360 Cold Misfire Code

I'm slowly getting my new-to-me 03 sorted out and recently completed a major service, including new intake manifold and plenum cover gaskets. Also replaced the RH fuel pump - it was the newer yellow-flange version but I accidentally bumped and broke the outlet port while I was replacing the tank vent valves so I had to swap it out. Sent the injectors out to be be cleaned and flow tested. My only issue is I get multiple cylinder misfire codes soon after startup (like within a minute or two) on cylinders 1,2,3 or 2,3,4 - always the RH bank. I can clear it, and it won't come back until the next cold start, and doesn't happen all the time.
I tried swapping the MAF sensors but no luck. Just to be sure, I bought one new sensor (Magneti Marelli) and installed it in the LH side - still no luck. Swapped both upstream O2 sensors - codes still set. I haven't tried swapping coils yet, but I find it hard to believe the bad coils would all be on the same bank. The coils appear to have been replaced at some point, and the plugs only have a few thousand miles on them. The PO's service paperwork shows that misfires have been noted in the past, but the dealer could never replicate the issue. The intake manifold gaskets had shrunk, but hadn't leaked through yet. Not the most scientific info and maybe it is just me, but it feels like there is more exhaust gas coming out of the RH side for the first minute when the air pump is on. I'm not sure if this is normal, but the exhaust does smell rich when you first start it. Never any white smoke to indicate any deeper engine issues. I'm running out of ideas?

 

It seems to idle smoothly when cold, but it certainly sounds rougher/louder when the air pump is on. I've wanted a smoke tester for a while - sounds like I have a good excuse now. Thanks - will give that a try.

 

Great suggestion - I'll give that a try. It is considerably louder for the first minute when the air injection is on - is that normal? My first Ferrari so I'm not sure. I double checked my intake manifold nuts and they were all tight, and I even tried a cold start with the vacuum brake booster line pinched off with no improvement. If I rev the engine slightly I can get a pending code (flashing MIL) to shut off before it sets a permanent code. I do notice it hesitates when cold if you blip the throttle - again not sure if this is normal?

 

When I say I blip the throttle, the rpms hardly rise but rather it leans out and bogs. I also did swap the two upstream O2 sensors already.

Thinking about this more, I'm thinking if the air injection rate was too high it would appear to be running lean, so it would fuel it more. Not enough air and it would look rich to the )2 sensor, so less fuel and leading to a misfire? I assume I have a lean misfire and not a rich, based on never seeing any smoke (just the smell, but again I'm not sure if this is normal).

This has got to be a simple problem - I hope. Thanks again.

 

Thanks everyone - you've given me some new things to think about.

I haven't checked the fuel pressure, but since the RH fuel module is new I'm assuming for now it's ok. It runs fine otherwise too.

I know it had misfire codes for the PO before I worked on it, but it has gotten worse since I did my work on it. I did the intake and plenum gaskets, and spent a lot of time making sure everything was perfectly clean so I'm very confident everything is correct. I'm wondering now about the solenoid valves for the intake equalization and switchover butterflies, since I did move those around to more easily install the RH fuel module and the new tank vent valves.

If a purge valve was stuck open it wouldn't pass its EVAP leak test. Since I never get that code, I don't think that is an issue.

I'll go over everything again, and if I don't find another I'll try a smoke test. I suppose I could always disconnect the two vacuum lines to the vacuum canister too and isolate that circuit from the engine entirely.

I'll post what I find out.

 

I've been fighting with this issue now all summer, to no avail - I still get misfire codes on cold starts on three out of four cylinders on the RH bank right after it goes off its cold start cycle. As soon as it smooths out after going off cold start, the MIL comes on. I've gone as many as seven cold starts with no MIL, but it usually happens every cold start. Once I also had a misfire code for the LH bank, but only once. To recap, as part of my major service I replaced the intake manifold gaskets. I've also purchased a new MAF and tried that in both banks, swapped upstream O2 sensors, finally just bought new O2 sensors, individually blocked off the vacuum lines to the brake booster, the canister purge, and the rear vacuum lines to the air injection, plenum, & exhaust cutout valves. Measured fuel pressure on each bank, and RH bank has a new fuel pump anyway. Running lean doesn't seem to be an option. Thinking I maybe had one cylinder running rich making the others be leaned out, I swapped the coil packs between banks, and also swapped the injectors (that had been cleaned and checked by RC) between banks with no improvement. Also swapped a couple spark plugs around. Checked the air injection solenoid valves to make sure they weren't stuck open. Finally added ground wires between the ECU's and the fuel rails. It certainly doesn't sound like it is misfiring, and runs great other than the MIL.

After doing some more reading, I see that 360's (even later ones like my 03) can suffer from "phantom misfires", and that sounds like my issue for sure. Is a 360trev tune in order, as I'm out of other ideas?

 

I haven't tried a smoke test, but I have sprayed starting fluid around the intake runner area immediately after a cold start with no rpm change.

I'm not sure how common the misfire codes are, but I've read about them in several threads. 360trev also has a Powerpoint on the web where he talks about how his tune can eliminate the "phantom" cold-start random multiple misfires. I read in another thread where they might have been a factory calibration fix, but I'm not sure if I have it.

 

I usually don't touch the gas pedal when starting. However, it seems at times I've had better luck at keeping the MIL off by bumping the rpm up a couple hundred.

When I try to increase the rpm while it is still in cold start mode, it is difficult to hold a constant speed and it does run a little rough, in my opinion. Is this normal? As I've mentioned before, I also have to very gently depress the accelerator or it will die out. As soon as it goes off cold start after a minute or so, it runs great. The failure to accelerate would point to it running lean, but it sounds and smells like it is rich.

I usually just erase the multiple misfire codes, but I have also done a reset by shutting off the battery switch. Right after doing that was the time I was able to go seven cold starts without a code. I've done that a couple times since, and it didn't seem to help so I'm not sure if that provides any clues?

I believe the PO had an ECU replaced by the dealer with a used one a couple years ago. based on other work I've seen what they've done to this car, I'm not 100% convinced they actually know what they are doing. Is it possible they didn't flash the :"new" ECU correctly? Just grasping at straws here.....

I've checked for exhaust leaks and I don't hear any odd ticking, but I'll check again.

Is there anything I can learn from the fuel trims? I have both the Autel AP200 and Thinkdiag scanners. I can now consistently connect to the TCU with the Thinkdiag (thanks to flash32's advice) , and usually just one of the engine ECUs. As soon as I try to switch to the other ECU, the live data starts to not make sense for either ECU. I'm using an iPhone, so maybe that is part of the problem? I haven't tried the Autel as much yet.

 

Problem solved! Thinking I had the phantom misfire issue, I messaged Sammyf about my trials. He contacted me back right away, and he stated they see the phantom misfire issue primarily on EU spec cars. He was intrigued though by the LH ECU replacement that the PO had the dealer perform back in 2022. He had a tablet and cabling sent to me to scan my two ECUs , and sure enough the LH ECU (from a MY2000) had never been reflashed to my MY2003. He was able to remotely copy from my original RH ECU and flash it onto the LH ECU. After reinstalling the ECUs and a quick throttle relearn, I am happy to say no more codes! It runs noticeably smoother and quieter.

At this point, since I already had their tablet, it made sense to get my own 360trev tune. A couple days later we flashed the new tune to the ECUs, and I can vouch for everyone else's comments that have been made over the years that the difference is incredible! It is especially noticeable that it pulls so much harder in third and fourth now.

I can't thank Sammyf enough for his help, as I was running out ideas and felt guilty I couldn't find the problem after months of trying. I learned so much from him regarding how ECUs can be swapped, and that there was likely nothing the dealer themselves could have done to update the used ECU. Of course, thanks to 360trev too for all his work in developing these tools - it saved my car (and my sanity!).