Car is running VERY rich all of a sudden
I posted this over in the Gen III forum but haven't received any responses so I'm trying here...
Had my 01 procharged Z06 on the rollers a little while ago just for kicks before I started hitting the road courses again this year. this is the same dyno I always use and my results have been a pretty consistant 730whp SAE all the time regardless of the time of year.
the car is running an EFILive custom OS (its an 03 OS) with an SD tune that Cartek did a couple years ago. For hardware I'm running 96# injectors, an injector driver box, two fuel pumps (the second activated by a hobbs switch) and a boost-a-pump. Previously my A/F has been mid-low 11's on this dyno.
For some reason this time my A/F was a super rich 10:1 all the way from when I went WOT until I lifted @ 6.5k RPM. It might have been richer then that but the WB sensor on the dyno only goes to 10:1 as the richest. As a result power was down about 40-50whp and about the same decrease for TQ depending on the pull. On the street I can't notice the power difference at all but my fuel economy has always sucked and my car is DUMPING black smoke out the exhaust when I step on it.
Any idea what would cause this sudden rich condition? I'm thinking it might be a stuck injector or maybe my injector driver box is messed up or something, but I'm thinking its a mechanical problem and not something with the tune because aside from swapping in new head gaskets recently nothing has changed on the car.
I recently installed an innovative LC1 wideband and purchased EFILive V2 flash/scan so I can start to log/tune. I'm not new to tuning an engine but the EFILive software takes a little getting used to. The wideband is all over the place most of the time. even at idle it will swing from super rich to 18:1. I can get the A/F to read about 14.7ish when crusing if I'm VERY light with the throttle, but any real movement of the go pedel and the WB shows a rich condition.
Here is the part that is really weird and makes me thinks its an injector or driver box issue. When in decel above 2k RPM the injectors should be shutoff and the engine is basically just pumping air, so the WB should read 20.9% oxygen, which is the amount of o2 in the atmosphere. when I left off and coast down however its showing as rich as 8:1 A/F, which is a low as I have the gauge set. Sometimes if I coast down from like 4k or above it will show 20.9% o2 for a could seconds but it will always go to 8:1 after a very short period.
some other things I suspect "might" be a problem but don't know enough about how the EFILive SD tune calcs things are:
shot front o2's - i haven't looked at my fuel trims yet, still trying to get the logging program bugs worked out. Plus I don't know if the SD tune uses the front o2s for anything but it is possible they are shot from the few times I put leaded gas in the car.
boost leak - again, not sure how the SD tune operates but it should be reading the pressure in the manifold and adding fuel accordingly. if there was a leak it should effect the fueling, correct?
Faulty WB sensor - I'm just grabbing straws here. I doubt the dyno's WB and my LC1 are off. plus the car is DUMPING black smoke out the exhaust when I step on it which is a clear indicator of a rich condition.
Faulty Coolant temp sensor - ???
Bad 03 OS - I read about a bug in the 03 COS that does something with the coolant temp sensor. Could the situation I'm seeing be a result of that bug?
sorry for the long post but I wanted to put as much info out there as I could so people can get a clear picture of the situation.
what do the experts think?
