.

Here's the resistance chart of the CTS (Bosch 0 280 130 026):

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