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Help rough running car
Posted: Fri Aug 22, 2025 11:40 am
by Corasdad
I thought i had finished my m52 swap but today i started the car and more issues have happened ,when i start it it coughs and splutters and when i try to rev it it trys to stall and wont rev past 2000rpm,i have a very very cheap scan tool did a quickie and it showed camshaft sensor on bank a so i bought a brand new one for 140 and hoped this would be the fix, that code now doesnt come up which is great but it then brought up a fault code to injector 1 so i unplugged them all and firmly pushed them back in and that code has gone but still it made no difference to the rough running and i have no further fault codes can anybody suggest what to look for next, getting to the point i might just cut my loses
Re: Help rough running car
Posted: Fri Aug 22, 2025 2:20 pm
by Speedtouch
Have you ever seen/heard the engine running properly (i.e., when fitted in the donor car), prior to installing it?
Re: Help rough running car
Posted: Fri Aug 22, 2025 2:46 pm
by Corasdad
Yes it run fine b4, i took it for a drive the other day to get wheels aligned.
Re: Help rough running car
Posted: Fri Aug 22, 2025 2:49 pm
by Corasdad
Re: Help rough running car
Posted: Sat Aug 23, 2025 10:46 am
by Corasdad
Ivc cleaned and free moving still no change,its had new disa fitted new plugs new pcv fitted
Re: Help rough running car
Posted: Sat Aug 23, 2025 1:12 pm
by Speedtouch
Perhaps try refitting the old ignition parts, if you still have them - perhaps there's a fault with the new ones...
I saw this on an E39 forum:
"Most probably a vac leak somewhere. Check all the pipe work on the diags below. You can try running with the MAF disconnected briefly. The car should set itself to a basic state which will at least give an indication if the MAF is at fault."
https://www.bimmerforums.co.uk/threads/ ... pm.567189/
Re: Help rough running car
Posted: Sat Aug 23, 2025 2:41 pm
by Corasdad
My car runs with no maf anyway ,every time i plug it in it stalls the car so it stays unplugged for now until i can sort rest of the gremlins
Re: Help rough running car
Posted: Sat Aug 23, 2025 2:47 pm
by Corasdad
Found one vac leak, looks like rubber bung has come off
Re: Help rough running car
Posted: Mon Aug 25, 2025 5:38 pm
by Corasdad
Now showing injector circuit cylinder 1 is this likely a wire or bad injector
Re: Help rough running car
Posted: Mon Aug 25, 2025 6:23 pm
by Speedtouch
Good work. Ideally, use a multimeter to check for the HT lead(s) resistance and injector impedance. If you're using coil packs, try swapping them over between a pair of cylinders and see if the fault gets transferred...
Re: Help rough running car
Posted: Mon Aug 25, 2025 8:18 pm
by Corasdad
Yeah changed over 1 to 2 and the fault stayed with 1 so it must be the injector , i will get some carb cleaner and try clean it first ,if i have to buy new should i buy just one or a full set and whats recommended
Re: Help rough running car
Posted: Mon Aug 25, 2025 9:18 pm
by Speedtouch
Perhaps try removing it, leaving it connected to the loom with some fuel feed and place it to spray into a jar with the engine running, to check the spray pattern (should be an even conical shape).
I would stick to standard injectors unless the engine's heavily modified.
Re: Help rough running car
Posted: Tue Aug 26, 2025 8:41 am
by flybynite
I had problems with the injectors on my M54 after it was standing a while. Eventually they came round but not until a good few taps with the thick end of a screwdriver to free them up. Standing, bad fuel and ethanol in 95 do injectors no favours.
Not lost on me that the M20 started on the key and ran well after standing same amount of time.
Re: Help rough running car
Posted: Tue Aug 26, 2025 2:16 pm
by Corasdad
Do i take the fuel rail off to tap them is it worth spraying carb clean into it
Re: Help rough running car
Posted: Tue Aug 26, 2025 2:53 pm
by Speedtouch
No, you can try just tapping them in situ from above - do this before attempting to remove any. With a bit of luck, it will unseize itself and once the fuel starts flowing, it should clean itself.
Re: Help rough running car
Posted: Tue Aug 26, 2025 3:06 pm
by flybynite
As Speedtouch said, I just got a bit frustrated after swapping things around, I got it running on 5 (after starting on 2) but the last one wouldn't free. I gave the top of the rail over the injector a good 'tap' with what I had in my hand at the time (luckily it was a softish handled screwdriver) and it sprang to life.
Worth a try

Re: Help rough running car
Posted: Tue Mar 03, 2026 3:38 pm
by Corasdad
Right my troubles have returned same issues bad running trys stalling when reved and back firing onto intake i have done a smoke test today and had a leak qhich is fixed but still running shite,i am just waiting for fuel pressure tester recommend by dan but does anybody else have an suggestions before i give ip and sell it
Re: Help rough running car
Posted: Wed Mar 04, 2026 9:44 pm
by Corasdad
Can anybody confirm vemo are who make bmw crankshaft and camshaft sensors for e39 2.8.
New fuel pump and filter and regulator no difference
Re: Help rough running car
Posted: Thu Mar 05, 2026 11:25 pm
by Speedtouch
Have you tried doing a compression test to ensure you're getting good even figures across all cylinders?
Re: Help rough running car
Posted: Fri Mar 06, 2026 6:59 pm
by Corasdad
No not yet, i dont think its compression but worth a try ,my fuel presser tester came today so thats saturdays job
Re: Help rough running car
Posted: Sat Mar 07, 2026 11:08 pm
by Speedtouch
How did you get on with that?
Re: Help rough running car
Posted: Sun Mar 08, 2026 5:37 pm
by Corasdad
I ordered wrong one but new one has turned up today but after taking things off and putting them back on it works now no idea why, going to teat fuel pressure monday anyway
Re: Help rough running car
Posted: Mon Mar 09, 2026 3:19 pm
by Corasdad
So my fuel pressure is about 3.2bar when running,today i took off my disa ,my throttle bodyand icv all seems ok so i put it all back together and now it work again ,i have not taken her for a drive yet but this is defo a head scratcher and the trouble is i jave lost all faith in her as i have no idea what caused this and if it will come back
Re: Help rough running car
Posted: Wed Mar 11, 2026 11:07 pm
by Speedtouch
Oh well, sounds like you've at least made progress with it. I would be inclined to take it for an "Italian tune-up" to blast the cobwebs out!
Re: Help rough running car
Posted: Thu Mar 12, 2026 9:06 am
by Corasdad
Lol its on the cards but need to get wheel alignment first