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Hey all, I'm struggling with the high-load stumble issue and have been for about a year. Same old symptoms: missing and hesitating on the highway under load at 2000 rpm up. This happens at both part and full throttle.
I've done plugs and coils. Earlier this year, I did the walnut blast. I've run Techron. Nothing works particularly well.
So. the car's been at the dealer for a couple of weeks. I asked them to look at the problem. They found a fault on the low-pressure fuel sensor and replaced it. After doing a smoke test, they replaced one of the turbo dump valve assemblies. Got the car back and no joy. It still had the problem.
Brought it back to the dealer and took the shop foreman for a ride. He ended up over the next few days replacing all the injectors and HPFP. He pulled the O2 sensors and checked that the cats were not blocked. He pulled the intake manifold and verified the intake ports were clean. He swapped plugs and coils to check to see if anything followed the changes, but no problem was found.
I got the car back tonight and it, frankly, is worse than when I brought it to them. Talking to the foreman, he was at a loss. His next step would have been to replace the engine wiring harness, then the DME if the harness swap didn't work.
I've seen issues with the MOSFETs in the DME, but don't think they fail gradually. If they did, this could be the source of the problem, but I really doubt it. Has anyone seen a harness failure? If so, what fails?
The car has barely 90k miles on it and hasn't been abused. Any thoughts are appreciated.
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