360 Replacing the relays inside the immobilizer to fix cold-start stumbles; any advice?

I’ve been discussing remedies for intermittent cold start stumbles with several parties over the last year or so. It’s inconsistent and doesn’t leave codes behind. It’s only the first start of the day. Every subsequent start is flawless. And it only seems to be in colder weather. From roughly October to May it was perfect. I live in New England and I drive the car year-round. After checking myriad items (alarm siren, main battery, ground points) I’m left with the suggestion of old sticky mechanical relays inside the immobilizer not allowing both banks to start in unison consistently. I bought all 4 of the mechanical relays that are soldered to the board inside the immobilizer. My plan is to cut main power, remove immobilizer, have the relays all de-soldered and replaced, reinstall and relearn.

My brother in law has a car audio business and is very experienced with electronics, motherboards, etc. I had a previous issue with the KESSY (aka immobilizer) unit in a Cayenne Turbo, which would brick the car in a no-start state. It was and is a common issue in those cars. I had to keep my laptop and Durametric cable in the car with me at all times so I could clear the fault and start the car simultaneously for every start cycle or it would leave me stranded. Desoldering and replacing that relay fixed the issue once and for all.

Mortal of that story is that I’m comfortable with the ability of my BIL to remove and replace those relays. My only question/concern is if R&R’ing the relays will disrupt anything else in the system in the process. I just don’t want to brick the car in an effort to pursue nice, smooth cold starts.
Obviously I’m hoping for a fix to this issue, but at the very least, I don’t want to create a bigger problem.

Expert thoughts and advice?

 

I can't see how it's an immobiliser issue, Jeremy. The Immobiliser ECU only talks directly to the RH ECU. If the RH ECU doesn't unlock, I assume the LH ECU won't unlock (the RH ECU sends the unlock signal to the LH ECU).

If you use that technique I explained to you in PM, you can see if the immo is causing the issue.

i.e. When the car is cold, put a 12 volt, 50mA wheatgrain lamp across the fuel pump relay solenoid pins and try to start the car.


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If the lamp illuminates, the immo is ok. The pump won't be commanded on if the immo is bad.

But try it on the other bank as a comparison. The pumps won't be commanded on if other things aren't working, too (crank sensor and possibly the cam sensor). But if the light IS illuminating and the other things are ok, it's not the immobiliser.

 

Ian, to be honest, I don’t know a single thing about what I’m talking about. I’m just regurgitating information that’s been offered to me throughout the process.
I know @360trev offers an immobilizer delete as a feature on his tunes, mentioning that it may eliminate cold-start idle issues. He mentions that the mechanical relays inside the immobilizer get old and sticky and can start to fail and cause these issues. Hence my inclination to swap the relays out and see what happens. If nothing else, and it doesn’t fix it, at least it’s eliminated. I know IMMO relays have been proven to leave Cayennes like mine for dead, so it stands to reason that it may be true for our cars as well. Perhaps since there are 4 relays total in the IMMO, maybe it would only take one of them to get sticky to allow one bank to start while experiencing a delay on the other one? Again, I’m just talking out of my @$$. I have no idea…
I did save the info you provided to me earlier on the wheat grain lamp as a test, but haven’t explored that avenue yet. Would a 60mA lamp work? I found 60’s on Amazon with 2 day delivery, but the 50’s would take several weeks to get here. Since I have the relays already, and the personnel with the capability to swap them out, I had considered doing that first.
In the case of the test you suggested, wouldn’t a crank or cam sensor throw a code if they weren’t working. I guess the ultimate question is which of these possible causes would only present themselves under cold-start conditions? All of them?

 

Jeremy- What you are describing sounds more like a leaking injector problem. Mine had symptoms exactly as you described. The leaking injector(s) drips fuel and the resultant rich mixture results in a stumbling start. Once that fuel is burned, second or warm starts work perfectly. Having the injectors cleaned and resealed completely eliminated the problem in mine.

 

I do recall seeing someone mention that during my research. While I can’t comment with any authority, it feels like a whole bank is down on my car, with stumbles going deep enough to feel like it’s about to bog down and stall at some points. I suppose it’s not impossible for all 4 injectors on one side to be leaking and causing the sensation of a single-bank start. I should also mention, the one and only time the rough start left codes behind (but no CEL), the codes were P0300 to P0304: Multiple Misfire Recognition, then Major Emissions for Cylinders 1-4. This was the only time a rough start left codes in its wake. Never before or since.

 

Also, Terry, do you remember where you sent your injectors for service? Or is there a shop that FChatters frequent for this service nowadays?

 

I think that would be near enough. I guess the point of using a lamp with a value around 50mA is to simulate the relay coil impedance. This won't generate a fault in the ECU for a failed relay coil... and it won't burn out the ECU internals by drawing a lot of current. Modern ECUs should be able to handle higher, but I wouldn't go much above 60mA.

In summary: Lamp lights, immo ok. Lamp doesn't light.... could be a few things.

 

I had similar startup stumbles with my 612… 2 doses of injector cleaner and problem solved.

It’s a cheap and easy thing to try.

Bill

 

The same problem with my 360 was fixed by a new battery.

 

RC injection in CA would be my choice

 

I’ve done multiple bottles of injector cleaner by now. I always do one with my annual fluid change, but I think I’ve done 2 bottles of Chevron Techron now in the last month or two. No change. And I drive my car, too. 4 days a week, every week. Full warm-up cycle to proper temps, and then WOT bursts as God intended

 

In the last 3.5 years, I replaced the battery it came with with a new AGM battery. Last October, I installed an AntiGravity Lithium Ion battery. The AG has been a great addition, and while the cold start stumbles disappeared for the winter, they returned in May. Voltage remains stable and healthy across the board.

 

The fact that winter was better definitely points to more fuel at startup ..I would try a stronger bg44 first and see any difference..

 

Incidentally, I have 1 or 2 cans of BG44 sitting in the garage.
So you’re in the camp of suspecting clogged or leaking injectors? What is about the warmer weather that would cause the leaking injectors?

 

The colder weather needs a richer fuel mixture to run probably ..so when it is cold a a little extra fuel is not noticed

Just a SWAG

 

So, Jaymac, if its old sticky relays how come when I was at 360 school in 1999 in Maranello Ferrari even commented on it being very common?
In all those years the only commonality between cars that do it are weak battery voltage and just sometimes new batteries eliminated it for a while.
Executing some VooDoo fix on the immobilizer with zero supporting evidence does not seem like a good idea.

If you start it and it stumbles shut it right back off and restart.

 

Interesting. Food for thought. The BG44 will be easy enough. Swapping relays will be less than a few hours, mostly driving time to the shop. Cleaning the injectors would be the most time consuming between R&R, shipping there and back, and labor time. I’ll probably start with local projects first, and work my way up the downtime-based list.

 

Brian, that’s crazy to me that it was already an issue way back in 1999 when the car was released, and Ferrari knew about it the whole time and didn’t fix the root cause. Crazy!

When they were telling you guys to install additional ground straps from the ECU cases to the engine blocks, did that have any effect on cold-start issues?

With the Antigravity battery, the resting voltage never drops below 13.1, even with 5 days or more in between starts. Leads me to believe that it’s not specifically a voltage issue.

I have done the stop and re-start technique in the past. Only once did it stumble the second time as well.

What’s your opinion on the leaking/dirty fuel injectors causing extra fuel to be dumped at startup, causing the stumble?

Thanks!

 

Nothing crazy about it. Every manufacturer releases cars with known minor issues all the time.
No.
I disagree.
No.

 

I respect and appreciate your succinctness and concision.
Thanks!

 

Jeremy- Here you go. Same thing josh recommended.


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I fixed my cold start issue by replacing the secondary air pump relay. I noticed that on the first start from cold, the secondary air pump would not turn on (got someone to start the car for me while I stood at the back with the engine cover open). Second crank and the pump would engage. Replacing the relay resulted in the pump starting first time and no more cold start problems.

Prior to discovering this I'd had injectors cleaned, replaced every vacuum hose (which it needed anyway), cleaned the MAF sensors and checked for air leaks everywhere.

 

Interesting. Worth a look!

 

I had the same issue,
Bad Stumble on cold start up, turn it off, turn back on and it's just fine. No codes.
I chased around so many unrelated things such as fuel injectors etc.

Turned out just a mass air flow meters needed to be replaced.

Good luck.

 

I’m ultimately hoping for a simple fix, if one exists. Plugs, MAF’s and primary O2’s were all replaced in 2023 with the Trev tune.