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Problems after cleaning Throttle Body
Thread Starter
Junior Member
Joined: Aug 2011
Posts: 19
Likes: 0
From: Gulfport, MS
c240
Problems after cleaning Throttle Body
I am having a few issues after cleaning my throttle body. To start off I have a 2002 C240 with 175,000 miles. The other day I decided to clean out my throttle body, because of a rough and low idle. I removed the MAF, the elbow, and the hoses connecting to it. I cleaned it out the throttle body, lifted back the butterfly to get behind and around the edges of it... I tried to do the best I could with the room I had. Upon removing the hoses, I broke the driver side breather hose because of how dry rotted it was. It idled at about 2,000rpm and my gas mileage was terrible. After making a trip to the dealer to replace the hose $16.05, and putting it on there I started my car, and seemed well. Well, after going around the neighborhood, and coming to a stop I experience a rough downshift. I bring it back to the house and the car is idling high still. Not exactly 2,000rpms, but I would say around 1,200 to 1,400rpm. The two odd things is that I sometimes come back to a stop and put it into neutral and it is idling normally. The other weird thing is that the throttle seems very sensitive by just tapping it very slightly. I don't have anything to read any codes, but I don't have any kind of CEL. The only thing I could think is that I maybe messed up the throttle body servo..?
Senior Member
Joined: Aug 2013
Posts: 283
Likes: 2
From: Toronto, ON
2012 C300 Sport 4MATIC (current) 2006 C280 Elegance 4MATIC (sold)
Make sure you placed the airbox firmly down and the air filters inside it are properly seated in. That can definitely cause a high idle. It might be something more but try that first.
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Joined: Jan 2005
Posts: 2,848
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From: Orange County
2005 C Wagon (No snickering please!)
Thread Starter
Junior Member
Joined: Aug 2011
Posts: 19
Likes: 0
From: Gulfport, MS
c240
I have triple checked that everything from the elbow up is firmly in place. Could it be some kind of rubber gasket/ o-ring?
Thread Starter
Junior Member
Joined: Aug 2011
Posts: 19
Likes: 0
From: Gulfport, MS
c240
Thread Starter
Junior Member
Joined: Aug 2011
Posts: 19
Likes: 0
From: Gulfport, MS
c240
I would like to thank everyone for their help. This is my first Mercedes, and they seem to be pretty overly engineered.. Which is not what I am use to.. Coming from a 93 240sx
Junior Member
Joined: Sep 2013
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mercedes cl500
Check all the vacuum lines all the breathing hoses make sure they are nice an tight. The smallest leak can cause the most annoying fluctuation when u come to a stop. Also I forget what the sensor is called but there is one tht bolts to the intake manifold it has a screen on it if u pull it off the manifold u should see it. Its rigg by where the tb bolts up but sometimes they get gunk on them. I'm new with mercedes myself but I'm learning somewhat quickly.
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Super Moderator
Joined: Mar 2007
Posts: 5,295
Likes: 22
From: VA
THE C350
So you cleaned the TB with it still on the car? I would finish the job and take it off of the car clean it fully and replace the gasket that goes between it and the Intake. As everyone has said also check for loose vacuum hoses and wires you may have damaged. This will also give you the opertunity to look at the TB better and if you want to clean out the motor side (some one posted pictures on here which would be helpful) I would also check the MAF and get some MAF cleaner if it is the original one/ very old. Also make sure the MAF is plugged in and that the air cleaner seal and the plastic tube seals are good. I changed mine a year or so ago and they were rock hard and fell apart into three or four pieces while a new one is like a rubber band. Then make sure that you don't have any air leaks bypassing the MAF or air cleaner.
As you said this car is over engineered but honestly not very different than any other car built in the last 10 years... your Nissan was just outdated and simple (I miss my older cars they were so simple
.)
As you said this car is over engineered but honestly not very different than any other car built in the last 10 years... your Nissan was just outdated and simple (I miss my older cars they were so simple
.)
Last edited by samaritrey; Nov 27, 2013 at 01:07 PM.
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Senior Member
Joined: Aug 2013
Posts: 283
Likes: 2
From: Toronto, ON
2012 C300 Sport 4MATIC (current) 2006 C280 Elegance 4MATIC (sold)
I hear you about the Nissan bit. I had a 2000 Maxima before buying my C280 and it was darn easy to work on and had arguably the best V6 motor of all time in it. The thing is it felt like a tin can compared to the Benz which feels very solid. These MB cars aren't all that daunting although a delicate touch is required in some aspects when working on it. I'm wondering if you may have damaged your MAF since you said the issues go away when the car warms up. I know when the MAF sensors on the Maximas went bad people complained of a hesitation when the car was cold but the problems were non existent when it warmed up. What did you clean your MAF with?
Junior Member
Joined: Jul 2011
Posts: 57
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2006 C230 & 2002 C230
He didn't..... according to his first post.
But I think he should have cleaned the MAF since it was already out and who knows if got contaminated while it was out.
1. Clean the MAF (take it out & clean).
2. Reclean the TB again. Possibly ISC (idle speed control) assy got clogged or contaminated.
3. Once all assembled, while engine is idling, spray carb cleaner around the air intake joints. If idle rises, you have an intake leak.
Below photo is from my C230 MAF cleaning.
But I think he should have cleaned the MAF since it was already out and who knows if got contaminated while it was out.
1. Clean the MAF (take it out & clean).
2. Reclean the TB again. Possibly ISC (idle speed control) assy got clogged or contaminated.
3. Once all assembled, while engine is idling, spray carb cleaner around the air intake joints. If idle rises, you have an intake leak.
Below photo is from my C230 MAF cleaning.
Thread Starter
Junior Member
Joined: Aug 2011
Posts: 19
Likes: 0
From: Gulfport, MS
c240
He didn't..... according to his first post.
But I think he should have cleaned the MAF since it was already out and who knows if got contaminated while it was out.
1. Clean the MAF (take it out & clean).
2. Reclean the TB again. Possibly ISC (idle speed control) assy got clogged or contaminated.
3. Once all assembled, while engine is idling, spray carb cleaner around the air intake joints. If idle rises, you have an intake leak.
Below photo is from my C230 MAF cleaning.
But I think he should have cleaned the MAF since it was already out and who knows if got contaminated while it was out.
1. Clean the MAF (take it out & clean).
2. Reclean the TB again. Possibly ISC (idle speed control) assy got clogged or contaminated.
3. Once all assembled, while engine is idling, spray carb cleaner around the air intake joints. If idle rises, you have an intake leak.
Below photo is from my C230 MAF cleaning.
Senior Member
Joined: Aug 2013
Posts: 283
Likes: 2
From: Toronto, ON
2012 C300 Sport 4MATIC (current) 2006 C280 Elegance 4MATIC (sold)
Yeah these cars do need to maintained a bit more often with more replacements compared to a Japanese car but do it little by little if it isn't urgent. This year I took care of the filters (engine and cabin), engine oil and filter, spark plugs, MAF and TB cleaning and fuel filter by myself and the dealership that I bought it from replaced the oil cooler due to a leak before I bought it. Next year I'll take it to a indy who will drain, flush, replace filter and refill the transmission for me (messy job) and I'll also have the front and rear differential oil replaced whiles it at the shop up on the hoist.
