I would appreciate any comments regarding the following situation with the air pump during cold starts. After changing the spark plugs (NGK 8A) and installing recall kit no. 48 (fuel block) , I'm having a problem when cold starting my 1998 355. Although the car starts on the first try, it stumbled and hesitates for about one or two minute before idling steadily at about 1,200 rpm. After a few minutes idling at 1,200, it reduces the idling rpm's to the normal 1,000 rpm. The air pump was not working (blown fuse). I replaced the fuse with a 15A. No change. After several cold starts, the car began starting perfectly (begins idling at 1,200 rpm almost immediately and, after a few minutes, it comes down to 1,000 rpm). Nevertheless, I noticed the air pump whine was absent (blown fuse again). It starts better without the air pump! I'm afraid this is not right. What should I look for? Any suggestions? Apart from the situation described, the car is working perfectly.
After changing the plugs and the fuel block the car should have gone through a relearn of the idle parameters (10 minutes of idle with A/C and heater off no throttle application). ECUs today constantly seek to relearn the engien's current state of tune and asjust it back to nominal. When you change something (like the plugs) the current state of tune is enough different the ECU has to relearn where it is. The air pump is a random side effect (in my opinion). But still blowing fuses is not "normal".
You might also want to replace the Bosch relay for your air pump. The location of the Relay is in your owners manuel so you can get the part number. My car runs horrible when the air pump is not working. I have replaced mine twice. It is easy to replace. Good luck!
I assume you mean your car runs horrible for a short period of time, correct? The air pump only runs for a few minutes to help get the cats. up to proper temperature. Even so, it should not have any major effect, I would think. You're only pumping extra air into the exhaust system and the engine ECU should not be "listening" to the o2 sensors anyway until the air pump stops (otherwise they would report a very lean condition with all that extra air).
I would pull the air pump out and then connect it to a car battery via the correct size fuse. If it blows the fuse you probably need a new air pump. It would probably have shorted windings in the motor or something inside is causing a lot of drag (bad bearings etc.) which increases the current draw beyond normal and beyond the fuse capacity.
The common fix for blown fuses on the air pump is to replace with a fuse 5amps higher. I believe this is an FNA approved fix, as my car had this done at the dealer, and seen it on a few other 355's as well. So if stock is 15, try a 20, but I would not recommend going higher. If it still blows, then you will need to replace it. Apparently Ferrari did not get the fuse rating correct the first go around. Not sure why it would run worse with the air pump...bad check valve?
Yes, at startup is what I was referring to. I have a 1995 355 2.7 motronic and without the air pump working, my car would idle very low at startup and take a very long time to get to temperature. I replaced the fuse with a 20 amp, replaced the Relay, and the Air pump. Car was perfect after that.
It sounds like you had some other contributing problem(s) then.... vacuum leak or something like that which happened to get rectified when you replaced the parts. The air pump should have no effect on the idle speed and certainly not on how quickly or slowly the engine reaches normal temperature.
