rough idling

SZMB · 06-22-2009, 01:09 PM

1998 C280 132k mi. The idling is smooth when in P or N and RPM is ~800, but rough idling in D and RPM drops to ~600. Has anyone experienced this problem? Could the problem related to the ICV? Any input is appreciated.

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tex07 · 06-22-2009, 03:01 PM

mass airflow sensor? could be a problem with sensing air/fuel ratio is my guess.

SZMB · 06-22-2009, 05:27 PM

Good suggestion. I disconnected the MAF sensor, and the idling is very smooth through all the gears. I'll try to clean it with a can of carburetor cleaner first, and if that doesn't fix the problem, i'll get a new sensor. Have you ever tried to clean the MAF sensor first before buying a new sensor? Thanks for the help.

rfoo · 06-26-2009, 02:10 AM

I think cleaning the sensor is possible but you really have to take precaution as it is really sensitive. I read an article here or club202 about how to clean them with care. try researching it.

SZMB · 06-26-2009, 01:05 PM

I cleaned the sensor w/ a whole can of MAF cleaner. The idling is a little better, at least the car does shake anymore, but it's still too rough for my liking. I'll go ahead and order the sensor online. The dealer wants $350. The online store autohausaz.com is $185. Not sure if it's OEM part.

ob1kenobi · 06-26-2009, 03:25 PM

I agree with cleaning the MAF sensor.

Did you get any cel code? What is it?

SZMB · 06-26-2009, 05:01 PM

No fault codes. I just purchased the MAF sensor online, hopefully that will fix the problem.

$tallion · 06-27-2009, 04:14 PM

I think its CRC cleaner. Spray it SPray it again if that dont fix it then I dont know what to tell you..you might need a new maf...I Had the same issue this fixed mine

SZMB · 07-03-2009, 03:06 AM

I just got a new MAF installed and the idling has improved in Drive gear. However, there's still this low frequency humming sound from the engine, and RPM at 600, and still not as quiet as in P or N. But after driving for about 10 mins and the car is warmed up, idling is very smooth in any gear. Has anyone experienced this problem, i.e. idling becomes very smooth after the car is warmed up?

egreckis · 07-19-2009, 06:48 PM

I have the rough idle at 600 rpm until it warms up and the runs smooth after that. Where is the MAF located??

rfoo · 07-20-2009, 06:21 AM

Located after the airbox and before the cross intake pipe. It's a round thing with a plug connected on top.

egreckis · 07-21-2009, 10:20 PM

Thanks I found the MAF as well as the Overvoltage Protection Relay Module. From what I can visually see the MAF seems clean. So I am not sure if it is bad.. The relay I think is my main problem so I will see if I can acquire thru a mechanic I know. Thanks for the all the help..

bagelsjustbagel · 07-22-2009, 04:03 AM

i have the exact same thing. the car kinda rumbles but rpms stay around 600?

New motor mounts will probably fix that

rfoo · 07-22-2009, 10:15 AM

I had a similar problem which I thought got fix when I cleaned my spark plug and connecting wires. It went away after awhile but came back just recently. Changed the motor mounts thinking it was the problem but didn't help.

Mine shakes at idle mildly...

But then again it's a case to case basis. It might work for you but not mine. I suspected my MAF so I'll probably clean it and see what happens.

wesrick · 07-23-2009, 12:12 PM

So, can someone explain how to 'clean' the MAF?

Pics are OK!

egreckis · 07-24-2009, 01:00 AM

I found the overvoltage module at a local MB repair shop and it did the trick. Runs normal now. The guy said when I asked him for the part "yep pretty common to hear that they go out." Now it runs smooth again. It cost $65.00.

ll1l2l1l2lll · 07-25-2009, 11:20 AM

this recently happened to me. however it only rumbles at idle. when i put on the gas, it just stops and runs normallly (however sometimes without a lot of power) happened driving on the freeway with a lot of traffic. motor got pretty hot. mine rumbles like crazy though.

egreckis · 07-25-2009, 10:58 PM

Okay.. Turns out the overvoltage module was not the problem. The MAF was the problem. Got a hold of one in local parts shop. Cost $210.00. Ran the car for about 100 mi. and had no issues whatsoever. So that must have the whole problem..

g3llings · 08-02-2009, 12:38 PM

I'm hoping a new MAF will solve my problem. My car runs so rough right now that as soon as I switch to drive it almost stalls... and if I hit the accelerator it gets even worse. Makes sense to me... If I am already running lean and open the throttle body to let in more air without the MAF recognizing it im going to stall or very close to it.

g3llings · 08-04-2009, 06:46 PM

update:

I had the coil pack which controls cylinders 1 and 6 replaced. My car will actually run now, but the rpm's still drop to around 600rpm when I shift into reverse or drive, and I still have a slight misfire... I disconnected the MAF sensor and the car seems to run a little better, but not perfect... does this mean the MAF is the problem, or could it also be the overvoltage relay or Throttle Position Sensor since removing the MAF doesn't totally solve the problem? Seems like it could still run a little rough since the computer then has no read at all of the air flow, right?

egreckis · 08-16-2009, 04:36 PM

ad the coil pack which controls cylinders 1 and 6 replaced. My car will actually run now, but the rpm's still drop to around 600rpm when I shift into reverse or drive, and I still have a slight misfire... I disconnected the MAF sensor and the car seems to run a little better, but not perfect... does this mean the MAF is the problem, or could it also be the overvoltage relay or Throttle Position Sensor since removing the MAF doesn't totally solve the problem? Seems like it could still run a little rough since the computer then has no read at all of the air flow, right?[/quote]

I had the same issue and disconnecting the MAF did the same thing. After replacing it, it ran normal. Your problem sounds like the same thing. Shop the unit as the price seems to run quite a range. I've seen on ebay for as low as $45.00 but I bought at a parts shop for $165.00. Need is a costly thing.

g3llings · 08-16-2009, 07:13 PM

Thats true. Unfortunately the dealership tells me that the problem is the wiring harness, but maybe I'll get lucky and a new MAF will fix it? The dealers are always trying to get the most money possible. Thanks

wesrick · 08-23-2009, 01:35 AM

I found the MAF cleaner at my local parts store - used about half a can on it, but still rougher than a skunk.

I know I need to replace at least one of the O2 sensors - could that be causing a rough idle?

egreckis · 09-05-2009, 02:20 PM

Got a check engine light. Buddy loaned me his OBD to see what code would come up. It was P0505 idle control system malfunction. Seems pretty common but the repair not that easy. Need to check several items for correct settings or replace. So I am going to attempt to test any suggestions?

egreckis · 10-17-2009, 02:28 PM

I have replaced both the MAF and the overvoltage modules... I still got a check engine code P090505 turns out that could include vacuum leaks.. So I followed a couple of the vacuum lines and indeed found one brittle one I replaced. The idle than kicked up to 750 rpms, but is not consistent so I will be looking to replace as many plastic vacuum lines as it takes to see if my problem is solved.. My car ran about like yours when I disconnected the MAF so you may be experiencing the same anomaly as I am..

06-26-2009, 02:10 AM	#4
rfoo Member Join Date: May 2008 Location: Manila, Philippines Posts: 248 Drives: 1994 C220	I think cleaning the sensor is possible but you really have to take precaution as it is really sensitive. I read an article here or club202 about how to clean them with care. try researching it. __________________ 18" AMG Replica S600 Grill Projector Headlight McCulloch H.I.D 6000K K&N Air Intake H&R Sports Spring

06-27-2009, 04:14 PM	#8
$tallion Member Join Date: Sep 2008 Location: Clearwater, Fl Posts: 234 Drives: 1997 C280 SPORT	I think its CRC cleaner. Spray it SPray it again if that dont fix it then I dont know what to tell you..you might need a new maf...I Had the same issue this fixed mine __________________ Louis John

07-19-2009, 06:48 PM	#10
egreckis Newbie Join Date: Jul 2009 Location: Southwest Washington State Posts: 8 Drives: 1995 C280	rough idle I have the rough idle at 600 rpm until it warms up and the runs smooth after that. Where is the MAF located?? __________________ egreckis

07-20-2009, 06:21 AM	#11
rfoo Member Join Date: May 2008 Location: Manila, Philippines Posts: 248 Drives: 1994 C220	Located after the airbox and before the cross intake pipe. It's a round thing with a plug connected on top. __________________ 18" AMG Replica S600 Grill Projector Headlight McCulloch H.I.D 6000K K&N Air Intake H&R Sports Spring

07-21-2009, 10:20 PM	#12
egreckis Newbie Join Date: Jul 2009 Location: Southwest Washington State Posts: 8 Drives: 1995 C280	rough idle Thanks I found the MAF as well as the Overvoltage Protection Relay Module. From what I can visually see the MAF seems clean. So I am not sure if it is bad.. The relay I think is my main problem so I will see if I can acquire thru a mechanic I know. Thanks for the all the help.. __________________ egreckis

06-22-2009, 03:01 PM	#2
tex07 Member Join Date: Feb 2007 Posts: 125 Drives: 2000 C230 sport	mass airflow sensor? could be a problem with sensing air/fuel ratio is my guess.

06-22-2009, 05:27 PM	#3
SZMB Member Join Date: Jul 2007 Location: San Jose, CA Posts: 118 Drives: 2004 E500	Good suggestion. I disconnected the MAF sensor, and the idling is very smooth through all the gears. I'll try to clean it with a can of carburetor cleaner first, and if that doesn't fix the problem, i'll get a new sensor. Have you ever tried to clean the MAF sensor first before buying a new sensor? Thanks for the help.

06-26-2009, 01:05 PM	#5
SZMB Member Join Date: Jul 2007 Location: San Jose, CA Posts: 118 Drives: 2004 E500	I cleaned the sensor w/ a whole can of MAF cleaner. The idling is a little better, at least the car does shake anymore, but it's still too rough for my liking. I'll go ahead and order the sensor online. The dealer wants $350. The online store autohausaz.com is $185. Not sure if it's OEM part.

06-26-2009, 03:25 PM	#6
ob1kenobi Senior Member Join Date: Mar 2006 Posts: 274 Drives: moon buggy	I agree with cleaning the MAF sensor. Did you get any cel code? What is it?

06-26-2009, 05:01 PM	#7
SZMB Member Join Date: Jul 2007 Location: San Jose, CA Posts: 118 Drives: 2004 E500	No fault codes. I just purchased the MAF sensor online, hopefully that will fix the problem.

07-03-2009, 03:06 AM	#9
SZMB Member Join Date: Jul 2007 Location: San Jose, CA Posts: 118 Drives: 2004 E500	I just got a new MAF installed and the idling has improved in Drive gear. However, there's still this low frequency humming sound from the engine, and RPM at 600, and still not as quiet as in P or N. But after driving for about 10 mins and the car is warmed up, idling is very smooth in any gear. Has anyone experienced this problem, i.e. idling becomes very smooth after the car is warmed up?

07-22-2009, 04:03 AM	#13
bagelsjustbagel Senior Member Join Date: Jul 2007 Location: San Francisco Bay Posts: 369 Drives: 1997 C36 AMG	i have the exact same thing. the car kinda rumbles but rpms stay around 600? New motor mounts will probably fix that __________________

07-22-2009, 10:15 AM	#14
rfoo Member Join Date: May 2008 Location: Manila, Philippines Posts: 248 Drives: 1994 C220	I had a similar problem which I thought got fix when I cleaned my spark plug and connecting wires. It went away after awhile but came back just recently. Changed the motor mounts thinking it was the problem but didn't help. Mine shakes at idle mildly... But then again it's a case to case basis. It might work for you but not mine. I suspected my MAF so I'll probably clean it and see what happens. __________________ 18" AMG Replica S600 Grill Projector Headlight McCulloch H.I.D 6000K K&N Air Intake H&R Sports Spring

07-23-2009, 12:12 PM	#15
wesrick Newbie Join Date: Aug 2008 Posts: 15 Drives: 1998 C280	So, can someone explain how to 'clean' the MAF? Pics are OK!

07-24-2009, 01:00 AM	#16
egreckis Newbie Join Date: Jul 2009 Location: Southwest Washington State Posts: 8 Drives: 1995 C280	I found the overvoltage module at a local MB repair shop and it did the trick. Runs normal now. The guy said when I asked him for the part "yep pretty common to hear that they go out." Now it runs smooth again. It cost $65.00. __________________ egreckis

07-25-2009, 11:20 AM	#17
ll1l2l1l2lll Junior Member Join Date: Apr 2009 Location: san gabriel / costa mesa CA Posts: 60 Drives: w202	this recently happened to me. however it only rumbles at idle. when i put on the gas, it just stops and runs normallly (however sometimes without a lot of power) happened driving on the freeway with a lot of traffic. motor got pretty hot. mine rumbles like crazy though.

07-25-2009, 10:58 PM	#18
egreckis Newbie Join Date: Jul 2009 Location: Southwest Washington State Posts: 8 Drives: 1995 C280	Rough Idle Okay.. Turns out the overvoltage module was not the problem. The MAF was the problem. Got a hold of one in local parts shop. Cost $210.00. Ran the car for about 100 mi. and had no issues whatsoever. So that must have the whole problem.. __________________ egreckis

08-02-2009, 12:38 PM	#19
g3llings Newbie Join Date: Aug 2009 Posts: 15 Drives: 1995 C280	I'm hoping a new MAF will solve my problem. My car runs so rough right now that as soon as I switch to drive it almost stalls... and if I hit the accelerator it gets even worse. Makes sense to me... If I am already running lean and open the throttle body to let in more air without the MAF recognizing it im going to stall or very close to it.

08-04-2009, 06:46 PM	#20
g3llings Newbie Join Date: Aug 2009 Posts: 15 Drives: 1995 C280	update: I had the coil pack which controls cylinders 1 and 6 replaced. My car will actually run now, but the rpm's still drop to around 600rpm when I shift into reverse or drive, and I still have a slight misfire... I disconnected the MAF sensor and the car seems to run a little better, but not perfect... does this mean the MAF is the problem, or could it also be the overvoltage relay or Throttle Position Sensor since removing the MAF doesn't totally solve the problem? Seems like it could still run a little rough since the computer then has no read at all of the air flow, right?

08-16-2009, 04:36 PM	#21
egreckis Newbie Join Date: Jul 2009 Location: Southwest Washington State Posts: 8 Drives: 1995 C280	rough idling ad the coil pack which controls cylinders 1 and 6 replaced. My car will actually run now, but the rpm's still drop to around 600rpm when I shift into reverse or drive, and I still have a slight misfire... I disconnected the MAF sensor and the car seems to run a little better, but not perfect... does this mean the MAF is the problem, or could it also be the overvoltage relay or Throttle Position Sensor since removing the MAF doesn't totally solve the problem? Seems like it could still run a little rough since the computer then has no read at all of the air flow, right?[/quote] I had the same issue and disconnecting the MAF did the same thing. After replacing it, it ran normal. Your problem sounds like the same thing. Shop the unit as the price seems to run quite a range. I've seen on ebay for as low as $45.00 but I bought at a parts shop for $165.00. Need is a costly thing. __________________ egreckis

08-16-2009, 07:13 PM	#22
g3llings Newbie Join Date: Aug 2009 Posts: 15 Drives: 1995 C280	Thats true. Unfortunately the dealership tells me that the problem is the wiring harness, but maybe I'll get lucky and a new MAF will fix it? The dealers are always trying to get the most money possible. Thanks

08-23-2009, 01:35 AM	#23
wesrick Newbie Join Date: Aug 2008 Posts: 15 Drives: 1998 C280	I found the MAF cleaner at my local parts store - used about half a can on it, but still rougher than a skunk. I know I need to replace at least one of the O2 sensors - could that be causing a rough idle?

09-05-2009, 02:20 PM	#24
egreckis Newbie Join Date: Jul 2009 Location: Southwest Washington State Posts: 8 Drives: 1995 C280	rough idle Got a check engine light. Buddy loaned me his OBD to see what code would come up. It was P0505 idle control system malfunction. Seems pretty common but the repair not that easy. Need to check several items for correct settings or replace. So I am going to attempt to test any suggestions? __________________ egreckis

10-17-2009, 02:28 PM	#25
egreckis Newbie Join Date: Jul 2009 Location: Southwest Washington State Posts: 8 Drives: 1995 C280	rough idling I have replaced both the MAF and the overvoltage modules... I still got a check engine code P090505 turns out that could include vacuum leaks.. So I followed a couple of the vacuum lines and indeed found one brittle one I replaced. The idle than kicked up to 750 rpms, but is not consistent so I will be looking to replace as many plastic vacuum lines as it takes to see if my problem is solved.. My car ran about like yours when I disconnected the MAF so you may be experiencing the same anomaly as I am.. __________________ egreckis

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