Start the engine twice?

[TheEinstein]

I have to ask if anyone else has a theory here. When I start the engine, it has a bit of a rough idle, and fuel economy can suffera little bit. It'll act like it's over fueled and won't have the power I think it should have. This engine is a Nikasil, and it's 1 year since fully rebuilt. Every sensor is checked, rather new, and there are no codes.

To get around this at the moment, I start the engine, let it run for a few seconds, shut it down (turn key to position 1), and restart. At that point it runs tip-top. Occasionally it'll do just fine on the first start, but I'd hesitate to say more than 20% of the time at best.

Any theories or experience is welcome.

[ross1]

I have(wife's car really) an E39 that infrequently does the same. Runs poorly, misses, on start up but if shut down and immediately restarted is fine.
My theory is a fuel injector(s) leaking down and flooding a cylinder(s). If the DME detects a certain # of misfires I believe it shuts down fueling, to preserve the cats. This would explain it clearing after a re-start.
Engine management is different for your car and mine but I wonder if the same fuel shut down with misfiring is present in the E34 DME.
All this reminds me I have set of fresh injectors on the shelf for it.
I'm curious to hear of any others experiencing this and about any solutions.
RE a "fully rebuilt" nikasil engine. Really?
Fuel wash is disastrous for these engines BTW

[TheEinstein]

That is a plausible explanation. I haven't tried another set since rebuilding, but I can look into it.

FWIW, I did take them apart and do the flush, back flush, ultrasonic bath, flush and backflush, screen replacement treatment. I even once had another set I did the same to and subsequently sold when I felt confident they were not my culprit. In any case, maybe I can check static fuel pressure before start. Of it's staying up, that would rule them out right..?

Regarding the engine, yep. New rings, bearings, honed cylinders, lapped valves, completely decarbonized, valve springs matched, all new seals, really everything under the hood that was rubber or a sensor, is new. Including the power steering lines. Oh what a relief it is to have zero leaks! Compression and leakdown tests show to be solid still after about 10k miles.

[ross1]

I'm curious about the honing, supposedly not possible to get a correct finish

[Mykk]

I don't believe the Motronic M3.3 is intelligent enough to shut cylinders down on misfire. Has the stomp test produced ant trouble codes?

[TheEinstein]

Nope, no codes. I've had an out of range o2 trigger, but I'm pretty sure it's a tiny leak around the injectors. Honestly not in months now though. And my only suspicion there was because when I was snapping the elec box cover down, pressing on it, I heard the vacuum leak while pressing. I can reproduce this still, and intend on resealing, but it hasn't seemed as relevant. Maybe it is, but I couldn't tie it to the restart and fix scenario.

As for the hone, I spoke to BRM and was pointed at the:


GB314240AO (83mm 240-Grit Aluminum Oxide Flex-Hone)

It worked really great. Barely used it, just wanted a finish that oil would stick to, and that's exactly what I got. There was zero texture change by touch noted, just barely cross-hatched. My main concerns expressed to them were the thin Nikasil wall coatings, obviously, and the need to not enlarge the cylinders as I was using factory rings and keeping the pistons.

[XAlt]

M60s flood a lot, drive longer.

Honing Alusil can be done at home, but Nikasil is a coating on an all aluminum block... You coat it or you use a liner.

[TheEinstein]

I definitely accepted the facts when I moved forward with my rebuild. I recognize it could always be it's last trip, and that my direction was I'll advised at best, but I was already too far to turn back and wasn't in a position to buy another engine. It is what it is, and I'll have an oil analysys performed on my next oil change.

As for trips, it's ran a half-hour from work to home (12 miles between 25mph and 60mph) then not until the morning. So it's not short trip syndrome.

Thanks for the thought though.

[TheEinstein]

If mods stop by please remove this post. Thx

[Mykk]

I agree with XAlt, the m60's do fuel flood easily. Usually revolves around the coolant temp sensor.

[ross1]

M60s flood a lot, drive longer.

Honing Alusil can be done at home, but Nikasil is a coating on an all aluminum block... You coat it or you use a liner.

https://www.bimmerforums.com/forum/s...Nikasil-blocks
Here is some info I dug up a while back;

[XAlt]

https://www.bimmerforums.com/forum/s...Nikasil-blocks
Here is some info I dug up a while back;

http://m.renn-list.com/DIY-Alusil-cy...0632490-2.html

[TheEinstein]

For what it's worth, I did a huge amount of research on the subject of even touching those cylinder walls. I called numerous coveted engine builders, and spoke to probably a dozen in total. Majority said, move on sir, and a few said they had positive and lasting results if handled with care. I am very aware of the actual process and the scale of roughness, or Ra, involved. Hence the "proper," if you will, tooling noted. Every time I start her up, I know it could grenade. Regardless, it's what I've got, and I'll be back to share it's catastrophic failure (knocks on wood) when (hopefully if) that day comes. I moreover did it for the science, and because I was told it couldn't be done.

Coming back to the subject, I think I should be more accurate in my description of how it runs. When I say rough, what I mean is not as smooth. When I rebuilt it, I even took the time to round the piston rod edges, and balance all eight of them to within half a gram. I believe TIS said within like 3 grams was acceptable. I bought a digital valve spring tester, and since I had a spare set of heads, matched 32 spring sets to within 0.3 lbs. None were off more than 1lb anyhow IIRC, but I was going for gold and wanted a smooth run. Point is, when it is running optimally, I could stand a coin up on it running.

So when I say rough, I mean two or three bonded coins might not stand up, not rough like door shaking when open. Sorry if I was misleading. It's most notable when accelerating. Akin to the difference between launching in Drive, vs launching in "4" or "Sport." Though not exactly that drastic. Which is why I do resonate with a fueling issue, but also want to pojnt at the ECU or TCM too. Both of which I have at least four of. I've had them all in prior to the teardown and rebuild, but maybe I need to dig them back out, and have a go at some swaps. In the meantime, I'll order anothe ECTS for sh!#s and giggles. I can move the pedal through a large range and have no extra acceleration. I just usually back off the gas on a minor incline to watch my MPG gauge get better until I notice it no longer holding accel up the hill.

If any other ideas come up, please don't hesitate to share though. I really appreciate the input my friends.

[nonturbodan]

By starting the engine twice you're loading it up with a good amount of extra fuel. It does not know that it has already run once when you start it the second time so it is applying full cold start enrichment.

These things often run a little better on the rich side. I found the best idle quality to be in the mid 13:1 AFR range in the case of my old turbo e28. The factory is trying to minimize emissions and fuel consumption so what you get is a tune that is the best overall compromise of driveability and power within the confines of what can be done with a catalytic converter and closed loop fuel control.

[TheEinstein]

By starting the engine twice you're loading it up with a good amount of extra fuel. It does not know that it has already run once when you start it the second time so it is applying full cold start enrichment.

These things often run a little better on the rich side. I found the best idle quality to be in the mid 13:1 AFR range in the case of my old turbo e28. The factory is trying to minimize emissions and fuel consumption so what you get is a tune that is the best overall compromise of driveability and power within the confines of what can be done with a catalytic converter and closed loop fuel control.

So what are you suggesting? Everything is still completely stock, and I'm not following the message it seems. Are you saying it may be the ECTS as well? Sorry, for my confusion.

[nonturbodan]

It may be an air leak. May be nothing at all. The stock tune is leaner than ideal and the engine will not run as smooth as it does with a little more fuel. That's why its smoother if you start it twice. It loads up a little more on fuel.

[TheEinstein]

Ok, well I'll put a thorough smoke test on my list too. Out of curiosity, is this something others have gotten around using a performance chip? I've been looking for a solid excuse to make that leap, but I've held off because availability and consensus on which one and type (ECU vs TCM) are all over the place.

[ross1]

Seeing your subsequent posts I'm convinced your issue is nothing like mine described earlier. Yours seems a minor thing while mine was a hard miss.
Adding a performance chip to an undiagnosed "problem" doesn't seem like a good idea from here. I'd have a properly running engine first.

[TheEinstein]

Seeing your subsequent posts I'm convinced your issue is nothing like mine described earlier. Yours seems a minor thing while mine was a hard miss.
Adding a performance chip to an undiagnosed "problem" doesn't seem like a good idea from here. I'd have a properly running engine first.

I agree with you, but I couldn't help wondering if there was something remotely feasible about how a chip might have effected the fuel map.

Well, I've ordered an ECTS, and will finish making my smoke machine to eliminate the usual crap for sure.