For the past 3 months I´ve been working in getting my 355 to not just look great, but run great and sound awsome. New things: Front paint, mats restored, tires, timing belts, bypass valve checked out, air valves checked out, new bypass hose, alternator restored, new clutch, injectors cleaned up, new alternator band, new gas filter, power modules cleaned up, new cats (Hyperflow), new exhasut (X-OST), new temp sensors, new oxigen sensors, new spark plug wires (Kingborne - spark plugs inspected and looked fine), cillinder pressure ok. No check engine light nor slow down coming up. However, the car doesn´t sound smooth when iddle and we are clueless about what might be the problem. I have shut down main switch to let ECU restart but no change. The car has kinda an interrupted sound, like one of the banks shakes a little bit more and a br, br, br, sound come and goes avery 10 seconds or so. It is not a taping noise, is more like an inconsistancy (puffy kind of sound). Some say that if the check engine doesn´t light up it wont tell the type of failure. Any one´s input is appreciated.
Could be a lot of things. You've got 8 throttle bodies on a 355 that must be synchronized in order to have smooth power, for instance. That won't always set off a trouble code, either. I'd want to find out my fuel air mixture ratio and exhaust pollution components on each bank (e.g. with an exhaust sniffer), and I'd want to measure the temperature of the cats, for starters. I'd want to check my voltage (an initial test of just plugging a DMM into your cigarette lighter) for another thing. What's my voltage when the engine is off, when engine is on at idle, and when engine is at high rpms? With the above information I might be able to narrow down my problem area.
Might also clean the connectors and treat them with Stabilant 22, that go to the idle control valves and Mass Air Flow Sensors. But it sure sounds more ignition related....
That is *so* true, Dave. I had my idle racing up and down yesterday. Popped my hatch and sprayed marine Corrosion Block on both ends of the ground strap from tranny to frame on my 348, and within a minute or so the idle was back to normal. Didn't even turn a wrench.
Yup, my 355 had the idle going up and down (not rough) and cleaning/treating the MAF connection fixed it.
First of all thanks everyone for helping. The mechanics at Weber automundo (in Monterrey Mex) decided to check connector by connector and wire by wire and finally found out there was a crack in one of the power modules (were the spark plug cables connect). This causes the spark to jump out of place and the car does not run smooth. After checking both pieces, I decided to replace both with new ones. Got them at Ricambi in no time and Car is running as new!!! Hope this is of help.
