My '97 F355 has had just about every thing done to it known to man: 1) Valve guides just done new check valves for injection air 2) QV Manifolds repair 3) Injectors cleaned 4) New Air metering valve 5) Tubi exhaust with 4 different sets of CATs 2 Factory and Two new Hyperflows. 6) New Oxygen sensors and Temp sensors 7) Injection air pump seems to be working normally The persistant problem last 15,000 miles (ever since the car's initial 30K done at 12,000 miles and valve guides done in the last 2000 miles) is that there is an off idle burble in the exhaust when coasting to a stop clutch depressed approx 1500 - 1250 RPM that actually correlates with what feels like an unsteady miss. Once at a stop light, the RPM sags to 1000 after 30 seconds the idle smooths out and only an occaisonal hint of a miss every 30 seconds but otherwise perfectly smooth, A/C on. MY neighbor's '99 F355 with Tubi doesn't exhibit this nor do any of my friends F355s. The problem is most severe if I start the car after it has been driven and shut down for 20 minutes and start it up with the A/C off. It first stumbles at idle. It was so bad, right after the Valve guide job, that so much raw fuel went down the exhaust that my new Hyperflow CATS heated up trying to burn the unburned fuel from these misses. They got hot enough to turn on the "Slow Down" light. I immediately gave it some gas and ran the RPMs up and kept them up and the 'Slow-Down" light went out and hasn't come on since. I have theorized the performance of the New Hyperflows is now degraded enough and my attentiveness to the miss prevents the engine from really stumbling any more so the "Slow down" hasn't come on since. Before, this problem burned up my factory CATS and a new Set of Hyperflows such that excessive heat could not be generated by the CATS but the engine would turn on the "Check Engine" light indicating that the CATS were not working, which they were not because they were burned up by this problem. Currently this is a mystery the local dealer is struggling with but really hasn't been able to put his finger on. Has anybody else had this problem and what was done about it.
Hi Dave, the first thing that comes to mind is cam timing. Do you know if they degreed the cams on final assembly after the guides were done? Other thoughts: Sometimes a lean mixture could also cause the cats to heat up. You could try diconnecting the 02 sensors and run the car for a while to see if they are causing the problem. Your CELs will come on but it won't hurt anything in the short time you do this experiment. Regards, Vern
Both local dealers looked at all the data and concluded it was a cam timing problem before the valve guide job was done. The one dealer that did the work, checked the valve cam timing thinking it was an error on their part at the 30K done at the 12K mile point. Turns out the cam timing was dead on within a few microns. So since the engine was out we did the valve guides. The heads had all new guides replaced and two valves replaced by the local certified Ferrari machine shop all other valves were within spec. Everything in the heads was set to or ground to spec tolerances. The burble in the exhaust existed before the valve guides and after the valve guides. The fuel injectors were found to be bad after the valve guide job (down 15% in flow and with distorted flow) so those were cleaned and brought to new spec. What I'm wondering is whether there is a transient measurement that is going to the fuel control during this coast down to idle that is setting up this miss. When I pull slowly away from a stop without engaging much throttle the RPM sags down to 850 or so but the engine runs perfectly smoothly after sitting at smooth idle. Under any level of power the engine runs perfectly smoothly, its the slack throttle with or without the clutch depressed at speed that causes the burble. Its almost like a DR. Jeckle Mr. Hyde situation at idle with the A/C off. You coast to a stop the engine is burbling when you stop it continues to miss for 20 seconds or so, then its like "OMG", the control says "its missing" and it immediately smooths out and stays that way.
I rememeber hearing something about the secondary injection valve can go bad, the one coming of the headers, and cause idle problems similar to a mis.
I am also interested in the cause of this one. My 97 355 does almost the same thing, but only when warmed up. When started cold, it purrs absolutely smooth and doesn't miss a single beat while warming up. After driving and things are right up to temp, there is a gurgle in the exhaust note, almost like a big american V8 with wild cams installed. THis occurs for a split second every 20-30 seconds while at idle (1000RPM). If I rev up in neutral to 3000-4000RPM and hold steady, the gurgle is still there. Under load, no issue with engine pulling. Notice a "lag" between 2000-3500RPM when accelerating, but attribute that to the lack of torque in this engine at that speed. Cold = smooth Hot = gurgle Is it the electronics doing this, as I know the system goes into a 'closed loop' mode once temps come up. Car is outfitted with Tubi, and hyperflows. Mileage at 7500km's. HELP!?!
GUYS...this looks to be common. I have done much other research as well. My local mechanic says its normal with the Tubi's, but other owners say they don't have this issue. Is there anyone out there that has been through this and has an answer? Beuller.....Beuller...... Thanks guys
I borrowed my car from the dealer who has had it for this problem, for todays club drive. Warm up from cold very smooth no burble. Very distinct difference at warm idle A/C off = rough idle; A/C on = 10 seconds to smooth idle after burbling to a coast down to stop. A/C on warm idle very smooth after 10 seconds @1000 RPM. If I raise the RPM up to 2-3K at a stop light "clutch in" and then let it fall back, A/C "on" warm it burbles all the way back to 1000 RPM, then it is smooth after 10 seconds. If I am coasting clutch in, the windage on the clutch raises the RPM above the 1000 RPM floor and it usually averages 1250 RPM while coasing down to a stop - it burbles at 1250 RPM during the coast down. It almost seems like the Main Engine controller knows when the engine is at min idle and changes the fuel schedule to produce the smooth idle, but once the RPM is above the min idle (1000 RPM) without throttle application it changes to a different fuel schedule. I have a hypothesis that the controller is trying cut the fuel flow to get to min idle so much so that it leans out the engine and causes it to miss, hence the burble. The same may be true with the A/C off. With the A/C "on" it knows it needs more fuel to satisfy min idle of 1000 RPM so it doesn't lean out the engine so much. I'd really like to compare notes with the others with this problem and a good tech who has dealt with this problem and I want to know if there is a solution for all of us.
Dave have you had your air bleed screws checked and the throttle balance checked. There are 8 bleed screws one on each throttle body. Also the balance of the throttle plates themselves need to be balanced like a weber carb setup except you are only adjusting air flow. Also what condition are your 02 sensers in? Regards, Vern
I replaced all O2 sensors and temp sensors with new ones - see list in original post of new stuff. There was no change. Clearly its got to be an air/fuel mix problem for off-idle speeds with no throttle input. I'll definitely suggest this to the service tech.
I have no idea if this is valid for your 355, but I have a similar exhaust burble (but mainly just at idle) and hesitation on acceleration (worse with A/C off than on) in my 348. I haven't isolated the problem yet, but my latest test with a spark indicator tool just showed up 3 wires/plugs/cylinders that were not getting a good spark. It's a $9 spark indicator tool that you can get at NAPA and AutoZone. You just touch it to each spark plug wire on the outside insulation (you never break the insulation or hit bare metal) and it flashes a red LED in synch with the spark firing (if it does fire). I can't help but think that this is going to turn out to be my issue. Maybe it's a quick thing to check for your 355, too. Cheap and quick to do makes it high on my list!
Guys....did the cheap fix....turned off the battery switch yesterday for about 4 hours. Went back out to the garage, turned the switch on and fired up the car. Let it idle (with ALL accessory equipment including climate controls turned OFF) for about 15mins. Let all the temps come up on their own, let the fans kick on and off a few times, then took for a drive. WOW!!! Amazing throttle response at low RPM's...no more hesitation/bog between 2000-3500RPM AND no more gurgle/missfire at idle. I can actually break the back end loose shifting between 2nd and 3rd gear now. The issue was definatly an A/F ratio thing. My exhaust pipes no longer collect a ton of condensation, as they remained completely dry while warming up last night (normally puddles form on the floor of the garage). System has gone WAY more lean, so the acceleration is back baby!! Don't know what would have caused the ECU to go so rich, but it sure was. Maybe my mechanic shut off the battery when doing some work, and didn't use the correct procedure when he fired it up the first time. Who knows....but the issue is solved, and I have way more power now...neck snapping between the gears. Good luck fellas.
I have done this a few times as well with the same positive result, but after a while it goes back to beeing the same again. If you really solved the problem please report back. I just disconnected the battery once again, will try it one more time and hope it will fix it this time. Who knows, it might work ;-)
That sounds totally reasonable. ANY time the battery is disconnected you MUST let the ecu's relearn the warm up process.
I did about 70km's last night. Came home, shut the car off. Let it sit for 30mins., started it back up with no accessories on, let it warm for 5mins, took for another drive....about 15km's and things seem steady and strong. I will report back if the ****te hits the fan again. Don't know if condensation is the result of a rich mixture, but a dry tail pipe is an indication of the correct mixture, in my experience on the track and on the road.
Racer17 - has a simple fix - that should be tried, by everyone that is experiencing this problem. Could you please report back as to how many of you are successful with this approach and how many are still plagued with this problem like I am? I suspect I have tried this over the past two years of my problem (engine was even out of the car for a month- battery off while nose was repainted also another time) with no fix. I will pass this thread on to my tech. One question I have is, if the fix doesn't last, does that mean you need to replace the ECU? If Vern Cornell is right, that it is the idle mixture adjustment, should that be done first, then have the car re-learn its programming. There is also supposed to be a cold boot of the ECU where you not only disconnect its power, but do something else to have it forget everything it learned and start over. Does anybody have any info on this?
Should it make any difference whether you click the battery switch off for 1 minute, 5 minutes, 10 minutes or several hours?
Just a quick update...... Have driven the car now for two days after resetting the ECU's and the car is performing better than ever.....idle is so smooth, both hot and cold, and the throttle response is simply amazing......much faster too, as hte rich mixture was killing the HP output. I love this car!! I have no idea if I shut the battery off for 1min, 5min, 10days if it would have made a difference....maybe someone knows.
This may or may not be a problem on your car, I have noticed that the vacuum line going to the 5/8 banks' fuel pressure regulator is often broken. I look for it every time I do a service and 60-80% of the time it is broken or cracked. I suspect that it gets damaged when the power steering line is separated at the fitting on the firewall. A broken vacuum hose causes a rich mixture on that bank. Its worth a look. But it's hard too see with the motor in the car. E
