Strange problem - throttle revs itself

[repenttokyo]

After participating in a 5 hour rally this weekend, my throttle has developed an odd habit. When I am driving normally, everytime I shift gears, as soon as I put the clutch it the engine revs up about 500 rpm and then starts to drop normally. It does NOT do this if I rev it in neutral and the take my foot off the accelerator. I checked the throttle cable and it's not catching on anything....any reason why this would only happen while the car is in gear? Is there some special return spring or something?

[Ross]

Keep looking around the throttle cable I say. Maybe something binding with the engine torque.

[bill g]

Make sure the engine/transmission is not moving about excessively due to failed engine mount - this was a cause of that problem on previous car/s I have owned.

Bill G

[repenttokyo]

that is something I hadn't considered. Should I be checking for engine vibration at idle?

[repenttokyo]

would a bad engine mount ever manifest itself as a rumble sound heard only inside the car, at idle? The sound lessens as I drive, but I thought it was due to a hole in my exhaust from too much deep snow a few weeks back - now I am wondering if it is vibration from a bad mount? What is the best way to test for a bad engine mount?

[Incantation]

maybe your dk is sticking

[repenttokyo]

maybe your dk is sticking


what is a dk?


it seems to only be getting worse, especially around 2k-3k rpm. It almost only happens on upshifts, when I release the accelerator before the shift. It's almost like having cruise control on all the time. Not the safest thing in the world. I took some silicone lubricant and sprayed the throttle linkage on the side of the engine, and the throttle wire. I noticed there were 2 wires - the throttle and then another one beside it that seemed a bit loose. What is this second wire? They seem to move in tandem.

[Blitzkrieg Bob]

what is a dk?


thats a drive by wire throttle body system.

[repenttokyo]

to clarify, by "wires" i meant cables, as in throttle cable.

[Blitzkrieg Bob]

to clarify, by "wires" i meant cables, as in throttle cable.

Potentiometer on the pedal driving a motor on the throttle
Body.

You’ve got a good old fashioned boden cable. much like a bike.

[repenttokyo]

Potentiometer on the pedal driving a motor on the throttle
Body.

You’ve got a good old fashioned boden cable. much like a bike.

i know. I can see my throttle cable, and the secondary cable I am assuming is the cruise control. There don't seem to be any obstruction on the throttle cable - is it possible that somehow my cruise control is activating or binding? I am also considering that I might have an obstruction at the firewall in the driver's compartment.

This is really frustrating!

[DaveVoorhis]

A failing Throttle Position Sensor, maybe?

[repenttokyo]

Another good guess - Is the TPS easily accessible?

The thing that is most weird out of all of this is I cannot reproduce it with the clutch in or the car in neutral - the engine has to be under load.

[Blitzkrieg Bob]

Another good guess - Is the TPS easily accessible?

The thing that is most weird out of all of this is I cannot reproduce it with the clutch in or the car in neutral - the engine has to be under load.


see if you blew one out

under load the motor moves and either the intake boot moves off the throttle body or the cable gets pulled

[repenttokyo]

More diagnostic info - after playing around with it a lot last night, I found that if i am very gentle with the accelerator, it does not happen nearly as often. To me, this makes me think it could be pedal return related. Since it's been very very cold here lately (-30) I am hoping to be able to get at this problem this weekend when it should be around plus 5.

[repenttokyo]

More diagnostic info - after playing around with it a lot last night, I found that if i am very gentle with the accelerator, it does not happen nearly as often. To me, this makes me think it could be pedal return related. Since it's been very very cold here lately (-30) I am hoping to be able to get at this problem this weekend when it should be around plus 5.

[632 Regal]

motor mounts

[repenttokyo]

how do i test for a bad motor mount without getting under the car?

Also, the bentley manual doesn't have a procedure for throttle cable replacement - does anyone have a link to a write up?