Timing? Or stalling?

[Primitivesmith]

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Hi all! First ever post though I've been stalking the halls for a while for a lot of great help on this troublesome engine

Basically, I came into a 2.0 z4, e85, and have had my work cut out due to it starting to stall, and then not rev above 2500. I've systemically, using inpa, cleared all engine related codes, by changing the usual : eccentric shaft sensor, vanos solenoids, valvetronic motor, and reinstalled all with a new rocker cover gasket.

However, even though there are no longer any codes to read on ista, it's now no longer firing up at all. Starter cranks fine, but never takes. A bit frustrating, but I thought maybe there was a air leak as the new gasket was pretty stiff, so taking it off today, I thought I'd check timing once more before adding sealant to the mix to help pin cover down. However, Ive noticed that the timing is out! Could this be a symptom of the variable timing when trying to start up, or is this something else? I wanted to get cover on and fire up later today after applying the sealant with cover but now sht scared there's a timing issue that's starting to surface, but I wasn't sure if the vvt kicks in on startup. Any help would be greatly appreciated, super confused right now as to whether to stick the cover on and fire it up or dig deeper into it

If it helps, the timing was fine when the valvetronic motor wasn't working at all. So something has changed!

[tug]

Welcome to the forum mate, your problem is definitely vvt related, with it almost stalling & not reaching over 2500 that is a failed vvt. You mention having replaced the valvetronic, did you prime it before starting the engine?

Also, is it a used vvt or new? if used then it is probably not working also.

Hope you get it sorted mate.

Cheers, tug

[Primitivesmith]

Hi tug! Apologies for the delayed reply, I didn't get any notifications and works been a little busy so just picked back up with the car again. I really appreciate the help as it's an absolute conundrum to me

Indeed the vvt was new, and was primed through ista plus using the procedure, which completed just fine, and I had a buddy there to cop a feel of the motor and make sure that it was indeed turning.

A couple of updates to some more fixes I've tried :
4 new Injectors, same problem no change
The engine will just about start now if I remove the vanos solenoids.. It will seem to idle indefinetly, but then under load again at about 2000 or 2500 revs in neutral it just shakes the sht out of the engine and then will fall back to stalling level, sometimes catch itself and sometimes not. But plugging in the vanos solenoids it almost makes it teeter out to stall.

To be fair it had these problems when I got it, and drove horrendously. It's just so unusual to me that after fixing (at least the sensors are happy) these problems that it would persist.

It made me think of fuel/air/spark, bu after the new Injectors have made 0 difference, now I'm second guessing myself again

Not to sound daft as the vanos thing is new to me, but should it not at least run with all vvt stuff unplugged? I mean if it's not going above 2500 and all vvt is disabled, to my mind I think throttle body (seemed fine on removal, no reported problems on ista) Injectors (changed as a precaution but to no avail) or exhaust. Has anyone ever heard of a collapsing cat in these that threw no codes etc?

Many thanks for any replies, I've done a fair amount of spannering in the past but never found a car to uneager to work when it's got everything it needs on inspection to drive. I have also trawled the forums for a very long time for any sign of something I might be missing, but nothing quite like this comes up

[tug]

Mate, when you inspected the throttle body, how did the paddle feel? You should feel quite a resistance when pushing it. Also, was it clean, could there be any carbon build up preventing its operation? You're symptoms could be pointing towards this.

Also try unplugging the maf and see how it performs, could be a failed unit.

It would be a good idea also while you have Ista plugged in, to delete the VVT adaptations.

Hope you get it sorted.

Cheers, tug