Hi Everyone - I've been hunting down various issues on my M5 to try and help the low RPM stumbling feeling + vibrations at 2.5k-3k RPM (UK motorway speed in 6th).
So far I've updated just about everything in the drive train inc the flywheel and clutch last week. Surprisingly I now have a super light clutch as the throw out bearing was very tired indeed and wearing the gearbox shaft cover tube away. The issue has not actually helped the vibration as the new dual mass flywheel is less 'loose' that the old one so i'm still hunting!
One of the areas I've been meaning to look at was getting my fuel injectors cleaned & refreshing the seals - I've known others who have said this has helped their cars, especially in the case of high mileage vehicles like my M5 which is almost at 130k miles. I've always used quality Shell V-Power fuel in the car since I've had it (18 months) however it has 10 previous owners who'd not necessarily been quite so fussy. Anyway to this aim I decided to remove the injectors and send them away for professional cleaning as I had a weeks holiday where the car could sit on the drive.
So - back to fuel injectors - I searched around the forum and found minimal content and no DIY which surprised me so I decided to share my learning's for the benefit of others who may wish to do the same. I've found so much of the content on here useful I wanted to try and fill a gap in the DIY section for others. I've included lots of pics and borrowed some others - these have been marked to show non-M5.
Searching the net I did find one item on another forum which was a useful reference:
https://www.bimmerfest.com/forums/showthread.php?t=571302
Doru on Bimmerfest has completed an injector removal and replacement on a 6 cyclinder petrol Beemer - though their's is not an M5 and the injectors are Siemens units - there are similarities between the models with the holding clips and the electrical connection clips. I've borrowed several of the pics (so they continue to work on this board) and linked above to their item which I found most useful as a reference + their pictures were way better than mine!
One item to note is their were various models of injectors used on the M5 - if you are looking on RealOEM then you ideally need to use the last 7 digits of your VIN to help it select only the relevant items. The early Siemens units used in some BMW's of this era have a known issue where they swell and leak internally over time - I'm not sure if these units are used on M5's but something to be aware of.
RealOEM fuel injector info can be found here - my car is a 2002 UK model and uses the Bosch injectors shown in the last picture.
RealOEM link: RealOEM.com Â* Diagram Selection
Remove fuel relay module and / or fuse / or Battery. Once this lot ius removed the fuel rails will be open so you do NOT want the fuel pump running at all. Remove air intakes, Plenum cover, Plenum itself. Remove cabin air intakes if you need the room. Once that lot is removed it should look something like this:
![Image]()
I removed the plenum to throttle body gaskets - it may be possible to remove the injectors without however it only takes a few minutes to do - undo the band straps under the gasket around each throttle body - there is just enough access. Carefully pull up evenly above each throttle body and the rubber gasket will slide up and off.
![Image]()
![Image]()
Once removed it'll expose each throttle body and give you more room to fight with the next bit. Wet patches on my clamps is just where I put some 3-in-1 on them to ease re-installation.
![Image]()
Now we need to release the electrical connections to the injectors. It seems others have said you simply need to pull firmly upwards along the rail and the connectors will un-clip. I found this not to be the case and would have broken something expensive if i'd tried even harder! I used the technique Doru used on Bimmerforums and partially un-hooked the connector springs - this allowed the connectors to then release and lift up an centimeter or 2. Note access to the rear connectors is much more difficult but doable - if the injector > fuel rail clips are in the way they can be rotated around if necessary. Eventually and after much muttering I managed to release the electrical connections - others have had trouble with breaking / bending the connector springs, I didn't though and they simply popped back into place afterwards. Should you break one completely it was suggested on another M5Board posting I read to use zip-ties to secure the electrical rail down to the injectors by tying around the fuel rail. It's all very solid so should work fine. Note the next 2 pics are NOT from an M5...
![Image]()
![Image]()
These pics are not the clearest but should give you an idea what to expect. I used an iphone only as oil, petrol and expensive DSLR's don't really mix in my book with one person doing the job.
![Image]()
![Image]()
![Image]()
Next step is to remove the injectors from the car - I found mine were pretty solid and again to avoid breaking anything I decided to remove the fuel rail from the injectors first, then remove each injector at a time from the inlet manifold. To do this you remove the 2x 10mm bolts holding the rail down, then lever out the injector securing clips like below (again pic is not M5 but clip is identical:
![Image]()
Be careful doing this - the clips have a habit of flying off - I lost two - glad I ordered 8x replacements - they were 40p IIRC so dirt cheap.
If you now pull upwards on the front most injector on the rail it should pop off. Expect some fuel to pour out so have a rag underneath to catch it. Work along the rail until they are all undone. 2 of my injectors came out of the inlet manifold instead of the rail. Either way they will all come off - any left in the inlet manifold can be removed by pulling them - I found it helped to twist them a little and wiggle them out.
![Image]()
Once all the injectors are removed the fuel rail can be lifted out of the way while you clean up the injector holes in the inlet manifold - don't strain the rubber connecting hose. The upper seals will most likely still be in the fuel rail and can be removed (hook them out) if you are replacing - mine looked in great shape.
![Image]()
![Image]()
One rail down - another to go. Once completed I had 8 removed injectors - they looked a little sorry for themselves externally however the 4x tiny holes inside the tips looked very clean. The oily gunge is I believe from the crankcase ventilation oil. The inlet manifold holes they were pulled from were also slightly oily and I cleaned these with throttle body cleaner and swabs.
Note the lower seals are very gunked up - these are air seals only and seem to attract the dirt - remember though these are from a 130k mile car and nothing in the service history says they've been touched before. I'm hoping a clean and refresh in this area may aid my search for smoother low revs running alongside the cleaned injectors in case any un-metered air is leaking by (minimal chance I know!).
![Image]()
Note the very end is clean - I assume this is because some petrol blows back and keeps it clean:
![Image]()
A word on the seals. I removed the lower seals as I wanted to clean them and possibly re-use if in good condition. Your now thinking what a tightwad, however read on - I initially thought 'replace the lot, they'll be cheap', then I looked up BMW's UK prices... madness is perhaps the best way to describe these seal costs. As of today (April 2014) Upper fuel rail seals for my car are just over £4 each (not too bad I suppose compared with usual M5 bits) and the lower ones are, wait for it, £12.20 each. For an o-ring! So over £130 for 16 seals... hmmm. Anyway I looked up and ordered a selection of viton seals near the size listed on RealOEM for the lower seals (9,3X2,62) - £0.24 each.
![Image]()
![Image]()
The seals I removed cleaned up well and appear in good condition - I may re-use, will compare with the online order of non-BMW seals when they arrive. As of now my injectors are about to wing their way off to a UK company to clean & test. They provide new upper seals, new filters and a report showing flow rate, resistance etc etc. Testing and shipping for all 8 is £107 which seems reasonable.
Re-installation is the reverse of removal to quote a well known car maintenance manual - I will be inserting the injectors into the fuel rail first then push them 4 at a time into the inlet manifold. Then resecure the electrical connectors with a small push down once aligned. Don't forget to bolt down each rail first. Once they are in (both rails!) it's very important to replace the fuel relay / fuse and prime the fuel pump a few times by turning key to position 2 - don't start the car yet. Now check for leaks around the fuel rail to injector seal area. If it's all good try starting the car - it'll probably run pretty rough as the air metering will be all over the place with no plenum and MAFs in place. Start the car and hunt for leaks between the rail and the injector. Be careful nothing gets in the throttle bodies or near them if revving the engine. I suggest run the engine briefly then switch off and again check for leaks.
I'll update this once I receive them back with my findings - even if it does not help my initial issue it's a worthy PM I think given the miles.
If anyone has any questions, comments or feedback please feel free to ask. First time doing a DIY type post so open to any comments.
Simon
So far I've updated just about everything in the drive train inc the flywheel and clutch last week. Surprisingly I now have a super light clutch as the throw out bearing was very tired indeed and wearing the gearbox shaft cover tube away. The issue has not actually helped the vibration as the new dual mass flywheel is less 'loose' that the old one so i'm still hunting!
One of the areas I've been meaning to look at was getting my fuel injectors cleaned & refreshing the seals - I've known others who have said this has helped their cars, especially in the case of high mileage vehicles like my M5 which is almost at 130k miles. I've always used quality Shell V-Power fuel in the car since I've had it (18 months) however it has 10 previous owners who'd not necessarily been quite so fussy. Anyway to this aim I decided to remove the injectors and send them away for professional cleaning as I had a weeks holiday where the car could sit on the drive.
So - back to fuel injectors - I searched around the forum and found minimal content and no DIY which surprised me so I decided to share my learning's for the benefit of others who may wish to do the same. I've found so much of the content on here useful I wanted to try and fill a gap in the DIY section for others. I've included lots of pics and borrowed some others - these have been marked to show non-M5.
Searching the net I did find one item on another forum which was a useful reference:
https://www.bimmerfest.com/forums/showthread.php?t=571302
Doru on Bimmerfest has completed an injector removal and replacement on a 6 cyclinder petrol Beemer - though their's is not an M5 and the injectors are Siemens units - there are similarities between the models with the holding clips and the electrical connection clips. I've borrowed several of the pics (so they continue to work on this board) and linked above to their item which I found most useful as a reference + their pictures were way better than mine!
One item to note is their were various models of injectors used on the M5 - if you are looking on RealOEM then you ideally need to use the last 7 digits of your VIN to help it select only the relevant items. The early Siemens units used in some BMW's of this era have a known issue where they swell and leak internally over time - I'm not sure if these units are used on M5's but something to be aware of.
RealOEM fuel injector info can be found here - my car is a 2002 UK model and uses the Bosch injectors shown in the last picture.
RealOEM link: RealOEM.com Â* Diagram Selection
Remove fuel relay module and / or fuse / or Battery. Once this lot ius removed the fuel rails will be open so you do NOT want the fuel pump running at all. Remove air intakes, Plenum cover, Plenum itself. Remove cabin air intakes if you need the room. Once that lot is removed it should look something like this:
I removed the plenum to throttle body gaskets - it may be possible to remove the injectors without however it only takes a few minutes to do - undo the band straps under the gasket around each throttle body - there is just enough access. Carefully pull up evenly above each throttle body and the rubber gasket will slide up and off.
Once removed it'll expose each throttle body and give you more room to fight with the next bit. Wet patches on my clamps is just where I put some 3-in-1 on them to ease re-installation.
Now we need to release the electrical connections to the injectors. It seems others have said you simply need to pull firmly upwards along the rail and the connectors will un-clip. I found this not to be the case and would have broken something expensive if i'd tried even harder! I used the technique Doru used on Bimmerforums and partially un-hooked the connector springs - this allowed the connectors to then release and lift up an centimeter or 2. Note access to the rear connectors is much more difficult but doable - if the injector > fuel rail clips are in the way they can be rotated around if necessary. Eventually and after much muttering I managed to release the electrical connections - others have had trouble with breaking / bending the connector springs, I didn't though and they simply popped back into place afterwards. Should you break one completely it was suggested on another M5Board posting I read to use zip-ties to secure the electrical rail down to the injectors by tying around the fuel rail. It's all very solid so should work fine. Note the next 2 pics are NOT from an M5...
These pics are not the clearest but should give you an idea what to expect. I used an iphone only as oil, petrol and expensive DSLR's don't really mix in my book with one person doing the job.
Next step is to remove the injectors from the car - I found mine were pretty solid and again to avoid breaking anything I decided to remove the fuel rail from the injectors first, then remove each injector at a time from the inlet manifold. To do this you remove the 2x 10mm bolts holding the rail down, then lever out the injector securing clips like below (again pic is not M5 but clip is identical:
Be careful doing this - the clips have a habit of flying off - I lost two - glad I ordered 8x replacements - they were 40p IIRC so dirt cheap.
If you now pull upwards on the front most injector on the rail it should pop off. Expect some fuel to pour out so have a rag underneath to catch it. Work along the rail until they are all undone. 2 of my injectors came out of the inlet manifold instead of the rail. Either way they will all come off - any left in the inlet manifold can be removed by pulling them - I found it helped to twist them a little and wiggle them out.
Once all the injectors are removed the fuel rail can be lifted out of the way while you clean up the injector holes in the inlet manifold - don't strain the rubber connecting hose. The upper seals will most likely still be in the fuel rail and can be removed (hook them out) if you are replacing - mine looked in great shape.
One rail down - another to go. Once completed I had 8 removed injectors - they looked a little sorry for themselves externally however the 4x tiny holes inside the tips looked very clean. The oily gunge is I believe from the crankcase ventilation oil. The inlet manifold holes they were pulled from were also slightly oily and I cleaned these with throttle body cleaner and swabs.
Note the lower seals are very gunked up - these are air seals only and seem to attract the dirt - remember though these are from a 130k mile car and nothing in the service history says they've been touched before. I'm hoping a clean and refresh in this area may aid my search for smoother low revs running alongside the cleaned injectors in case any un-metered air is leaking by (minimal chance I know!).
Note the very end is clean - I assume this is because some petrol blows back and keeps it clean:
A word on the seals. I removed the lower seals as I wanted to clean them and possibly re-use if in good condition. Your now thinking what a tightwad, however read on - I initially thought 'replace the lot, they'll be cheap', then I looked up BMW's UK prices... madness is perhaps the best way to describe these seal costs. As of today (April 2014) Upper fuel rail seals for my car are just over £4 each (not too bad I suppose compared with usual M5 bits) and the lower ones are, wait for it, £12.20 each. For an o-ring! So over £130 for 16 seals... hmmm. Anyway I looked up and ordered a selection of viton seals near the size listed on RealOEM for the lower seals (9,3X2,62) - £0.24 each.
The seals I removed cleaned up well and appear in good condition - I may re-use, will compare with the online order of non-BMW seals when they arrive. As of now my injectors are about to wing their way off to a UK company to clean & test. They provide new upper seals, new filters and a report showing flow rate, resistance etc etc. Testing and shipping for all 8 is £107 which seems reasonable.
Re-installation is the reverse of removal to quote a well known car maintenance manual - I will be inserting the injectors into the fuel rail first then push them 4 at a time into the inlet manifold. Then resecure the electrical connectors with a small push down once aligned. Don't forget to bolt down each rail first. Once they are in (both rails!) it's very important to replace the fuel relay / fuse and prime the fuel pump a few times by turning key to position 2 - don't start the car yet. Now check for leaks around the fuel rail to injector seal area. If it's all good try starting the car - it'll probably run pretty rough as the air metering will be all over the place with no plenum and MAFs in place. Start the car and hunt for leaks between the rail and the injector. Be careful nothing gets in the throttle bodies or near them if revving the engine. I suggest run the engine briefly then switch off and again check for leaks.
I'll update this once I receive them back with my findings - even if it does not help my initial issue it's a worthy PM I think given the miles.
If anyone has any questions, comments or feedback please feel free to ask. First time doing a DIY type post so open to any comments.
Simon
