There. I feel better. G.D. car rolled 420+ miles yesterday, and the stupid 1/4 was on for about 300 of them. Cleaned all connections today, reset ECU, let car idle for 15 miles, CEL 1/4 comes back on. Just needed to make sure there weren't old/confuzing codes stored. I'll run diagnosis tomorrow, but I'd bet money it's the f%ing ungrounded O2 sensor on that side. 20 minutes of labor to replace it tomorrow... still, I wanted to buy a new pair of sunglasses instead of a damn O2 sensor.
Daniel, Faster diagnosis= 1) disconnect 1/4 exhaust ecu, rest code, relearn and drive or 2) take airbox off and swap the 02 sensor 1/4 to 5/8 just by a swap of the female connectors left and right. IIRC you can do that without actually swaping the 02 sensors then look for a code to move to 5/8. I forget there are 4 mils. two go to slow down warning mil connected to the exhaust ecu and the other twp mils light goes to 02 sensors and other p-codes for each bank. Make sure you got the right light.
Exhaust ECU's don't exist in my car (shh.... don't tell). Slowdown lamps have been... um.... somewhat extinguished. I am certain it is orange CEL 1/4, as I stared at it for 300 miles yesterday. Engine would occasionally falter at 3k when steady throttle was applied. At full-tilt boogie, no problem. At idle, no problem. FWIW, there are no ground wires on my O2 sensors at all. Toggling the O2 wires is a good idea. The thought crossed my mind today while the airbox was fully off the car, but I got distracted by god-knows-what. Oh yes, a 3-year old.
I cheated with the ground wire. I was not sure if one was really a potential issue but to make sure is just got a 12 10g wire and connected it to the 02 sensor body with a small stainless hose clamp. The I ran the other end into on of the smaller pieces of chassis on a screw. Solved!
Checked code today @ 4121 on bank 1/4, which is odd. Car has NEVER has cat ECU's since my ownership and this is the first time the CEL came on. NO, I'm not seeing the slow down light. Video coming soon...
Maybe I let the smoke out? Tonight, checked everything and the only 1/4 code was again 4121. Went for a very short drive, less than 2 miles, and 4/8 CEL comes on too !! Then, they both go off about 100 yards later. A few hundred yards further, they come back on. Get home, read codes on 1/4 and 4/8. Both banks report 4121, but NOTHING else. Restart car, idle is erratic. dies. Restart again, and holds fire but marginally hunts for idle between 950-1050ish. I'll let it cool down completely then get the O2 sensors out. I **think** the O2 sensors haven't failed by themselves, but they're telling me something very important about the car running (I suppose) too rich. I hate this crap. p.s. One other data point to consider... the last few drives, there is a noticeable burble (deep/throaty) sound on deceleration that I used to have only when the car was fairly cool. Now, it seems to do it when fully warm.
Damn... too late to go back outside. Already have a beer in my hand: http://www.ferrarichat.com/forum/showthread.php?t=197776
^ EDIT. Definitely not TPS pots. Just took them off, smooth as silk. Reinstalled and fired up. Idle was fine for about 2 minutes, then began to hunt again from 750-1100. Near 750 it basically dies, so I shut it down.
Hey Daniel, Could it be a bad Cat choking the engine exhaust? You are pulling 4121 so it is a possibility. The only other thing might be the O2's. My 348 showed similar symptoms after it came out of storage this year. Two new Bosch O2's and the problem stopped. --Mike
Cats are HyperFlow, and have been on the car about 3 years -- through a recent major with no indication of problems. There are no cat ECU's in the car (thermocouple is plugged), so I think the Motornic 4121 is just saying "hey dumbass, where are the cat ECUs?" Could it be a f&*&ed cat? Yes. Even after a long drive this weekend (when the problem first appeared) there was no glowing/red cat, so I don't know if its dislodged or clogged. The fuel smell does seem stronger. When I get the O2 sensors out tomorrow, we'll know more. Tell me what kind of idle you experiences and CEL's.... did the car hunt and die?
I was going to suggest this and but you found my post and beat me to it. The other time I got a check engine light was when I had messed with the MAF settings to try to run leaner since my dyno sheet seemed to imply I was running too rich. I went back to the stock 383ohms and that got rid of it. It did cause some idle problems if I remember. Maybe something else to check?
Hi Daniel, Here is the thread that covered the whole sega: http://www.ferrarichat.com/forum/showthread.php?t=236347 I was throwing the same code (4121) and two more. Three symptoms that are the same as yours are the 1/4 CEL coming on after a two minute warm up, both CEL's coming on together and the erratic idle. After the O2's were changed to Bosch Universals the CEL's went away and the car ran better. Thanks, Mike
Someone much smarter than me has made a private suggestion of why this may occur... Before I post that "idea", can anyone else offer a possible theory? I don't want to contaminate the thought process by offering that first theory. Image Unavailable, Please Login
