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Long-term review

BMW M635 CSI - long-term review

Cheaper than a kitchen
Published: 20 Mar 2020


  • SPEC

    BMW M635 CSi

How easy is it to fix an ECU on an old BMW M635 CSi?

If the coronavirus could be transferred between cars, my garage may as well be called the Wuhan Automotive College. No amount of hand sanitiser could’ve prevented this pandemic; it’s taken me a solid 31 years of terrible car buying to reach this point.

The epicentre lies firmly with the Asian corner of the garage. My R34 GT-R needs a new cylinder head and the RX-7 a whole new rotary engine. Having acted relatively fast, the German corner avoided full quarantine in the form of a new boot release (E61 M5) and new exhaust valve (S600 AMG). 

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The M635 CSi has been back under the knife this month, though fortunately not served up as soup. It is riddled with a virus, however. Thanks to leading surgeon Ron Kiddell from RK Tuning in Essex, it turns out the BMW’s issue is down to a faulty ECU. 

Thanks to Ron’s heroism, I’ve been able to self-isolate from the comfort of my own home; a proper result seeing as I’ve run out of parking on my driveway. 

Unsurprisingly, it’s quite difficult to find a new ECU for a car they only made 4,088 examples of some 30-plus years ago. The solution? One of two avenues. The first (and most affordable) is to send off the ECU to be remanufactured – the mask and washy hands approach. The second involves replacing the ECU in its entirety for a standalone system such as Omex or MoTeC – expensive and time-consuming, but with the added bonus of vastly improving the engine’s running and preventing the issue from reoccurring. Basically, getting on a flight to Antarctica for the next few months. 

For the time being I’ve chosen the easier route, given the initial diagnosis pointing to water ingress as opposed to a complete ECU failure. But if that doesn’t work – because it inevitably won’t – it’ll be full lobotomy time. Assuming the world hasn’t descended into an episode of The Purge controlled by Andrex CEO Tristram Wilkinson.

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