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reduce acceleration, hard acceleration may damage catalyser

13K views 16 replies 5 participants last post by  scellpt 
#1 ·
hi all, just had the message

reduce acceleration, hard acceleration may damage catalyser. Any ideas what the problem is. The car is a 2002 745i with 80k on it.

i did have a mis-fire a few weeks ago but stopped the engine and turned it back on again and it was fine?

any ideas?
 
#2 ·
Have you checked to make sure all the coils are plugged in? have you recently change the spark plugs? do you have access to a OBD code reader?
If the first two arent true, if you can get to an OBD get the codes read out, find out what cylinder the misfire is, take the coil out and swap it with another cylinder's coil, if the code moves to the cylinder the coil was moved to then the coil is bad, if not check the spark plug in that cylinder and wire connections to the cylinder. matter of fact no matter what always make sure the coil is seated properly and that the plug into the coil is seated properly just incase you move the coil and then the code moves.
 
#3 ·
thanks for that mate, I had a similar issue some years ago with an audi s8 but as the 745 is a lot more technical i wanted to check. Dont have any electronics to test but I will get a mechanic to check the plugs next week. I did have the rocker cover gaskets changed a few weeks ago so that might have disturbed something!
 
#4 ·
Coils
 
#5 ·
And now the real repairs begin at 80,000 miles.
 
#7 ·
Yes it still happens and now more frequently but only when cold . Now every morning the check engine light comes on together with the message. But it goes off in 1 or 2 minutes. However a week ago the check engine light stayed on . For days until I used my machine and cleared the codes however the code reader said number 5 cylinder misfire. So cold ain't check nothing yet . So when I get a break in a week or so I will report back.

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#8 ·
Today I checked the coil still saying misfire cylinder 5 after I swap the coil with number 6 . I notice that number 6 had oil in the plug holes that was rotting out the rubber on the coil pack so I just did my best to clean it up and put back together . I work early so it will be cold in the morning so will c if any changes.
In the mean time any suggestions

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#11 ·
Thanks everyone, the problem is fixed. When we lifted the passengers front carpet we noticed it was wet. We checked all drain holes and they were clear (even the ones under the bonnet). In the end it was the water hitting the electrics under the passenger floor, we replaced the windscreen and hey presto, never happened again!
 
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