95 keeps fouling plugs, thoughts?

Leaking injector?

 

That happens on occasion with other cars so it'd be my first thought in this case since I believe you have two fuel pressure regulators, which pretty much eliminates them from the list of candidates. Wouldn't be a bad idea to replace the CTS (coolant temp sensor) for good measure, but even if you don't I'd suggest treating the connector pins with DeOxit D100 for a while, then cleaning them with spray cleaner and following up with DeOxit Gold a couple of weeks later. Any resistance in the wiring between the CTS and the ECUs changes the temperature that the ECUs see.

Disclaimer: I'm not a 355 owner, but I've chased these issues on other Motronics cars and those procedures have worked well.

 

Time for an Italian tune-up

 

MAF

 

What plug are you using? 95's take a different plug than other years because they are known to foul if you just start and shut off. They run richer than other years. I have piggy back computers to change fuel and timing and the tuner took out a lot of fuel on the low end. Don' t turn off until you are off the enrichment cycle and make sure you are using the correct plug.
Spark is weak on these cars.

 

Driving a 355 in the 20s is not a 'no no'. I've driven mine here in NJ at that temp as long as there's no snow/salt on the roads. There should be no problem with cold weather driving at all.

 

Except lighting up the tires!!

 

Check plug heat range. 95 run a hotter plug than other years to prevent fouling.Avoid running a few minutes and shutting off. Should run until fans come on so you are in the 190 degree water temp and off enrichment. 95's run rich.If still running rough on occasion and plugs are good, check thermocouple ECU. For a few years my car would suddenly feel like running on 4 cylinders. It would happen randomly. Turned out bad thermocouple ECU that would shut down a bank so I was running on 4 cylinders When you ran to store and shut it off, what was your water temp reading? If low, like 100 degrees you were still in enrichment cycle which is really rich on the 2.7 cars. I went through all these problems with my 95 in the 17 years of owning one. They are different than the other years.

 

Yeah you better have winter tires below 45 degrees.

Tires are the most ignored safety feature on cars.

Might as well be driving on ice.

 

As others have said I would try both the intake and exhaust related sensors. MAF: clean it. Would a bad O2 or thermocouple not give an error code? I don't get why he would say they're both bad, I mean the chances of both being bad, especially the thermocouple are pretty slim from what I know.

More likely the ECUs are bad if anything.

Also, if one injector was bad I don't think all your plugs would be fouled but it doesn't hurt to have them all cleaned. I cleaned mine and the car runs a bit smoother.

 

Bad TC or TC ECU would generally not result in fouled plugs. Worst case is that it would cut off fuel to a bank which would not fouled plugs. Bad O2 sensor would throw a code. So would a bad MAF. You might consider checking spark when the engine runs rough. Could be an intermittent ignition problem. Been there. Start and drive one day, perfect. Next day, start and it not hitting on all eight. A day later, fine again. Can be a ***** to diagnose but fortunately coil, ignition module and crank sensor are cheap if you know where to get them. Just search on the Bosch part number.

 

Not necessarily, depending on how bad it is. If the coolant temp. sensor is just out of calibration, it may be signalling that the engine is still cold causing the ECU to provide enriched mixture.

 

I had a problem with two plugs fowling and it turned out to be the wires.