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View Full Version : Rough idle when cold, no other symptoms


luciano136
05-09-2005, 01:16 PM
I have been reading a lot about the 'rough idle' issue. I saw there was a previous post but that was also combined with the engine light that came on.

On my 99 2.8, I do experience a little bit of rough idle when the engine is cold. It would sometimes rev down to 500 and then back up. When the engine is warm, perfectly smooth and no other warning lights or driving problems.

I also had a recent oil change but that did not affect the 'problem'. Is this something to be worried about? Or should I just ignore it? I have 46k miles now...

Thanks!

pjhansman
05-09-2005, 02:08 PM
Up here in the cold country, I usually solve that problem with a bit of "gas line antifreeze" to get rid of the water that builds up in the tank from condensation.

Somehow I'm guessing that isn't as big a problem in the sunny south

Ron Stygar
05-09-2005, 02:20 PM
I have been reading a lot about the 'rough idle' issue. I saw there was a previous post but that was also combined with the engine light that came on.

On my 99 2.8, I do experience a little bit of rough idle when the engine is cold. It would sometimes rev down to 500 and then back up. When the engine is warm, perfectly smooth and no other warning lights or driving problems.

I also had a recent oil change but that did not affect the 'problem'. Is this something to be worried about? Or should I just ignore it? I have 46k miles now...

Thanks!
All my cold start, rough idle problems went away when I switched to Shell V-Power.

luciano136
05-09-2005, 03:22 PM
Well, I will definitely try that. I use the premium gas from chevron now and I think it's even a little bit more expensive than the v-power. I might as well switch then! Great engines but definitely picky huh ;-).

TurnAround
05-09-2005, 04:41 PM
little bit of rough idle
My '02 Coupe started having rough idle / start problems. I thought it was the cold at first. Thanks to these boards I learned.. it was the battery.

If she sits for even a week, the problem will start to crop up. Drive her a lot... problem goes away (no matter how cold it is). The more people I ask, the more I hear the story... infrequent driving is really hard on the battery. Don't know how often you drive your Z, but I thought I'd mention it.

I bought a new Interstate battery last week. Putting it in tonight. I emailed with Interstate today. They said a fully charged battery shows a voltage of 12.7%. A 75% charge (25% drop in battery power) will measure out to be 12.45 volts. Below 75% and the battery will go through sulfation, the plates will begin a cycle of damage... and it all goes down hill from there.

So you see.. it doesn't take much of a drop in voltage for a battery to start having problems. After I put this new one in I'll check the voltage every few days. If sitting for a week to 10 days unused / driven causes even a 10% drop, i'm getting a battery tender.

Might not be an issue for you. The info may help someone tho. :)

BMcCoupe
05-09-2005, 10:51 PM
My '02 Coupe started having rough idle / start problems. I thought it was the cold at first. Thanks to these boards I learned.. it was the battery.

If she sits for even a week, the problem will start to crop up. Drive her a lot... problem goes away (no matter how cold it is). The more people I ask, the more I hear the story... infrequent driving is really hard on the battery. Don't know how often you drive your Z, but I thought I'd mention it.

I bought a new Interstate battery last week. Putting it in tonight. I emailed with Interstate today. They said a fully charged battery shows a voltage of 12.7%. A 75% charge (25% drop in battery power) will measure out to be 12.45 volts. Below 75% and the battery will go through sulfation, the plates will begin a cycle of damage... and it all goes down hill from there.

So you see.. it doesn't take much of a drop in voltage for a battery to start having problems. After I put this new one in I'll check the voltage every few days. If sitting for a week to 10 days unused / driven causes even a 10% drop, i'm getting a battery tender.

Might not be an issue for you. The info may help someone tho. :)

That is interesting... i don't drive my coupe that often, and I park outside, so the BMW car charger thing isn't a solution for me either.

Starfury
05-10-2005, 10:12 AM
I have a E46 (99) 328i SE and i have been getting bad idling problems but only when the engine is warming up.
I start her up in the morning she sits on 1000rpm I pull off down to the bottom of the street and drive for about 1/2 - 2/3 of a mile and stop at the roundabouts traffic lights then she sits on 900rpm, drops to 800 to 700 in steps down to 300 - 500rpm and then recovers back upto 900rpm. Seems to be a slight hesitations when accelerating hard like mini flat spots till it hits the power band.
Once she has warmed up to normal everything is fine.

I have read about 6 different reasons for bad idling from sticking air idle valves to VANOS control units needing replacing to an engine remap...

Does anyone have a definitive answer or is it a trial an error game?
Also if left is it likely to cause damage or hefty repair bills as I am about to send it into the garage next week as its still under warranty.

Starfury

Starfury
05-17-2005, 02:07 AM
Last week I started using Shell Optimax petrol and the problem seems to be lessening.
The really interesting bit is it doesnt seem to be affected by engine temp as the gauge has been on normal and its still done it for about 5 minute after starting the engine.
So what else could cause it....?

edit:
But only happens if the engine has been left off for a few hours

rjcoston
05-17-2005, 08:58 AM
As pjhansman suggested below, you could try a gas additive that absorbs moisture from your fuel system. An even cheaper substitute is 91% rubbing alcohol.

luciano136
02-20-2006, 11:28 AM
Well, after a couple of months the rough idle came back! Last time after an oil change and changing to Shell V-power, things seemed to be smooth again.

Granted I am 5000 miles into my last oil change but that shouldn't be a problem. Can new spark plugs make a difference in this issue? I'm going to replace them soon and I'm pretty sure it's never been done (1999 with 55k miles).

Thx again for all the feedback!

caylan
02-20-2006, 01:47 PM
I have a E46 (99) 328i SE and i have been getting bad idling problems but only when the engine is warming up.
I start her up in the morning she sits on 1000rpm I pull off down to the bottom of the street and drive for about 1/2 - 2/3 of a mile and stop at the roundabouts traffic lights then she sits on 900rpm, drops to 800 to 700 in steps down to 300 - 500rpm and then recovers back upto 900rpm. Seems to be a slight hesitations when accelerating hard like mini flat spots till it hits the power band.
Once she has warmed up to normal everything is fine.

I have read about 6 different reasons for bad idling from sticking air idle valves to VANOS control units needing replacing to an engine remap...

Does anyone have a definitive answer or is it a trial an error game?
Also if left is it likely to cause damage or hefty repair bills as I am about to send it into the garage next week as its still under warranty.

Starfury

My problem was a bad Mass Airflow Sensor.
Idle high & then dies.
Have to restart car.

madhouse
02-20-2006, 05:38 PM
I have a E46 (99) 328i SE and i have been getting bad idling problems but only when the engine is warming up.
I start her up in the morning she sits on 1000rpm I pull off down to the bottom of the street and drive for about 1/2 - 2/3 of a mile and stop at the roundabouts traffic lights then she sits on 900rpm, drops to 800 to 700 in steps down to 300 - 500rpm and then recovers back upto 900rpm. Seems to be a slight hesitations when accelerating hard like mini flat spots till it hits the power band.
Once she has warmed up to normal everything is fine.

I have read about 6 different reasons for bad idling from sticking air idle valves to VANOS control units needing replacing to an engine remap...

Does anyone have a definitive answer or is it a trial an error game?
Also if left is it likely to cause damage or hefty repair bills as I am about to send it into the garage next week as its still under warranty.

Starfury

My problem was a bad Mass Airflow Sensor.
Idle high & then dies.
Have to restart car.
caylan


2000 Z3 2.8 does the same thing. Did you have any error codes for the Mass Airflow Sensor? I have no codes showing.

caylan
02-20-2006, 06:15 PM
2000 Z3 2.8 does the same thing. Did you have any error codes for the Mass Airflow Sensor? I have no codes showing.


Sorry, I took it to the dealer on the last day of my CPO warranty & that's what they said.
Never crossed my mind to ask for error code.
In retrospect, that would have helped us all out.

There is a chance that it's on my bill...I'll check later when I go home.

afrad
02-21-2006, 04:42 PM
I have a similar problem with my 2000 328Ci with 60k miles. It seems to only happen on cold mornings when the temp is 40ish or below. Car idles very rough like there is a miss and occasionally gets worse to the point of the Service light coming on. The "miss" goes away with increased rpm's and once the engine temp rises. I've not noticed an effect on driving other than if I am at a red light before the engine warms up and the service light comes on, then I need to pull off and restart the car (once the engine light comes on there is a noticable loss in power and what seems like a misfire.) Once the car is restarted the service light goes off but unless the engine has warmed up in the interim, the rough idle persists. I have had it to the dealer twice (actually 3 times, picking it up after the second service it did it in their parking lot.) Here's what they have done:
1) Replaced the pulse generator and spark plugs. Also got an oil change at this time. I use the synthetic oil. The problem persisted.
2) Replaced a single ingnition coil. The problem persisted.
3) The foreman then drove the car for 2 days and did a fuel system treatment. The problem seemed to decrease for a day or two (the weather was also a little warmer) but now the rough idle is back full force.

I don't know what to do at this point, but I am tired of paying the dealer to take guesses. Their latest theory is that the lifters need to be replaced (~$2000!!)

I might try to replace all of the ignition coils with aftermarket coils from bavauto.com.

Any other suggestions? I feel like my description of the problem is too good for the dealership to not know what it is and I am frustrated. The car is otherwise great and when the engine is warmed up drives fantastic.

afrad
02-21-2006, 04:52 PM
I just found this thread for anybody interested.

http://forum.e46fanatics.com/showthread.php?t=145540&highlight=cold+rough+idle

firedwg1
02-21-2006, 06:02 PM
Check your MAF sensor!!! It may need to be replaced Good luck

caylan
02-21-2006, 08:08 PM
...

I don't know what to do at this point, but I am tired of paying the dealer to take guesses. Their latest theory is that the lifters need to be replaced (~$2000!!)

...

Any other suggestions? I feel like my description of the problem is too good for the dealership to not know what it is and I am frustrated. The car is otherwise great and when the engine is warmed up drives fantastic.

MAF Sensor for the 3rd time.

luciano136
02-22-2006, 10:47 AM
Thx for all the replies! I changed the spark plugs last night and didn't notice any rough idle this morning. If it does show up again, I'll keep the MAF sensor in mind.

Is it hard to replace? Any idea on cost of the part?

firedwg1
02-22-2006, 01:11 PM
Get the car scanned for codes first...

MAF
http://www.vacmotorsports.com/cgi-bin/special_view.pl?man=BMW

location: between the air filter and air intake

I hope this answers your questions

fobguy
03-28-2006, 08:26 PM
That goes for me too (Mass Air FLow Sensor) 400 bux.........

ATLBMW
06-25-2006, 10:39 AM
All my cold start, rough idle problems went away when I switched to Shell V-Power.

Funny you should say that .... the dealer I got my car from had it filled on shell vpower car ran perfect but when i switched to Chevron gas I got a slight rough idle on warm up issue... hmmmm...