Limp mode/lagging engine

[gemmer22]

Hi guys. Im stumped im currently driving a 2009 120i E87 BMW, she has recently been giving me one same problem, a lagging engine the best i can explain is slow acceleration, aggressive vibration in the engine bay, almost no power and cuts off at times. Also struggling to start.

I've now replaced the Injectors,ignition coils,spark plugs,intake manifold with gaskets, MAF sensor, throttle body and the battery with all OEM parts, ive also cleaned both Vanos and Cam sensors with Carb cleaner, however after thousands of Rands she is still doing exactly the same things i honestly don't know what can be wrong anymore ?
The errors we get on INPA are manufacturers error and misfire on cylinder 1 and 2 but it goes away on it's own and comes back again. As well as the check engine light.


Ps there is a hissing noise in the engine bay when starting her, I've checked there are no leaks in and around the manifold.

Please help, im just a girl who wants to drive her BMW properly again.

 

[Greenz]

Have you had a compression and/or cylinder leakage test done?

 

[gemmer22]

Have you had a compression and/or cylinder leakage test done?

Not yet, would you be so kind as to explain how this could be a cause to the symptoms?

 

[Swiegie1]

Hi

A compression test is fairly cheap.

Check the, I think, two vacuum lines that runs on top of the engine. If they are perished it will cause vacuum leaks and maybe also the hissing sound.

I assume this is the N46 engine.

Also check the PCV valve.

Hope this helps.

 

[Teezoh]

The best question to ask is what area you're in? Have a reputable shop look at it for you rather than trying to diagnose it yourself. It might save you more than trying to go through your own checklist.

As @Greenz said, low compression can be caused due to warn valve seals or piston rings.
Camshaft/Crankshaft sensors can also cause it if faulty
Simple wiring problem can also cause it

 

[gemmer22]

Update we've done a compression test and there is proper pressure (my brother already did this i was unaware 😅) , the one mechanic we have in Potchefstroom takes our car for a few days tells us it's one thing we fix it and the it's another, the last time she was there he said he was gonna send her to a Bosch service centre (which was ridiculously overpriced for them to also not know whats happening, their Launch machine also said misfire on cylinder 1&2 ) so we are currently back to square one. 🫡

 

[gemmer22]

Hi

A compression test is fairly cheap.

Check the, I think, two vacuum lines that runs on top of the engine. If they are perished it will cause vacuum leaks and maybe also the hissing sound.

I assume this is the N46 engine.

Also check the PCV valve.

Hope this helps.

Yep N46 engine, the PCV valve had in my opinion (i might be just uneducated) a lot of oil build up. Im not sure if it is possible to clean it up a bit and if that might help diagnose if that might be the issue.

 

[M3boi]

A compression test will only tell you so much, ideally you should do a compression test and a leakdown test thereafter.

 

[gemmer22]

Update for all, we disabled the VVT. She is driving perfectly and has not had any issues since Saturday, fingers crossed that this is the light at the end of the tunnel.