All,

I have a 2023 P400 MHEV Defender 110. Over the past, say, 6 months, I've noticed that under load (acceleration), I will sometimes have the engine torque cut and then re-engage within a second or so. This is sometimes (most times) accompanied by an audible "puff of air" sound from the rear of the car (48v battery area?). There are no codes, I've had it to the dealer once where they could replicate it but had no information on it and, as I said, there are no codes. It feels like the system is loosing boost for a brief second, kind of like a blow-off valve issue but I honestly have no idea. The sound from the back has me thinking perhaps the electric supercharger is drawing too much current and the 48V battery cooling system is is having an issue, but again, purely speculation.

Has anyone else experienced this? Any suggestions?

TIA - Scott

 

I'm not sure that the air sound and the power cut are related. The compressor for the air suspension lives in the rear and will makes a puff sound every now and then while driving. To hear a puff of air from a blow off valve would imply an external wastegate, which you're never going to see on a car from the factory for emission reasons. That's a Japanese tuner car thing. Unfortunately our local dealer sucks at diagnosis.

I'd vote for either the engine cutting timing or, if this only happens while accelerating during cornering while the fuel tank is low, fuel cut. I don't know exactly how the Defender manages timing, but I'd consider disconnecting the battery ground for a few minutes so that it relearns (move passenger seat all the way forward, pull the panel under it, need a 10 mm wrench). Possible it learned some bad habits after a bad tank of gas.

- Fellow P-car owner in ABQ

 

Thanks for your comments. Sorry I wasn’t as clear as I should have been. My understanding is that the 48V lithium battery is “air cooled” and perhaps under extreme current draw, there could be something with the air cooling that I was hearing.

re: the waste-gate analogy, that was just a comment for how it feels. These engines also have a turbo and perhaps there is a leak or a hose that is collapsing under boost (I did have a turbo Subaru once that had an issue with a collapsing inlet hose that had a similar feel)? Again, just guessing.

 

When I have experienced this, it is certainly the traction control engaging. There is an off ramp that feeds into a 4 lane road near my house and making a left turn into traffic often requires full power. After a couple of chirps coming from the front right tire, I can feel the power cut out to slow me down and keep me on the intended path. This is especially true with the OEM Goodyear tires. (Not as much right now with wider and grippier Nokian winter tires)

 

Thanks for your comments. Pretty sure this is power train related and not traction control as I never have any sign of traction loss and it doesn’t “feel” like traction control. It’s as though the engine just “coughs” for a second and then back to normal.

 

Sounds pretty maddening. I had a situation with power loss last month, and it was sporadic, but prolonged. Turned out the oil filter hadn't been tightened enough after the recent change and had spun off enough to start leaking oil. The P400 eventually shut down and would restart but immediately die. It cost the Euro shop that did the change prior to my trip about $4k because by the time it was a problem I was 1800 miles away from home in SE Bumble, Utah. But the truck is fine again now.

Maybe some sort of vacuum leak, or collapsing vacuum hose under WOT in yours? (Also a serial Porsche sportscar owner. 22 years ago I passed on a stunning Prussian Blue/Cork '87 930, a beautiful example with under 30k miles, because I found the experience to be less satisfying than a same-generation 3.2 Carrera, owing to the lag and the 4-speed. They say never meet your heroes.)

(But not to worry; subsequent water-cooled Turbos did the trick!)

 

Hey 930dreamer did you ever get this figured out?

My 2025 with 2k miles started experiencing this exact same issue about 300 miles ago and I finally dropped to the dealer last night because it was getting worse.

My head is also leaning to fuel, air, issue, or some sort of inlet pipe being restricted.

 

yes - it finally got bad enough that it dropped a cylinder so I managed to drive it to the dealership (I wasn’t too far away when it happened). The reported cause was a stuck fuel injector. New engine and about 2 months separated from my defender lol.

 

Thanks for the reply - definitely not what I was hoping to hear lol. Is there a reason they had to go full engine replacement? Was there damage to the cylinder from the stuck fuel injector vs just replacing the injector? How did they determine the issue?

Mine has thrown no CEL’s or error codes…

 

I never had any CEL or codes either - until the cylinder dropped and then I did get a flashing CEL. I believe they did a compression test and determined the issue. They were a little short on specifics but I was told by a knowledgeable mechanic that a stuck (open) injector can flood the cylinder which could wash out all the oil lubrication and seize the piston. I am not an expert by any means.