So, I recently bought an A610.
The seller told me it had 'the cutting out issue' before I picked it up, and on a brief test drive all was fine. I handed over my money and immediately I left him the car cut out about 5 times in the first mile! Brilliant.
Over the last couple of weeks ive learned quite a lot and have decided that my issue is probably different to some others. I suspect there are many root causes out there that all lead to the same final result. The ECU being put into an error state and shutting down the engine. Power cycling the ECU clears the fault, it runs again and then trips with the same fault.
My particular cutting out issue is clearly related to heat and engine load. From stone cold the car is absoloutely fine. So long as you keep moving it remains fine. However, as soon as you have stopped for any length of time, or got stuck in traffic, and given the engine bay a bit of heat soak, then the next time you try to drive the car is initially almost undrivable, if you persevere and get some airflow into the engine bay it progressively becomes better and better. 10 mins on the motorway at low load (low heat!) and high speed so some air gets wafted about and the car is robust again.
Also, once you are in a situation where things are hot and its cutting out regularly, it will only cut out when you apply slight load. It will idle fine, and rev fine, but as soon as you load the engine to drive the car it will cut. Also, as you start to cool the car again by driving, the load you need to apply to cause the engine to cut increases. Its actually really quite predictable in when it will cut out.
At the moment my engine bay cooling fans are not working, however in only 1.5miles of normal driving this morning from cold (totally trouble free), it was enough to make it cut out 6 times on the 1.5 mile return journey. I have added a few thermocouples into the engine bay to read the temperatures we are talking about and in the region of the engine bay fan switch sensor by the turbo were only at an air temp of about 60 degrees, long before the fans would have kicked in and the problem is already very apparent.
I've read in some detail all that has been discussed before regarding this issue. I have added a ground to the fuel pump relay. No change. The ECU is also not over heating as the problem is no different with the ECU laid out on top of the trans tunnel. The relays them selves are not hot either. I think the previous owner had tried to add the ground wire for the relay too, but seen as he'd added it to the AC compressor relay it hadn't had the effect he was after either.
Other things I have tried:
I've tried to override the 12V side of the switching wires at fuel pump relay but figure I must be backfeeding 12V somehow as the whole car switches on! (not hard to hotwire a 610 then!). Ive not actually tried to drive in this state but I'll try that soon I think.
I'd read about lambda sensor issues and damage to the wiring on a car causing issues when the car is hot, so I've inspected all my wiring and found no clear fault. I've also driven with the signal wire for the lambda disconnected (left the two heater wires connected though) and the problem remains.
Im also aware that my car is missing a heatshield over the CAT that I can see present in the manual, with the coil pack mounted above it I wondered it it was getting too hot when the engine bay was allowed to heatsoak so I put a thermocouple on that too, but the problem is clear at only about 50 degrees on the coil casing so I cannot see that it the issue.
It seems clear to me that there is a fault state that the ECU is encountering once its been hot in the engine bay. And that this fault state is also related to engine load, as it only when under some load (and not even very much actually) that it will stop.
Its also important to state that the cut out is sharp and immediate, it is the ECU cutting Inj or Ign. It is not simply the fuel pressure dropping as a result of the fuel pump being turned off. Unless there is a fuel pressure strategy in the ECU that will cut Inj or Ign in the event of a drop in fuel pressure? I remember my 200SX used to stop in the same way if you ran it so low on fuel that it surged while driving hard to look after itself and not run lean on boost. (though it came back itself when the fuel pressure was good again) Does an A610 do something similar?
My next steps are to try and run it with various (presumably non critical) sensors disconnected. If I find one that with it disconnected it runs without cutting out, even if it runs like a bag of nails, then its the next place to start looking. (Will it run without TPS, or the temp sensor in the throttle body for example? - ill be able to let you know soon!)
This is a long one I know so thanks for reading. Any thoughts would be warmly welcomed.
If anyone has a picture of the wire they grounded that might help. Trial and error showed me the relay controlling the fuel pump was not the one it claimed to be in the car manual! I'm pretty sure I got the right one, but best to be sure - even though im thinking less and less that grounding the fuel pump switched ground is going to help my particular cut out issues.
I'll try anything though!
Cheers all.