mis3

Happened a few times in the past week, the car hesitated when I stepped on the gas pedal. The RPM stayed in the same level, about 600, and would not rev-ed up. Everything went back to normal after a few seconds. The car was finally warmed up at the time and I was stopped at the light. The car drives great for the rest of the time. No malfunction in the cluster.

This is the similar experience I had back in May-2008 and the MAF was replaced under warranty. However, I remember last time the RPM level did go up and down and it went so low that the engine died a few times.

Is this a symptom of a dirty or defective MAF?

Glyn M Ruck

I would clean the MAF. I would also check fuel pressure at the Schrader valve on the fuel rail that feeds all injectors - must be >55psi. Engine stumble can also be caused by O2 sensors getting tired & cycling too slowly. Please check that the air cleaner housing is down tight over the MAF.

For clarification. Is this only happening when the engine is running open loop during warm up when fuel demand is the highest? i.e It does not happen when the engine is fully warm & running closed loop.

mis3

I cannot remember how it happened the first few times, it was earlier this week.

Today when it happened, the car was fully warmed up and I was at the traffic light.

I think I noticed it on Tuesday or Wednesday but it did not happened at all on Thursday and Friday. I felt something was wrong but it recovered by itself quickly. Today's occurrence was the worst, I stepped on the gas paddle twice and it did not go. It waited for 2-3 seconds and it worked. I wondered if it would work if I floored the pedal.

Altogether it happened maybe 4 times so far. Hope it will go away by itself.

Glyn M Ruck

Hmm! Let us know how this develops. Could also be the TPS going sick. TPS = Throttle Position Sensor.

mis3

If this is a MAF issue, would a code be generated?

Last time as well (May-2008) when they replaced the MAF, there was no malfunction in the cluster.

Glyn M Ruck

The MAF seldom generates a code itself - usually only fuel trim related codes - eg. "mixture lean Bank 1.

The CEL function needs to be understood. So that one does not get lots of false alarms the system counts fault codes for a specific fault such as misfires. Only when the number of misfires reach a predetermined threshold does the OBDII system turn on the CEL or generate a display warning.

So you can be throwing codes but no have a CEL light burning.

This is why if you experience a driveability problem you should download codes. The system can be storing codes with no dash light on.

mis3

Based on my symptons, this should be fuel related, not transmission related?

I will go to the indie and read the code. If MAF issues, what code(s) should I expect? P0170, P0173???

I just calle dthe dealership. The MAF sensor costs $641 CAN. Wow !

Mka77

That's robbery. I would either try cleaning it yourself or have the indie do it first.

Then check some online parts places like this example for a new OEM unit;

http://www.autohausaz.com/search/pro...0Mass%20Sensor

mis3

Yes, I will go to the indie tomorrow to get the code (if any).

I went to the link you suggested (Autohaus) and here is what I found:

http://www.autohausaz.com/search/pro...1426373@CLK320 COUPE&year=2004&cid=22@Fuel %26 Air System&gid=5068@Air Mass Sensor

Can someone tell me the correct MB part number?

I called Autohaus and the calls failed, probbaly because the 1-800 number is not available from Canada.

Glyn M Ruck

These are engine or throttle related issues (includes fuel supply). They have nothing to do with transmission.

Let's see if she is storing any codes, clean the MAF & check the fuel pressure.

MAF related codes:

P0170 Fuel Trim Malfunction (Bank 1)
P0171 System too Lean (Bank 1)
P0172 System too Rich (Bank 1)
P0173 Fuel Trim Malfunction (Bank 2)
P0174 System too Lean (Bank 2)
P0175 System too Rich (Bank 2)

TPS related codes:

P0220 Throttle/Pedal Position Sensor/Switch B Circuit
Malfunction
P0221 Throttle/Pedal Position Sensor/Switch B Circuit Range/
Performance Problem
P0222 Throttle/Pedal Position Sensor/Switch B Circuit Low Input
P0223 Throttle/Pedal Position Sensor/Switch B Circuit High
Input
P0224 Throttle/Pedal Position Sensor/Switch B Circuit
Intermittent
P0225 Throttle/Pedal Position Sensor/Switch C Circuit
Malfunction
P0226 Throttle/Pedal Position Sensor/Switch C Circuit Range/
Performance Problem
P0227 Throttle/Pedal Position Sensor/Switch C Circuit Low Input
P0228 Throttle/Pedal Position Sensor/Switch C Circuit High
Input
P0229 Throttle/Pedal Position Sensor/Switch C Circuit
Intermittent

mis3

I found a Canadian site, about the same price.
http://www.autopartsway.ca/PartDetai.../pagenum1/tabS

Does anyone here have experience with Autopartsway?

I called them and while they said this was an OEM part (as indicated in their site), they did not know the MB part number. The only part number they have was BOS1600866. I am concerned because of the price difference; $641 from the dealership and $180 here.

Mka77

Dealer prices are overinflated beyond human comprehension.

The parts I have ordered throughout the years from different online sources have always been spot on, and direct replacement fitment at a huge savings.

Don't always have to get all hung up with MB part numbers.

mis3

With the MB part number, I can be sure that I am getting the right part. MB probably has differnet MAFs for different models.

http://www.autohausaz.com is good this way, they usually list the corresponding MB part number.

Glyn: Thanks for the codes. I will go to the indie tomorrow to check if it throws a code. Where is the TPS (any pictures)?

Glyn M Ruck

Accelerator assembly. These days you have to buy the whole assembly.

https://mbworld.org/forums/attachmen...ccelerator.pdf

BenzClk320

CLK 320 2003 Need technical assistance please! Was driving on highway (had driven roughly 100 miles) pulled off to exit and as soon as I parked the car, it fluttered and lost power. Only the battery light came on and off quickly. Waited a couple of minutes and was able to restart the car and drive about a 100 yards before it fluttered again and lost power completely. No lights came on this time. Had it towed to dealership. They can't figure out what the problem is. Now that car has cooled, it drives fine.

Similar issue happened 2 years ago and dealership couldn't diagnose problem. Another repair shop replaced the Crank Sensor and car ran fine for 2 years and then this happened again. Dealer thinks it's the EIS...but that doesn't make sense! There is no problem turning the car on and off. Had them check the alternator, crank sensor, and battery. All is ok according to them.

Don't want to spend $1000 in repair unless sure what the problem is. Anyone have any knowledge of this or similar experience? Thinking about taking is somewhere else for further assessment.

Glyn M Ruck

Next time it does this pour water over the CPS to cool it. They get hellish hot where they are mounted. Your CPS might well be failing again.

Pray it's not the EIS - expensive job!

mis3

Went to my indie earlier and he hooked up the computer. He did not find any fault code related to my problem.
He did see some "stored" fault codes that he cleared them. There was one fault code related to a temp sensor that he cleared as well. He said he would check if this code reappear next time.

He said my issue was probably not MAF related. If MAF related, my RPM would fluctuate. I recall when it happened on Saturday, I was stopped at the light, I stepped on the gas pedal and it would not rev while the RPM stayed stable (at around 500 RPM).

Not sure if this is fuel related. If bad fuel, I would experience lost of power. On my way home before, I went up to 100 mph with no issue.

Glyn M Ruck

I don't agree with your Indy that the RPM would fluctuate. Sometimes MAF problems only show themselves when demand is placed on the engine but stumble can be caused by many things. I would still clean the MAF.

I guess it's a relief that there are no codes but let's just watch the problem. TPS seems the most likely cause. i.e. You put your foot on the gas but the throttle plate in the throttle body does not respond. This is a drive by wire throttle.

mis3

I did the followings in the past few months, not sure if any of these activities triggered the hesitations.

1. ATF pan flush twice (Feb-14, Apr-24)
2. Installed metallic pedals (3 months ago)
3. Engine compartment cleaning, wiped down with water and applied Meguiars Ultimate Protectant (3 weeks ago, engine cover never removed).

My problem started 2 weeks ago and it happened so far 4-5 times (not a lot). One time was real bad when I stopped at the light, the other times it just hesitated and corrected itself.

Does this kind of problem get worse as time goes by?

Glyn M Ruck

If it's the TPS it will slowly deteriorate. It's a Hall sensor.

I hope that none of the cleaning/shining products that you used under the hood contained silicone. If silicone is ingested by the engine it will poisen the O2 sensors. Never use sprays/products containing silicone under the hood.

mis3

Where is the O2 sensor? I did not remove the engine cover.

Defective O2 sensor or TPS should give a fault code, right?

The issue did not occur in the last 2 days. When the gas tank is near empty, I will put in a techron fuel injector cleaner.

Maybe it's temp related, the past 2 days were quite cool.

Glyn M Ruck

Yes you should get codes. TPS sometimes needs to be really bad to throw codes. The TPS is dual circuit.

The O2 sensors are either side of the primary Cats on the exhaust.

mis3

So, these O2 sensors are underneath the car. I definitely did not touch them during the cleaning of the engine compartment.

Just curious, I checked with the dealership:
Accelerator pedal sensor $274 CAN, this is the whole gas pedal assembly
Slide Electronic Gas Actuator $1,572 CAN, this is the throttle body

The parts guy said that the pedal has to come from Vancouver and throttle body has to come from Germany. It is not common to replace these parts.

Glyn M Ruck

Yes the O2 sensors are semi underneath the car. I'm talking about the engine ingesting silicone spray through the enginbe air intake system via the aircleaners & MAF that will poisen the O2 sensors.

Throttle bodies usually last the life of the car - not so the TPS.

mis3

I have been driving the car for the last few days and there was no hesitations anymore. Yesterday and today are hot (27-30c), the running temp as shown in the cluster is 100c.

I will monitor this and hope it does not happen again. Maybe it it was just a bad batch of fuel.