Any N42/N46 Experts Out There?

[Vass 1042]

Went 50-50 with a mate on this spontaneous project car a few months ago and so far have been struggling to pinpoint what the hell it is that's wrong with it.

And just to save everyone the trouble of pointing it out - the engine is what's wrong with it. I know. It's an absolute dog of a 4-banger. Hoping to narrow it down a bit from there.

Wouldn't have touched it otherwise but what it's got going for it is that it's got 3 pedals from factory, so that brings the score up a bit.

We've (seemingly) tried everything to get her running and are pretty much at our wit's end so hoping the wider hive mind might have some helpful ideas to try and save this ugly duckling.

BACKSTORY

She's a rather gutless little 316ti with the dreaded N42B18 engine and 165,330km on the clock.

All we know is around 3 years ago it developed a "rough idle" and was parked up. A local rally shop owner bought it from one of his clients with the intentions of dropping an M54 in it and turning it into a rally car but never got around to it. After 3 years of sitting it now wouldn't fire up at all so having lost interest he decided to get rid after some quick attempts to get her running didn't lead to anything.

I was alerted to it by @Eagle, recognised the name of the fella selling it, quickly got in touch and snapped it up.

One other historical tidbit is that in 2018 at 160,700km it got brand new timing chains, guides, tensioners and a bunch of associated seals & gaskets, from Christchurch BMW no less, so it's got one of the 3 big ticket items taken care of at least.

WHAT WE'VE DONE

Started off by giving the car a good wash, chucked in a battery and read the codes.

Checked out the VVT motor only to find the lead not even plugged it. In addition some of the sheeting on the wires was damaged that got fixed with some electrical tape.

Plugged back in, cleared the codes, the car will crank and crank but won't start. Checked the fuses, checked fuel pump relay all seemed good. No sound from the fuel pump with the ignition on so sounded like it wasn't priming but seems like these cars operate in some weird, different way, more on that later. Left it there and came back another weekend.

Hooked up the battery, tried to start it more out of blind hope than anything and to our massive surprise it fired right up after a few cranks. Even held idle nice and steadily. What a weird little thing. Drove it from the paddock into the garage and onto the hoist. It drove fine but it was stuck in limp mode, still due to the VVT (valvetronic motor) and wouldn't rev above 2.5k RPM.

Up on the hoist we unhooked some fuel lines, drained the remainder of the old fuel from the tank and put some 10-15L of fresh 95 in there. Dropped her back down only for her to refuse to start up again... Cranked away for ages but no dice.

Removed the valve cover, checked & cleaned the eccentric shaft sensor, swapped in a spare valvetronic motor from a newer 120i, hooked it all up, ran the stop limit adaptation procedure with a scan tool - all ran fine indicating the valvetronic motor and eccentric shaft sensors were both operational. Buttoned it all up, still crank no start. Good thing is no VVT-related codes have come back since, suggesting the fault being to do with a faulty old valvetronic motor. Only code remaining in the DME is for the ambient temperature sensor, which is inconsequential.

Decided to check compression and found ~50 PSI across all cylinders which made no sense since the car was running earlier that day. Having read about it potentially being due to the cylinders being flooded with fuel from all the cranking, getting washed down and not sealing properly, assumed it was that and left it there.

Came back to it a few weeks later and checked compression again before trying to fire up and risking flooding the cylinders again. Found 170-200 PSI this time around, which was more like it.

Also checked fuel pressure. Not sure how these cars operate but with ignition on fuel pressure remained at 0. Only after starting cranking it spiked to 45 PSI then dropped down to 40, and kept falling gradually. After a whole heap of cranking we managed to get her running again just the once. Fuel pressure remained steady at 45 PSI at idle, then dropped with the engine turned off and went all the way down below 20 PSI just 20-something minutes later, indicating potential leaky injectors. So we got the fuel rail out to check.

VIDEO

Weirdly enough, with the injectors unhooked the car actually fired up for a few seconds and sounded pretty good doing it, much to my mate's audible surprise. The spray pattern seemed roughly consistent and we couldn't note any leakage afterwards with the ignition off either.

Spark plugs were completely soaked and reeked of fuel so we swapped in a spare set. Also swapped out some coils for newer spares, checking spark prior to dropping them in. Crank no start.

Decided to try another weird experiment by dropping the sparks & coils half way down into the cylinders, which did look quite cool.

VIDEO

Not sure what this actually tells us apart from maybe that the firing sequence looks weirdly random and inconsistent? The Pattern should be 1342 but it looked like it it skipped one or two cylinders nearly every round. Maybe that's just because it's not all sealed perfectly tight, other than that no idea why it would be off.

Bolted everything back on but still...

Got fuel, got spark, got compression.

Crank no start.

 

Our informed approach has since descended into a crude exercise of 'throwing sh*t at the wall and seeing what sticks' with nothing seemingly sticking. We've since swapped out to a good second hand fuel pump, swapped out fuel filter & regulator, swapped out injectors, swapped out the crank sensor... Haven't been able to get the car running again at all ever since the trick with the injectors. And it got some fresh oil somewhere along the way as well.

LIST OF POTENTIALS

• Take apart & clean out ignition switch
• Check DME connections for oil contamination
• Check fuses in DME box, swap out DME relay
• Update DME software?
• Borrow timing tool & check timing (probably should have been the first thing to do, although would it have run at all if it were off?)

 

But yeah, that's where we're at. Sorry for the long waffle but thought I'd best lay it all out there.

Good thing is that if we were to turn around and part the poor thing out we'd still easily break even so we haven't crossed into silly-territory just yet. As frustrating as it's been at least all we've got to lose is our own time. At this point we're trying to get her running more out of curiosity rather than some pressing desperation but we're quickly running out of ideas.

She's a nice wee car and would be a shame to strip it for parts. The compacts aren't the prettiest things out there but I do quite like the look of it in full Msport trim, especially after seeing how well @Harper's one turned out. Was hoping to get her up and running to compare and potentially swap it out with my Swift Sport as a daily driver since it's still a much nicer and more familiar place to be rather than the Suzuki.

Other idea was to swap in an M54 but at that point it becomes another weird project car that neither me nor my mate need, nor is there any market for if we were to build to sell. As fun as it would be with a 6-pot it'd be a dumb idea for a daily driver since it'd never get anywhere close to the 7L/100km I get in the Swift, and I already have my "fun" M54 car.

Anyway, any thoughts, ideas, words of wisdom much appreciated

[Olaf 3405]

how're you getting on with this?  I know you've had Barbara to keep on developing, and your Tractor too...

[Vass 1042]

32 minutes ago, Olaf said:

how're you getting on with this?  I know you've had Barbara to keep on developing, and your Tractor too...

The past few months have been real hectic, we've been too busy developing a new human for me to spend any real time in the garage so haven't made enough progress to warrant an update. Should finally have a bit of time this weekend though so will see if I manage to get anywhere with it.

Coincidentally, yesterday marked 1 year since we bought it but it's no closer to being back on the road. The co-owner mate had lost interest in it and being parked up in another mate's paddock on the opposite end of town I've just had too much going on to take on an hour long round trip every time I wanted to work on it. So about a month ago the mate loaded it onto a trailer and dropped it into my driveway so now I can slowly tinker away at it whenever I have a bit of time.

All I've done so far is disconnect the DME and inspect it. What I found was some oil on the main engine harness plug that had migrated along the wiring from one of the sensors/solenoids all the way to the DME, which is apparently a thing that happens... In our case it's just a tiny amount that I could see but the car hasn't run in a good 4 years now so it might have had more there and it's just dried out over time.

In any case, I sprayed both ends down with contact cleaner spray, then took the DME out of its casing to inspect for any other damage that might stand out but all looked fine to my unscrupulous eye.

That's about as far as I've gotten with it so far, am yet to reinstall the DME back into the car to see if that did anything. I want to again remove the intake manifold and give everything a going over before attempting another start, will then check/clean the ignition switch and try resync the DME to the EWS and eliminate that as a possible culprit.

This car would make a nice base for an M54 swap but with a barely 3-month old daughter keeping us on our toes and being down to one income I won't have the time nor the finances to turn it into a proper project any time soon. So my hopes are to get this thing running well enough that I can daily drive it for a few years, then see how I feel about it further down the line. If I don't manage to bring it back to life soon then I'll unfortunately be forced to put it out of its misery.

[Olaf 3405]

Aye, those first couple or five or more years are a tough time - no spare finances - though ultimately rewarding.  The Ti will find its way - maybe the BMW universe will smile on you benevelently for your work keeping others alive!  Our kids have become adult flatmates - not something we intended - and they still amaze me.

Even M54B25 these things go very well - look for thread by @TIM325i (The Incredible Machine) he took a standard 316Ti or 318Ti and worked out all the parts to retrofit and make it a 325Ti Msport, it was very well-sorted and went very nicely.

Edited May 8 by Olaf
TIM325

[Vass 1042]

Time for a long overdue update on this little piggy. Here's a summary of all my efforts over the past month or so.

All our previous attempts had led us to believe the issue to be electrical and having found oil on the DME plugs I went further down that rabbit hole. I removed the intake manifold, revealing the junction box for the engine loom. I opened it up to discover a couple of plugs drenched in oil so figured I might as well remove the whole thing and give it a good clean.

I traced the drenched plugs to the cam sensor wiring at the front of the engine. I also removed the cam sensors themselves to check them out. They were the older design ones with a thinner end bit becoming wider half way along with a rubber seal at the junction. That rubber seal had all but perished on one of the sensors and along with external leaks, seemed to also shooting oil straight through into the plug.

I swapped in some spare, newer design cam sensors I had handy, as well as the crank sensor for good measure. I then went through the whole loom with contact cleaner spray, tidied up the whole thing and reinstalled it.

I then moved inside, removed the ignition switch and gave that a good clean. Those are known to cause all sorts of erratic electrical issues and was good to eliminate as a possible culprit. One of the connection spots was really gummed up with carbon dust so could have been beginning to be problematic.

I then checked all the fuses, both in the glovebox and whichever ones I could find in the DME box. All checked out fine. With the battery fully charged, I gave starting it a go.

Crank, no start.

The only DME code showing up was for the ambient temperature sensor, the one on the passenger side fender liner, which had of course gotten ripped out at some point in its life. I always thought that it's only there for the cluster display and the operation of the HVAC system so not sure why it was showing up as a DME code. Nevertheless, I spliced in a spare sensor and plug to get rid of the fault code at the very least. Code now gone, it still made no difference.

It was only at that point that I decided to do the thing I should have done as the first step. I borrowed a timing tool kit from a fella I'd bought some parts from a while ago, opened up the valve cover and had a fresh peek inside. The intake cam locking tool was a real tight squeeze to install but finally went in, only to then move over to the exhaust side and find it nowhere near fitting.

Bastard.

[Vass 1042]

That was a massive oversight on our part. Should have checked timing as the first thing but I guess since we managed to get the car running and idling perfectly smoothly a couple of times we just assumed that the timing wouldn't have been the issue. It must only have been marginally out, not beyond what the valvetronic system could compensate for, but not consistently enough for some reason.

How, when and why it skipped timing is a bit of a mystery. The car has 165,331km's on the clock. At 160,736km's it had a timing chain, guide, tensioner etc replacement done at Christchurch BMW so it hadn't even done 5k km's since then. Weird one all around.

When picking up a spare valvetronic motor a year ago, it came with a whole valvetronic assembly that I parked up on a shelf but now came in quite handy. I figured since I'm disturbing timing anyway, I might as well remove the whole thing, give it a checkover and a clean. I started on the spare unit as a test run before removing the one from the car and tearing that one apart as well. The video series from BimmerZen was super useful throughout the whole process.

Straight away it became apparent that the unit that came off the car was in real shoddy state. Whether from neglect during its life or purely from sitting for close to 6 years now the surfaces on the tappet arms (or whatever you call them) and eccentric shaft had become quite badly pitted and looked really rough.

Luckily, I had the second unit on hand and between the two of them made up one decent one.

All put back together, the car would now start every time but would run rough and want to die soon after. A few tries later, assisting with the throttle, it began running a bit more consistently but accompanied with loud pops which sounded like backfiring into the intake manifold. I then looked in the rear view mirror only to see a big while cloud from having smoked up the whole street. I then remembered that the fuel would have been sitting in the tank for near enough a year and probably wasn't in ideal state.

Decided to drain it and replaced it with 10L of fresh BP98, just to give it the best chance at life. After a few more tries, probably helped by the fact of built up oil pressure, it would now run without stalling, but still erratically backfiring into the intake manifold. I was even brave enough to take it for a lap around the block, clocking up a whopping 1.2km whilst sputtering lightly.

VIDEO

That's the state of things for the time being. Showing signs of life but not quite back to full health. The backfiring could be something as simple as a vacuum leak, or a more serious undiagnosed issue that took it off the road in the first place. Either way, needs more effort (and money) thrown at it. Just not sure how far to take it. Would hate to jump in head first and start throwing money at it only to take it for a WoF and find out something fundamentally wrong that would make it wildly uneconomical to remedy. Ideally, I'd figure out a way to get it running smoothly enough for it to make its way to the inspection, get a full list of issues and reassess from there. More tinkering for another weekend.