A HEAD SCRATCHER - SOLVED

[Larz]

Just thought I would share this with you lot.
I recently got my new DRLs from Osram, the new Osram CBI headlamps, and new fog lamps and bulbs. I am in the process of installing these now and will post pics when finished.
So ... I wanted to remove my existing Phillips daylight-8 DRLs. I loosened the NEG and POS terminal connections on the battery to slde out the tabs for the DRL controller. I only loosened them just barely enough to slide out the metal tabs, I did not remove or lift the actual battery cables from the battery itself. I removed the rest of the wiring and the actual DRLs forom the bumper.
Next, I removed both front wheels to install my Osram CBI headlamps and replaced the wheels. A this point, I got a call on my mobile from a mate who was setting up a rugby match on the beach in about an hour and he wanted me to play center for his side. I dashed into my house, got my kit on, and was off to the match.
As I pulled out of my driveway, I noticed the car was not accelerating normally - almost as if there was resistance in allowing the car to move forward. I reversed back into the driveway and it acted normal, but every time I went forward, again with the resistance. It was as if the brakes were not fully disengaged. I could not work out what could be wrong! I feared I did something when I removed / replaced the front wheels but that seemed impossible. I did nothing to the rotors or the brakes - just the wheels. I had no CEL showing.
While I sat there trying to work it out, I remembered seeing many posts in here where the member posted a problem and they were told to check the battery connections. I was 100% sure that was NOT the problem, but I checked the cables and they were not very loose, but I was able to slide them side to side because they were still slightly loose from removing the DRLs. I tightened them as I was not going to have time for rugby AND do the rest of the DRL and fog light install.
I decided I would drive to the match in my Fleetwood and leave the M at home. I had to move the M well away from the garage to make room to drive the mammoth fleetwood out (its a 1968 and nearly 20ft long).
As I drove the M out the way, BAM! it was completely normal again! It accelerated normally with no resistance and I was gob smacked! The trouble was a slightly loose battery cable ?!?!?!?
I can see having VERY loose battery cable causing trouble with starting, or lights, etc. But a very slightly loose cable caused something in the car's computer (I assume) to prevent the car from driving normally.
Long story short .... again it pays to read the posts here, even if it's a topic that isn't relative to you.
BTW, our side won the match with a daring drive in the last few minutes between myself and two others, passing between us to make the try, then off to the Elbo Room for post-match convo, rugby songs, and Grolsch !

[06M4.5]

Great info Lars, thanks for sharing.

My cuzin just went 1 day giving her M35x a boost every time she needed to start the car, it was the NEG side of the battery not being tight enough.