Revs rise when braking FIXED FIXED!

Timmo478 · Post by **Timmo478** » Thu Jun 13, 2019 6:13 pm

Yeah get where u comin from but don't really wanna do that. Would rather waste 10 or 20 quid having it tested.

roesroyce · Post by **roesroyce** » Thu Jun 20, 2019 10:20 pm

My 2.5 did the same was scratching my head then realised the maf electrical plug wasn't plugged in all the way !
Plugged it in all the way and hey presto sorted.
Check your maf electrical plug may be plugged in correctly but may have a loose or broken connection inside the plug itself.
Hope you get it sorted .

Timmo478 · Post by **Timmo478** » Fri Jun 28, 2019 8:05 pm

Slight update. Made my own YouTube smoke detector and smoke tested her. Only leak I found was out of the centre of the upgraded (which I now regret) disa valve bolt. Which made me realise that if you look at how these upgrade bolts work, there is no seal on the bolt head, thus allowing for a vacuum leak. As i mentioned previous, the only 2 things I've touched are the disa and the MAF removal for the disa. With the car running I put my finger over the disa valve bolt and it gets sucked to it enough to leave a round mark on my finger. However having found this vacuum leak my engine revs still rise on braking when I cover the bolt head with my finger. I read somewhere that if u look at the inside of the intake disa valve area with disa removed its actually shaped to stop the standard pin coming out all the way. So for your disa pin to destroy an engine, the disa valve would have to completely break into pieces to allow the pin out. Looks like I'm going back to a standard disa as I ain't forking out for another, different upgrade kit. Will keep u guys posted.

Timmo478 · Post by **Timmo478** » Fri Jul 12, 2019 5:10 pm

SOLVED..... Was the MAF sensor after all guys. Just changed it out and no more issues. Removed the vacuum pipe at the 1 way valve and blocked both off and it still occurred.
The clue to it being electrical and not vacuum was also if we pressed the brake slowly, the revs went up the instant the brake lights came on.
Cheers for all the advice.

ph001 · Post by **ph001** » Fri Jul 12, 2019 5:16 pm

Power of the forum

. I can’t imagine a garage would have ever linked the two.

Timmo478 · Post by **Timmo478** » Fri Jul 12, 2019 7:39 pm

Absolutely right. And if a garage ever did put the 2 together, would hafe cost the earth just for the diagnoses.
Up the forum

Magsy · Post by **Magsy** » Fri Aug 16, 2019 11:39 am

To add to this I had the same issue with braking causing revs to rise. Checked the MAF and it was dead, replaced and all resolved.

Thanks.

wonkydonkey · Post by **wonkydonkey** » Fri Aug 16, 2019 2:59 pm

The power of a good forum!

Happy for you both!

Ruofdez · Post by **Ruofdez** » Fri Aug 16, 2019 3:11 pm

Was this an issue for you once the engine warmed up or only when cold? I've been having a similar issue. Already replaced the MAF once but with a second hand unit. Will be speaking to BMW garage later about returns policy on new maf should it not be the issue but expect the price will be eye watering.

My Issue - viewtopic.php?f=3&t=114741

Magsy · Post by **Magsy** » Wed Aug 21, 2019 8:12 am

For me in an auto, it went away mostly when warm but was still present (foot on brake at lights etc)

I did a lot of diagnosis, I even created a new wiring harness from MAF to ECU. I bought two MAFs, one Hella and one VDO because of the situation you are in now not trusting it...

After all the s**t I learned using simple OBD tool with something that can read MAF values on my phone was easiest (In my case OBD Link MX)

Doing this at least in my case it was clear, the MAF was reading 0, or it was working for 5 miles then not etc

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