Starting idle issue and one sputter with no code !!!

[saneesh8]

My Z started showing a weird issue. When starting in the morning (garage), the idle dips little (2-3 seconds) and sputter exact once and then all are fine. In the evening it wont sputter, but random idle for short time (2-3 seconds). It started showing this issues only when it started cooling down (outside temperature). Mornings are in lower 50s now.

Checked with DIS and found only code for fine fuel leak (loose fuel cap). Coolant sensor value, intake temperature value, engine oil temperature, VANOS values, all are in proper range. Other than the fine fuel leak error, all modules are fine. Battery voltage, DIS was showing 11.8 before start and 13.8 while engine idling. Once it starts, i can stop and then start with no issue. Also no issues while running even at full throttle. Checked DISA and it is working fine. Reset all adaptation done and tomorrow morning i will know if that is causing it. Also did tried all the modules like secondary air pump etc from DIS and all are working fine.

Checked the intake part and all looks fine. Belts are fine too. No weird noises or anything like that.

Most of the cooling system parts are relatively new including the coolant temperature sensor. Also the CVV is relatively new and vanos seals are also done at the same time along with the VCG. Spark plug is also new and fuel injector was cleaned and have new seals along with new fuel filter and air filter. Car still getting 21.5mpg in city driving which didn't change. Using premium fuel from Costco.

Is this normal to bmw?

Thanks..

[danomite]

You might be having cold start issues. What octane fuel are you putting in it? If you're running 93 or 91, try using 89 or 87 to see if that cures the hiccup. Don't worry, even 87 octane fuel is perfectly fine for your car (and probably even better) if your engine is normally aspirated. Plus, you'll get to save money!

[saneesh8]

I am using 91 octane from Costco. Always felt that the middle grade is better. But Costco have only regular and premium. Need to try Chevron / Texaco next time.

With 87, i can hear the knocking sound occasionally on acceleration. So i stayed away from regular.

[danomite]

I am using 91 octane from Costco. Always felt that the middle grade is better. But Costco have only regular and premium. Need to try Chevron / Texaco next time.

With 87, i can hear the knocking sound occasionally on acceleration. So i stayed away from regular.

Ahh...try the 89 then. Or try running a slightly colder plug set.

[saneesh8]

Thanks. Will try the 89 first and then see how it goes.

Today morning was ok. No sputtering. Only difference was yesterday evening, i drove it hard and then cleared the adaptation values.

[Vintage42]

You might be having cold start issues... If you're running 93 or 91, try using 89 or 87 to see if that cures the hiccup. Don't worry, even 87 octane fuel is perfectly fine for your car (and probably even better) if your engine is normally aspirated...

I don't see how octane relates to "cold start issues". And page 28 of his Owners Manual says to use 87 octane only "as an exception". That is because the engine's knock sensor will reduce advance on 87 which reduces power and mileage below the engine's ratings. From the Manual...

In order to achieve rated values for engine
performance and fuel consumption:
> Super lead-free premium gasoline
(91 AKI).
The minimum fuel quality is:
> Regular lead-free gasoline (87 AKI)
> Because of the engine's design, you
should refuel with this gasoline only
as an exception.

[danomite]

I don't see how octane relates to "cold start issues". And page 28 of his Owners Manual says to use 87 octane only "as an exception". That is because the engine's knock sensor will reduce advance on 87 which reduces power and mileage below the engine's ratings. From the Manual...

Rather than go into the dynamics of how a petrol-powered internal combustion engine works, I'll let you Google how octane determines the timing of combustion for a given motor spec. There's a lot a thermodynamics involved, not to mention fuel atomization, etc. You'll find tons of information on it, and this is pretty common knowledge amongst the (automotive) mechanically inclined. Suffice it to say, the lower the octane, the earlier/easier the combustion happens at a given temperature, per a specific compression ratio, for a given spec motor. So, 87 or 89 actually help the naturally aspirated motors in our cars during cold starts by completing the burn earlier, and thus more completely.

Feel free to research compression ratios as they apply to fuel types and fuel consistencies, too. You'll be amazed at how many variables of fuel type affect combustion for a given spec compression ratio. But I digress....

I'm just trying to help the OP with what sounds like a slight cold start issue. A simple way to help diagnose, is to try a step lower octane rating.

Cheers

[thomas88162]

You aren't getting a CEL because misfires aren't detected on a cold start. I do not know this, but I suspect they aren't detected until the car reaches closed loop operation.

[danomite]

Thanks. Will try the 89 first and then see how it goes.

Today morning was ok. No sputtering. Only difference was yesterday evening, i drove it hard and then cleared the adaptation values.

One more thing for your check list should be the Idle Control Valve (ICV). If your DISA valve shows no sign of wear, and your not getting any CEL's (specifically from the MAF sensor), then I'd suggest taking out the ICV and cleaning it thoroughly. They will get gunked up and cause idle and stuttering problems. You can search here in BFC or Google for the how-to's.

Hope this helps.

[saneesh8]

DISA valve is relatively new (like <2 yrs) and i checked it and is working fine. Oxygen sensors were also replaced immediately after this (pre-cat)

About one year ago, i had to replace the leaking water pipes and so had to take out the intake manifold. Changed all vacuum lines, CVV stuff, gaskets (including fuel injector gaskets), Coolant sensor (it was easy with the intake manifold out of the car). At that time, i cleaned the throttle body and ICV along with the intake manifold. Car developed a throttle body related errors after 6 months of this fix and had to take out the throttle body and found that i didn't locked the electrical connector and it was loose. So anyway since it was out, i cleaned the throttle body and ICV again and it was clean at that time. Also all the intake parts and other hoses, clamps etc are in good shape. I will check it again. It is almost time to fill up the gas. This time, i will try 89 from Chevron and see how it goes. Yesterday evening also it was fine. I really hope it is the gas. Fuel filter is also relatively new.

DIS still shows no errors on scanning.

I will update the details after trying out the 89 octane.

Don't know if it is related or not, i had a timing chain (secondary one which is on the top) kind of noise and i can feel the chain on left top of engine (while facing the engine) with my hand. First i changed the primary tensioner coil spring. It helped somewhat. Then i realized it is the secondary chain and it is a hydraulic tensioner. I was using bosch oil filter. Some where i read that issues with this filter and checked the filter which had <2K on it. It was almost disintegrating. Wonder if any particles went inside and was causing issues with the hydraulic tensioner. Anyway i changed it to the OEM filter and within few days, the noise was completely gone. Wonder if this issue is somewhat related to that. It never made noise after this(its been few months now). I used the cheap fram filter before and never had this kind of issue.

[328 Power 04]

Have you rebuilt your VANOS with new seals and bearings (ex: www.beisansystems.com), just a recommendation if you still have noise in the head near the vanos.

[Mr Bingley]

Have you rebuilt your VANOS with new seals and bearings (ex: www.beisansystems.com), just a recommendation if you still have noise in the head near the vanos.

This--I rebuilt my VANOS this spring and it cured my cold idle issue among a host of other evils. Mine (S52) was behaving exactly as you describe.

[328 Power 04]

...noise in the head ...

Lol. Shameless self-quote.

They have meds for the above...

[saneesh8]

I did rebuild vanos with the seals from besian systems (not the rattle fix, but just the seals).

[Vintage42]

... the lower the octane, the earlier/easier the combustion happens at a given temperature...

I think that refers to the temperature inside the running combustion chamber, not to the temperature of the outside air.

[danomite]

I think that refers to the temperature inside the running combustion chamber, not to the temperature of the outside air.

I'm not sure if you're asking me, or trying to refute what I typed. In any case, I'll try to help you:

1. Go here:http://en.wikipedia.org/wiki/Cold_start_(automotive)
2. Read all of it.
3. Pay particular attention to the part titled "Causes of Cold Starts".
4. REALLY pay particular attention to the first and third bullet-points of that section (there are only 3 bullet-points, so it should be easy).
5. Think it through, compare it to what has been posted above.
6. Embrace the enlightenment.

Lower octane fuel ignites earlier/easier (see: more volatile) at a given compression ratio, compared to higher octane fuel. When the engine (and consequently the temperature inside the recently active combustion chamber) is cold, the AFR (air-fuel ratio) is affected negatively, causing the atomized fuel to be less volatile...less "ignitable". The earlier/easier ignition (see: higher volatility) of the low octane fuel helps this.

In the OP, he states specifically that these are cold start situations...not sure if you missed that.

Here's some more light reading for you:

http://en.wikipedia.org/wiki/Reid_vapor_pressure

http://en.wikipedia.org/wiki/True_vapor_pressure

http://en.wikipedia.org/wiki/Vapor_pressure

http://en.wikipedia.org/wiki/Gasoline#Volatility

Cheers

[rf900rkw]

LMAO!!!!


All I'm going to say is that Wiki article appears to be a copy-paste from a text book written over a century ago.

[thomas88162]

I could see how lower octane fuel could help at cold start, but I have never had an issue with 93 octane. Even in very cold winter temperatures.

[rf900rkw]

Volatility (ease of vaporization) and octane (resistance to compression ignition) are not related.

[ZGator]

I HAD the cold start issue, a few times recently - exactly the same conditions as OP, I have fresh vanos update with Besian seals, and replaced my ICV not much before that.

I also had no codes.

I was running 93 for weeks, switched to 89, problem went away, so I am a believer.

(someone else here had posted this as a tip a few weeks back)

[rf900rkw]

It's not the octane change that made the difference. The volatility of the fuel must match the climate and altitude. Summer gas vs winter gas. High altitude vs low. Summer gas is harder to start on cold mornings. Winter gas can vaporlock (more a carb problem) and creates more evaporative emissions during warmer temps. There's something over 20 different summer blends for the US depending on area. We're in the transition of one to the other.

[Vintage42]

I think that refers to the temperature inside the running combustion chamber, not to the temperature of the outside air.

Volatility (ease of vaporization) and octane (resistance to compression ignition) are not related.

That is my understanding. For easier cold weather starting in northern states, refineries use an additive that increases the volatility. Neither the gas companies nor the car companies suggest using lower octane for cold weather starting. If a car has a problem getting running in cold weather, the reason is not likely the gas octane.

[saneesh8]

Since the weather improved over the last few days, it is not happening now. Will update once it cools down again.

[RayBallen]

Almost the same as mine. But mine is M44 1.9. I have intermittent sputters which disappear as the car heats up or rough on cold starts (especially if haven't driven for days) but all good on warm weather. I replaced the fuel cap seal and it improved a little bit but it's still there. I'm guessing it's a vent solenoid or purge valve. Anyone else experiencing this?