engine revving at idle
06-20-2003, 07:27 PM
#26
Super Member
Join Date: May 2002
Location: SF South Bay
Posts: 844
Likes: 0
Received 1 Like
on
1 Post
2002 C230 Coupe
Stop the "go to read how things work" thing. I don't know how things in the old days work and how things in the new days work. The only thing I know is that, for my car, when I set the cruise on and shift to neutral, the RPM and speed goes down. How can your theory explain this to me? I know there is theory and practice. If you say there is a glitch in my car's electronic system that makes it not to over-rev, I'm happy 
.
.
06-20-2003, 10:31 PM
#27
MBWorld Fanatic!
Join Date: May 2002
Location: The blue white rock, third out.
Posts: 2,916
Likes: 0
Received 1 Like
on
1 Post
2002 C230 Coupe(M111)
Every other standard shift car that Ive owned with cruise control, will rev if the cruise is on, and you take it out of gear. If you push in the clutch first, then the cruise de- activates.
Haven't tried this yet on the MB....but then it hasn't left the garage lately with all this nice weather. I'll agree with DCX about the need for cruise at low speed- there's plenty of cop infested roads around here with 30 or 40mph limits on them on my ride home. Hell, I even use the cruise on my bike on some of them...its nice to just chill on those roads. Try putting the cruise on sometime, you'll be surprised how much your mileage goes up. I used that and coasting down the hills one day...got 40mpg on the 12.5 mile ride home- and no it wasn't on the highway.. Kinda geeky, but fun
Haven't tried this yet on the MB....but then it hasn't left the garage lately with all this nice weather. I'll agree with DCX about the need for cruise at low speed- there's plenty of cop infested roads around here with 30 or 40mph limits on them on my ride home. Hell, I even use the cruise on my bike on some of them...its nice to just chill on those roads. Try putting the cruise on sometime, you'll be surprised how much your mileage goes up. I used that and coasting down the hills one day...got 40mpg on the 12.5 mile ride home- and no it wasn't on the highway.. Kinda geeky, but fun
06-21-2003, 12:55 AM
#28
Super Member
Join Date: May 2002
Location: SF South Bay
Posts: 844
Likes: 0
Received 1 Like
on
1 Post
2002 C230 Coupe
Originally posted by Outland
Every other standard shift car that Ive owned with cruise control, will rev if the cruise is on, and you take it out of gear. If you push in the clutch first, then the cruise de- activates.
Every other standard shift car that Ive owned with cruise control, will rev if the cruise is on, and you take it out of gear. If you push in the clutch first, then the cruise de- activates.
06-21-2003, 01:11 PM
#30
Member
Join Date: Sep 2002
Location: MI
Posts: 207
Likes: 0
Received 0 Likes
on
0 Posts
2003 C230K, 6 spd, Brilliant Silver, C-5, C-7, CD changer
Originally posted by mctwin2kman
Update: I just tested mine and it does rev up to attempt to hold the cruise speed after a shift to nuetral. I would assume this is because the car computer still has the cruise set and assumes the driver would have shifted into a gear not nuetral. Although I am still trying to mentally figure out why anyone would shift to nuetral with the cruise set anyway, I am at a loss on how to explain this any further. Cruise used to cancel when the clutch was depressed on other vehicles as I verified this with a man who has driven far more standard shift vehicles than I and for far longer than I. He is a few years older, like 25, so I would believe him on this one. But for validation of this so called problem, I do not think this is an issue since no one should be driving in nuetral with the cruise on anyhow, that it happens in my vehicle as well. Am I going to rush to the dealer for a fix? No, because it is working as it should.
Update: I just tested mine and it does rev up to attempt to hold the cruise speed after a shift to nuetral. I would assume this is because the car computer still has the cruise set and assumes the driver would have shifted into a gear not nuetral. Although I am still trying to mentally figure out why anyone would shift to nuetral with the cruise set anyway, I am at a loss on how to explain this any further. Cruise used to cancel when the clutch was depressed on other vehicles as I verified this with a man who has driven far more standard shift vehicles than I and for far longer than I. He is a few years older, like 25, so I would believe him on this one. But for validation of this so called problem, I do not think this is an issue since no one should be driving in nuetral with the cruise on anyhow, that it happens in my vehicle as well. Am I going to rush to the dealer for a fix? No, because it is working as it should.
What were the parameters you tried this with?
My car is a 2003 as well and after checking the version coding, the dealer thinks it may be wrong. In other words, the car may not know what it is. This is unconfirmed at this point as they are waiting for a response from MB tech. I have my doubts about the version coding thing, as I think it would happen all the time, but time will tell.
06-21-2003, 01:23 PM
#31
Member
Join Date: Sep 2002
Location: MI
Posts: 207
Likes: 0
Received 0 Likes
on
0 Posts
2003 C230K, 6 spd, Brilliant Silver, C-5, C-7, CD changer
Originally posted by mctwin2kman
Unless there have been some severe transmission enhancements in the last few years there is no way to see nuetral on a standard shift tranny. There are no sensors to tell you the gear and last I saw the only sensor in the darn things may be a fluid sensor, but I have not seen them either. This is why a standard shift tranny is so much less money, there is no advanced tech in one.
Unless there have been some severe transmission enhancements in the last few years there is no way to see nuetral on a standard shift tranny. There are no sensors to tell you the gear and last I saw the only sensor in the darn things may be a fluid sensor, but I have not seen them either. This is why a standard shift tranny is so much less money, there is no advanced tech in one.
Originally posted by mctwin2kman
GO read how stuff works and you will see that there is not a whole lot to a tranny. In the old days the clutch killed the cruise so maybe it is a fluke that our cars even hold the cruise when the clutch is depressed. There should never be a need to shift with the cruise set, as you shoudl be cruising.
GO read how stuff works and you will see that there is not a whole lot to a tranny. In the old days the clutch killed the cruise so maybe it is a fluke that our cars even hold the cruise when the clutch is depressed. There should never be a need to shift with the cruise set, as you shoudl be cruising.
06-21-2003, 01:26 PM
#32
MBWorld Fanatic!
Join Date: May 2002
Location: The blue white rock, third out.
Posts: 2,916
Likes: 0
Received 1 Like
on
1 Post
2002 C230 Coupe(M111)
Originally posted by 20FHK02
Generally speaking, how can you shift out of gear without pushing the clutch first??
Generally speaking, how can you shift out of gear without pushing the clutch first??
Drag racers sometimes try this to save time between shifts. It requires a strong arm to do it when the throttle is down, and no , its not good for the transmission.
06-21-2003, 01:47 PM
#33
Super Member
Join Date: May 2002
Location: SF South Bay
Posts: 844
Likes: 0
Received 1 Like
on
1 Post
2002 C230 Coupe
Originally posted by Outland
Just push on the lever. There's nothing holding it in. Believe it or not, you don't need the clutch to shift gears. Just pull it out of gear, and then apply light pressure putting it into the next higher gear- if your off the gas it should pop in within a couple of seconds.
Drag racers sometimes try this to save time between shifts. It requires a strong arm to do it when the throttle is down, and no , its not good for the transmission.
Just push on the lever. There's nothing holding it in. Believe it or not, you don't need the clutch to shift gears. Just pull it out of gear, and then apply light pressure putting it into the next higher gear- if your off the gas it should pop in within a couple of seconds.
Drag racers sometimes try this to save time between shifts. It requires a strong arm to do it when the throttle is down, and no , its not good for the transmission.
06-21-2003, 02:38 PM
#34
Super Member
Originally posted by Outland
Just push on the lever. There's nothing holding it in. Believe it or not, you don't need the clutch to shift gears. Just pull it out of gear, and then apply light pressure putting it into the next higher gear- if your off the gas it should pop in within a couple of seconds.
Drag racers sometimes try this to save time between shifts. It requires a strong arm to do it when the throttle is down, and no , its not good for the transmission.
Just push on the lever. There's nothing holding it in. Believe it or not, you don't need the clutch to shift gears. Just pull it out of gear, and then apply light pressure putting it into the next higher gear- if your off the gas it should pop in within a couple of seconds.
Drag racers sometimes try this to save time between shifts. It requires a strong arm to do it when the throttle is down, and no , its not good for the transmission.
06-22-2003, 01:27 PM
#36
MBWorld Fanatic!
Join Date: May 2002
Location: The blue white rock, third out.
Posts: 2,916
Likes: 0
Received 1 Like
on
1 Post
2002 C230 Coupe(M111)
Originally posted by mdp c230k
Its called 'speed shifting' and it is fine for the tranny if you know what you are doing. From your decription you do not know how to do it right. It is done by matching engine rpm needed to slide into the next gear. Basically, matching the engine's speed to the tranny's at which point the shifter will smoothly slide right into gear with very little pressure. If you are on a flat section of road try using just enough gas to not change speed then move the stick and it will come out of gear with great ease. If there is any load on the tranny it wont be easy to move the stick. It is done more to save clutch wear than time.
Its called 'speed shifting' and it is fine for the tranny if you know what you are doing. From your decription you do not know how to do it right. It is done by matching engine rpm needed to slide into the next gear. Basically, matching the engine's speed to the tranny's at which point the shifter will smoothly slide right into gear with very little pressure. If you are on a flat section of road try using just enough gas to not change speed then move the stick and it will come out of gear with great ease. If there is any load on the tranny it wont be easy to move the stick. It is done more to save clutch wear than time.
Speed shifting, power shifting, whatever. When your shifter forks are bent beyond belief from doing this drag racing, let us know how its not hurting the car. The synchros take a pounding as well.
Last edited by Outland; 06-22-2003 at 01:32 PM.
06-23-2003, 09:57 AM
#37
MBWorld Fanatic!
Join Date: Aug 2002
Location: York, PA
Posts: 2,753
Likes: 0
Received 0 Likes
on
0 Posts
2003 C230K Sport Coupe, 1986 190E 2.3
DCX I tried it at 70 and it did rev up, but the funny thing is I tried it at 40 earlier and it did not do the rev'ing up thing. SO I am utterly confused as to why. I set the cruise at 70 in 4th gear and then waited about 30 seconds. Then I pushed in the clutch and shifted to nuetral, and released the clutch. Then after about 3-5 seconds the car rev'ed to almost the limiter before it gave up and disengaged the cruise. This did not happen at 40, but maybe I did not have the cruise engaged long enough. The only reason I see that it does not disengage the cruise as I would expect is for downshifting while going up hill to maintain speed, but I am not sure why this does not happen on a 2002. Maybe diferent software in the engine controller, but I am not sure. Next time I have the car I will test further at low speeds, my wife has it all week I only get it on Friday's. Once in a while she allows me to drive it other days, what can I expect out of my car.... Keep us informed if this really is a problem or just some software change they made between model years. To be honest that is the first time I have ever tried this, but I did test the cruise to see if it stayed engaged while the clutch was in for a shift in the past and it did.
06-23-2003, 07:16 PM
#38
MBWorld Fanatic!
Thread Starter
Join Date: Jul 2002
Location: Peoria IL
Posts: 1,750
Likes: 0
Received 0 Likes
on
0 Posts
2003 MB C230 coupe
well, my car was at the dealership for 6 days (while i was out of town) and it's still not fixed. they rechecked all the wiring, check for any diagnostic codes and test drove it for several days and declared it to be fine. and it's doing it just as bad as ever today.
what does everyone else's do at idle. it should just stick at one RPM all the time at idle right? should waver at all right? i can't even remember anymore.
i don't know what to do cause i don't know how they would be able to fix something like this.
what does everyone else's do at idle. it should just stick at one RPM all the time at idle right? should waver at all right? i can't even remember anymore.
i don't know what to do cause i don't know how they would be able to fix something like this.
06-23-2003, 07:47 PM
#39
MBWorld Fanatic!
Thread Starter
Join Date: Jul 2002
Location: Peoria IL
Posts: 1,750
Likes: 0
Received 0 Likes
on
0 Posts
2003 MB C230 coupe
okay, i've been doing some research and i've found that the most common thing that causes revving at idle is a bad or sticky idle air control (IAC) valve. can someone back this up? now i just need to make the dealership take a look at it and actually do something about it.
06-24-2003, 01:19 AM
#40
Member
Join Date: Sep 2002
Location: MI
Posts: 207
Likes: 0
Received 0 Likes
on
0 Posts
2003 C230K, 6 spd, Brilliant Silver, C-5, C-7, CD changer
Originally posted by truelove
okay, i've been doing some research and i've found that the most common thing that causes revving at idle is a bad or sticky idle air control (IAC) valve. can someone back this up? now i just need to make the dealership take a look at it and actually do something about it.
okay, i've been doing some research and i've found that the most common thing that causes revving at idle is a bad or sticky idle air control (IAC) valve. can someone back this up? now i just need to make the dealership take a look at it and actually do something about it.
It's possible they don't even use IAC with the electronic throttle as they have very precise control over the air metering using software in the control unit.
So, does it just waver up and down a small amout slowly?
Or does it rev quickly with enough power to lurch the car?
It could be IAC *if* there is one and the change is relatively small, or the ECU controlling the IAC is wacked, or the ECU is getting bad info from another sensor (or bad harness) into it causing it to react incorrectly, or the electronic throttle/controller could be in the same situation.
I'm sure that's clear as mud!
06-24-2003, 08:38 AM
#41
MBWorld Fanatic!
Thread Starter
Join Date: Jul 2002
Location: Peoria IL
Posts: 1,750
Likes: 0
Received 0 Likes
on
0 Posts
2003 MB C230 coupe
no it's not revving enough to really move the car at all. of course it can't cause it only does it out of gear anyway. it only wavers a few hundred RPM, sometimes slowly, sometimes quickly.
