OK, here we go again.
In continuation to this thread, http://www.benzworld.org/forums/c209-a209-clk-class/2652410-bad-throttle-pedal.html, I have similar symptoms again, but they appear intermittently. Let me describe exactly what I get, so you have a more clear picture. I know it's gonna be long, but I want to present the full story.
One morning, like a month ago, that I first started the car I noticed that the RPM would not go to 1100-1200 as every morning, but rather dropped to 600-800 immediately. I did not pay much attention, but when I pulled over I noticed that the engine had some hesitation to accelerate, though the pedal seemed to be responsive, i.e. pressing more on the pedal seemed to give the command to accelerate, but the engine was somehow hesitant to do so, as if I was using both the brake and the throttle pedal at the same time. I immediately remembered that the day before I made a long trip with the car and on the return leg I had refuelled. I then suspected that the gas I put in was bad. After switching off the engine and back on and going for a short trip on the freeway while running the engine at 3000-4000 between times, the problem seemed to have gone away and everything was normal again. The issue never reappeared, until 12 days ago (Thursday, March 9). On that day, the car was fine from morning till night, until I went over a few speed bumps. Seconds later, the engine begun again not revving up fast enough according to the throttle pedal inputs, but it would still go up to high RPM if I selected a specific gear. I mean, if I selected, say the 3rd gear, the engine would rev up to high RPM, but it did slowly, as if the throttle pedal input was very minor, though I was almost pressing it fully. I found it strange that this happened as soon as I went over a speed bump. I thought that I was unlucky again with the gas, as I had refuelled 5-6 days before, and I thought that the speed bumps somehow caused the gas in the tank to move and mix, possibly allowing some bad gas leftovers to pass through. I pulled over, switched off and on, everything was fine. Next morning, the same thing happened with the low RPM in the first start, and after switching off and on the engine, all back to normal.
On Sunday (12 March), the car started fine, but guess what, as soon as I went over a speed bump, the same hesitation appeared again... Switch off, back on, everything OK.
Please note here that I had no other issues, i.e. no CEL, shifting was smooth, no excessive fuel consumption, no rough idle, and when I say no rough idle, I mean the engine is so smooth you can hardly tell if it's running or not, especially when at operating temperature, and regardless of P,R,N,D. I was really puzzled.
Another full week passed without any issues whatsoever, until - guess what - I went over another speed bump!!! :eek Note that in all this interval I hadn't refuelled. This time, I felt both the acceleration hesitation, and also unresponsiveness from the throttle pedal. I pulled over and put the car in neutral. Pressing the pedal was very unresponsive, it would rev up the engine very very slowly and 5-6 seconds after I had really put my foot on the pedal. These are exactly the same symptoms I had when the previous throttle pedal was going bad. I decided to hook up my $20 dollar OBD reader, which showed the code P0121 - Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance Problem. Hmmm, something is suspicious here... After restarting the engine, yes, everything was back to normal... I still had no CEL. This day was Friday, 17 March.
Friday evening when returning home from work, I noticed the same unresponsiveness from the throttle pedal.
On Saturday, the car started fine. I decided to put some gas in, though the tank was still half way full. On the return leg, the unresponsiveness came back in a rather severe way. The engine was hardly responding to the pedal's input commands, making the car almost impossible to drive. I drove home carefully, and when monitoring my fuel consumption indicator, fuel consumption still looked normal to me, despite pressing the pedal almost full way in order to get the engine to rev up.
On Sunday it was the same story again, with low responsiveness/acceleration, switch off and back on all back to normal.
Yesterday, the car behaved completely fine.
From all the above, I concluded that it was either the throttle pedal going bad again, or I got really unlucky with bad gas, or a combination of the two, which is actually a rather rare coincidence, I would say.
The new throttle pedal that was installed in the car was an aftermarket HELLA (if I remember correctly), though I insisted to my mechanic to install an OEM one.
I called my mechanic and argued that the throttle pedal he installed was faulty, and he told me to bring the car in. I took it today morning ( the car was running fine by the way), and he confirmed with his diagnostic the P0121 code. His diagnostic said "Accelerator pedal sensor", but there was also another message regarding the M16/6 module (throttle valve actuator) and some bad value on its potentiometer ( or something like that, I don't fully remember the message). These were the only codes that were stored. The mechanic tried to convince me that it's the throttle body at fault and not the throttle pedal.
I asked if there would be a different code if it was the throttle body itself and he said that all these are connected and one gets the same code for both components. I found it hard to believe, and I suspected that the message on the M16/6 module was due to the pedal not sending correct inputs. Anyway, I decided not to do anything until I get a second opinion. On the way to work after a short stop for groceries I got the unresponsiveness again... :banghead:
At some point I worried that there might be something wrong with the fact that I replaced my spark plugs around 3 weeks before the first symptoms appeared, but in that case wouldn't I get misfires and/or other related issues? I mean, the engine runs silk smooth even when the issue is present...
Finally, note that I experienced this acceleration hesitation twice, like a year ago, with around 2-3 months interval time and it was again right after refuelling, both times. The first time, I took the car in, there were no codes stored and the mechanic cleaned the throttle body as preventive maintenance and claimed that it was bad fuel. The second time I didn't pay much attention because I was sure it was yet another bad refill. These two times the issue happened only once, with no recurrence between them.
I hadn't experienced this hesitation again until now.
I apologise for the long post.
I'd be very glad for any input related to this issue.
Chris
In continuation to this thread, http://www.benzworld.org/forums/c209-a209-clk-class/2652410-bad-throttle-pedal.html, I have similar symptoms again, but they appear intermittently. Let me describe exactly what I get, so you have a more clear picture. I know it's gonna be long, but I want to present the full story.
One morning, like a month ago, that I first started the car I noticed that the RPM would not go to 1100-1200 as every morning, but rather dropped to 600-800 immediately. I did not pay much attention, but when I pulled over I noticed that the engine had some hesitation to accelerate, though the pedal seemed to be responsive, i.e. pressing more on the pedal seemed to give the command to accelerate, but the engine was somehow hesitant to do so, as if I was using both the brake and the throttle pedal at the same time. I immediately remembered that the day before I made a long trip with the car and on the return leg I had refuelled. I then suspected that the gas I put in was bad. After switching off the engine and back on and going for a short trip on the freeway while running the engine at 3000-4000 between times, the problem seemed to have gone away and everything was normal again. The issue never reappeared, until 12 days ago (Thursday, March 9). On that day, the car was fine from morning till night, until I went over a few speed bumps. Seconds later, the engine begun again not revving up fast enough according to the throttle pedal inputs, but it would still go up to high RPM if I selected a specific gear. I mean, if I selected, say the 3rd gear, the engine would rev up to high RPM, but it did slowly, as if the throttle pedal input was very minor, though I was almost pressing it fully. I found it strange that this happened as soon as I went over a speed bump. I thought that I was unlucky again with the gas, as I had refuelled 5-6 days before, and I thought that the speed bumps somehow caused the gas in the tank to move and mix, possibly allowing some bad gas leftovers to pass through. I pulled over, switched off and on, everything was fine. Next morning, the same thing happened with the low RPM in the first start, and after switching off and on the engine, all back to normal.
On Sunday (12 March), the car started fine, but guess what, as soon as I went over a speed bump, the same hesitation appeared again... Switch off, back on, everything OK.
Please note here that I had no other issues, i.e. no CEL, shifting was smooth, no excessive fuel consumption, no rough idle, and when I say no rough idle, I mean the engine is so smooth you can hardly tell if it's running or not, especially when at operating temperature, and regardless of P,R,N,D. I was really puzzled.
Another full week passed without any issues whatsoever, until - guess what - I went over another speed bump!!! :eek Note that in all this interval I hadn't refuelled. This time, I felt both the acceleration hesitation, and also unresponsiveness from the throttle pedal. I pulled over and put the car in neutral. Pressing the pedal was very unresponsive, it would rev up the engine very very slowly and 5-6 seconds after I had really put my foot on the pedal. These are exactly the same symptoms I had when the previous throttle pedal was going bad. I decided to hook up my $20 dollar OBD reader, which showed the code P0121 - Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance Problem. Hmmm, something is suspicious here... After restarting the engine, yes, everything was back to normal... I still had no CEL. This day was Friday, 17 March.
Friday evening when returning home from work, I noticed the same unresponsiveness from the throttle pedal.
On Saturday, the car started fine. I decided to put some gas in, though the tank was still half way full. On the return leg, the unresponsiveness came back in a rather severe way. The engine was hardly responding to the pedal's input commands, making the car almost impossible to drive. I drove home carefully, and when monitoring my fuel consumption indicator, fuel consumption still looked normal to me, despite pressing the pedal almost full way in order to get the engine to rev up.
On Sunday it was the same story again, with low responsiveness/acceleration, switch off and back on all back to normal.
Yesterday, the car behaved completely fine.
From all the above, I concluded that it was either the throttle pedal going bad again, or I got really unlucky with bad gas, or a combination of the two, which is actually a rather rare coincidence, I would say.
The new throttle pedal that was installed in the car was an aftermarket HELLA (if I remember correctly), though I insisted to my mechanic to install an OEM one.
I called my mechanic and argued that the throttle pedal he installed was faulty, and he told me to bring the car in. I took it today morning ( the car was running fine by the way), and he confirmed with his diagnostic the P0121 code. His diagnostic said "Accelerator pedal sensor", but there was also another message regarding the M16/6 module (throttle valve actuator) and some bad value on its potentiometer ( or something like that, I don't fully remember the message). These were the only codes that were stored. The mechanic tried to convince me that it's the throttle body at fault and not the throttle pedal.
I asked if there would be a different code if it was the throttle body itself and he said that all these are connected and one gets the same code for both components. I found it hard to believe, and I suspected that the message on the M16/6 module was due to the pedal not sending correct inputs. Anyway, I decided not to do anything until I get a second opinion. On the way to work after a short stop for groceries I got the unresponsiveness again... :banghead:
At some point I worried that there might be something wrong with the fact that I replaced my spark plugs around 3 weeks before the first symptoms appeared, but in that case wouldn't I get misfires and/or other related issues? I mean, the engine runs silk smooth even when the issue is present...
Finally, note that I experienced this acceleration hesitation twice, like a year ago, with around 2-3 months interval time and it was again right after refuelling, both times. The first time, I took the car in, there were no codes stored and the mechanic cleaned the throttle body as preventive maintenance and claimed that it was bad fuel. The second time I didn't pay much attention because I was sure it was yet another bad refill. These two times the issue happened only once, with no recurrence between them.
I hadn't experienced this hesitation again until now.
I apologise for the long post.
I'd be very glad for any input related to this issue.
Chris