Engine works unstably only in Idle speed ?

[se4y]

The engine of My 2008 e85 z4 works unstably only in idle speed of D or R. It was going well in other situation. The speed will drop only a second and become normal again.(I have changed spark plug and fuel filter already but it did not work) Has someone met the same situation and can give me some advice?Thank s a lot!!

[Caddyshk]

Throttle position sensor

[BruceJ]

Could be a leaky vacuum hose or cracked up CCV system. Had similar symptoms at idle (along with going though a bit more oil than usual and Cel's pointing towards O2 sensors, bad coils & worn rings) in my 03 330i.

Turned out to be just the CCV. Not alot of fun to replace but immediate difference.

[se4y]

Originally Posted by BruceJ

Could be a leaky vacuum hose or cracked up CCV system. Had similar symptoms at idle (along with going though a bit more oil than usual and Cel's pointing towards O2 sensors, bad coils & worn rings) in my 03 330i.

Turned out to be just the CCV. Not alot of fun to replace but immediate difference.

Thank you very much for read my thread and your advice. I looked up dictionary and can not find "cel"means what . Does CCV means closed crankcase ventilation ?Would you pls give me more information(z4 e85 2008 ) Should I change o2 sensor first? thanks a lot for your time and help

[JeffchaPz]

Hello amigos,

for the past year or so, I noticed that when cruising between 3k RPMs down to 2.5K RPMs back to 3K X3 = the SES light shows up.

The car keeps running normal. It clears it self after 6 or 8 cycles but as soon as I start cruising in those #s.... that freaken light comes on.
Once in a while the RPMs will drop at idle and the car will shake a little > but once I start going.... the car drives fine.

Every time I check for codes I get the ones on the picture below. I just order a $220 O2 sensor and I hope that solves the problem.

I guess I should check the CCV? How do you check the Throttle Position Sensor and what should I look for?

OP > didn't mean to take over, but it sounds like we have the same problem


Cheers !!!

[BruceJ]

Originally Posted by se4y

Thank you very much for read my thread and your advice. I looked up dictionary and can not find "cel"means what . Does CCV means closed crankcase ventilation ?Would you pls give me more information(z4 e85 2008 ) Should I change o2 sensor first? thanks a lot for your time and help

Yes, CCV means Closed crankcase ventilation. If you have a 3.0 engine http://www.realoem.com/bmw/showparts.do?model=BU33&mospid=49304&btnr=11_3738& hg=11&fg=15

O2 sensor is last thing I would test/replace
I would check:
1. Air Intake filter dirty?
2. Disconnect/ reconnect MAF sensor looking for change in idle. If idle gets worse when disconnected then MAF probably okay
3. Is the rubber intake boot intact, no cracks?
4. Test each coil - while engine is running disconnect/reconnect each one individually. No idle change while disconnected means coil possibly bad.
5. Are there any vacuum leaks, broken/disconnected vacuum hoses?
6. Is the CCV system intact? Cold weather and time will cause cracks. if so this causes a lack of vacuum that can cause poor idle, excessive oil burn, fouled plugs, etc
Good luck
Bruce

[BruceJ]

Originally Posted by JeffchaPz

Hello amigos,

for the past year or so, I noticed that when cruising between 3k RPMs down to 2.5K RPMs back to 3K X3 = the SES light shows up.

The car keeps running normal. It clears it self after 6 or 8 cycles but as soon as I start cruising in those #s.... that freaken light comes on.
Once in a while the RPMs will drop at idle and the car will shake a little > but once I start going.... the car drives fine.

Every time I check for codes I get the ones on the picture below. I just order a $220 O2 sensor and I hope that solves the problem.

I guess I should check the CCV? How do you check the Throttle Position Sensor and what should I look for?

OP > didn't mean to take over, but it sounds like we have the same problem
Cheers !!!

You probably have two different engines - se4y didn't mention having a Z4"M". If you, I would check all the same things I mention to him, cause they are cheap and easy to check/replace. But intermittent SES at speed makes me think vanos/cam sensor. Also, have you have the valve lash tested/adjusted. Try looking at the M3 forums for similar problems.
Good Luck
Bruce

[JeffchaPz]

Originally Posted by BruceJ

You probably have two different engines - se4y didn't mention having a Z4"M". If you, I would check all the same things I mention to him, cause they are cheap and easy to check/replace. But intermittent SES at speed makes me think vanos/cam sensor. Also, have you have the valve lash tested/adjusted. Try looking at the M3 forums for similar problems.
Good Luck
Bruce

Thanks Bruce... you threw me off by your /// M bumper.

I had this problem before and after my valves/shims were checked. For now, Let's hope the new O2 fixes what the car is telling is wrong... if not, then I have a feeling that is vanos related.

Thank you much sir!

[StickMon]

Originally Posted by se4y

... I looked up dictionary and can not find "cel"means what. ...

cel = Check Engine Light
also called
ses = Service Engine Soon

2C93 is Exhaust Gas Temp Sensor Plausibility.
2FDA is Crank Case Ventilation, System Check.

Inspect your wiring to make sure nothing got fried by the headers and take off the head-cover cover and make sure no wires are pinched.

[se4y]

:c

Originally Posted by StickMon

cel = Check Engine Light
also called
ses = Service Engine Soon

2C93 is Exhaust Gas Temp Sensor Plausibility.
2FDA is Crank Case Ventilation, System Check.

Inspect your wiring to make sure nothing got fried by the headers and take off the head-cover cover and make sure no wires are pinched.

thansa！I will try.Thank you!

[se4y]

My Z4 : e85 2.5si N52 engine.It seems no CCV system? Is it inside the engine?

[se4y]

Originally Posted by BruceJ

Yes, CCV means Closed crankcase ventilation. If you have a 3.0 engine http://www.realoem.com/bmw/showparts.do?model=BU33&mospid=49304&btnr=11_3738& hg=11&fg=15

O2 sensor is last thing I would test/replace
I would check:
1. Air Intake filter dirty?
2. Disconnect/ reconnect MAF sensor looking for change in idle. If idle gets worse when disconnected then MAF probably okay
3. Is the rubber intake boot intact, no cracks?
4. Test each coil - while engine is running disconnect/reconnect each one individually. No idle change while disconnected means coil possibly bad.
5. Are there any vacuum leaks, broken/disconnected vacuum hoses?
6. Is the CCV system intact? Cold weather and time will cause cracks. if so this causes a lack of vacuum that can cause poor idle, excessive oil burn, fouled plugs, etc
Good luck
Bruce

so kind of you! I will study and inspect onebyone.thanks！

[se4y]

Originally Posted by se4y

The engine of My 2008 e85 z4 works unstably only in idle speed of D or R. It was going well in other situation. The speed will drop only a second and become normal again.(I have changed spark plug and fuel filter already but it did not work) Has someone met the same situation and can give me some advice?Thank s a lot!!

I check for codes by the dealer but no bad information there.

[BruceJ]

Originally Posted by se4y

My Z4 : e85 2.5si N52 engine.It seems no CCV system? Is it inside the engine?

Take a look at item 14 in the link - I think it will end up being underneath your intake manifold.
http://www.realoem.com/bmw/showparts...37&hg=11&fg=15

Good Luck