The car in question is a US spec 1985 308 QV. Admittedly I have not driven the car as much as I should in the past year. That being said, the last few times I drove it, it ran fine up until a few days ago. Problem is the only way I can get it to idle is if I adjust the mixture so that it is way rich. Runs ok'ish going down the road, but is definitely not right. I've checked the fuel pressures, which are pretty much the same as the last time I checked them 5 years ago or so. System pressure is 5.4 bar (spec is 4.7 - 5.4) Cold control pressure is between 2.2 and 2.3 bar warm control pressure is 3.9 bar and goes up to 5.4 bar with vacuum applied. Residual pressure holds at 3.2 bar for 20 minutes or more (spec is 2.6 for 20 minutes) The control pressures seem a little high, but are pretty close to what they were when last checked, and the car was running well then. Also, at that time I substituted a new WUR of the same part number (0 438 140 132) and the pressures were virtually identical. I've gone through all the checks as outlined in this thread: http://www.ferrarichat.com/forum/showthread.php?t=257920&highlight=duty+cycle&page=3 and SB 80-29 and it all seems fine (the SB is linked in the above thread). This is where it starts getting interesting, in checking the duty cycle at the frequency valve, with the car running it is about 80%, ok I know it is rich, if I start to lean it out, I can see the duty cycle start to decrease right before it stalls. I've read that with the oxygen sensor disconnected the duty cycle should be somewhere between 50% & 60%, mine goes to about 75%. Further, if I ground the signal lead for the oxygen sensor (engine off), the duty cycle will drop to about 55%. SB 10-13 implies that it should drop to about 20% http://ferrari.cdyn.com/service_bulletins/sb10-13.pdf If I simulate a rich condition the duty cycle will go to about 90% I can tell that the oxygen sensor is working, and it does have some effect on the duty cycle. At times, disconnecting the sensor with the engine running will cause it to stall. I did pull one injector, the spary pattern looks pretty good and it isn't leaking. The injectors in this car were replaced about 10 years and approx. 25,000 miles ago. There are no vacuum leaks that I can find (checked with a smoke machine), so I am at a loss to explain what is going on. Something is making it so lean that I have to artificially make it richer at the adjustment so it will run, but everything 'seems' to be ok, except for the readings at the frequency valve. I'm also confused by the statement in SB 10-13 that states that from MY 1983 the warm up regulator is no longer controlled by manifold vacuum and adjusts for altitude. Both my car (85) and a friends 328 (86) have a hose going from the WUR to the bottom of the throttle housing. I'm also not getting a fast(er) idle when cold, but again I suspect that this is becuase the mixture is way off. The coolant switch in the coolant tank is closed when cold, and open when warm as it should be, and I'm gettting vacuum to the diverter valve for the pulse air system. The oil temp switch is open as it should be, not sure if it is closing as it is not cold enough for it do so. Am I missing something or is my understanding of how the system should work flawed? Any and all suggestions, help, and moral support are welcome Thanks, Jeff
Hi Jeff, 1- The 132 WUR is altitude compensating, so the WSM is incorrect in that respective. 2- On the injectors, 10 years old with 25K miles is a long time on these units. I'd replace them with the new-style Bosch brass ones before going further... 2a-Check/replace the FD return hose, as a restriction here can give you the slightly higher pressures that you're reading. 3-I preseume that your frequency valve is buzzing...If not, this needs to be resolved first 4- Disconnect the O2 sensor and with a 5-gas analyzer, attempt to set the mixture to 1.5% CO and 180 ppm HC, resulting in CO2 being over 13 (pre-cat). If you can obtain these numbers, or get very close, the problem likely lays with your lambda computer. Best, David
David - Thanks for the quick reply, see my comments below. 1- The 132 WUR is altitude compensating, so the WSM is incorrect in that respective. SB 10-13 says that the 132 WUR is altitude compensating, but also implies that it is not controlled by manifold vacuum. I suspect that the SB is wrong in the latter part, as the WUR does in fact have a hose connected to the manifold. 2- On the injectors, 10 years old with 25K miles is a long time on these units. I'd replace them with the new-style Bosch brass ones before going further... These are the newer style brass injectors. Still I agree that CIS injectors are always a problem and it wouldn't hurt to replace them again, but I doubt this is the total cause of this problem. 2a-Check/replace the FD return hose, as a restriction here can give you the slightly higher pressures that you're reading. This makes sense. Which hose is the return hose that you are referring to? 3-I preseume that your frequency valve is buzzing...If not, this needs to be resolved first Yes, it is buzzing away happily. 4- Disconnect the O2 sensor and with a 5-gas analyzer, attempt to set the mixture to 1.5% CO and 180 ppm HC, resulting in CO2 being over 13 (pre-cat). If you can obtain these numbers, or get very close, the problem likely lays with your lambda computer. Unfortunately I do not have ready access to a 5 gas analyzer. A friend has an older two gas that I could use if I have to. But, judging by the way it is running, and how it behaves when I try to lean it out, I doub't I'm anywhere close to these numbers. Thanks, Jeff
Fuel, air, and spark. If your numbers are good on the fuel, maybe you have an air leak between the AFM and the manifold. (Vacuum line to the ignition open?) Does a QV have the throttle position switch? I notice that when the one on my 328 isn't connected, I need to set a very fast idle to keep the car from stalling. That's the down side to CIS: when it finally does go wrong, you have to check absolutely everything, as the whole system is interdependent. But if you're sure it's CIS, you might want to check for the symptoms on a VW board. Veedub delivered more CIS equipped machines in a year than Ferrari did in its history, so the more numerous VW owners will have experienced more CIS failure modes.
If you have a 2-gas analyzer, you should be able to measure the CO and HC levels. Abnormally high HC readings (over 1000 ppm) typically indicate an ignition misfire. Although I'm not suggesting that that may be "the problem", exhaust emissions are a great diagnostic tool. As long as the FV is buzzing, you should be able to get the "numbers" I describe when running open loop. Even though you have the new style injectors, I'd still pop them out (one by one) and inspect the spray patterns. If you have a Bosch "Pop Tester", you could verify the opening pressures and spray patterns. Best, David
