The 75 and ZT Owners Club Forums - View Single Post - High idle MG-ZT 190, idle doesn't come down after releasing throttle

Savestones · 17th June 2022, 16:44

Back again with a new issue

The throttle on my ZT seemed to stick a bit, leading to the lubing of the throttle cable. This seemed to fix the problem for a while, up to the point that I got a replacement key made.

Driving away from the garage that made my replacement key, swifting from 1st to 2nd gear I saw my revs increasing with my throttle fully up and my clutch on the floor. At this point I thought it was the throttle cable again. I tried to push the throttle pedal up from below, but it was already fully up. Also, pushing with the revs climbing did not lead to a decrease in revs. At this point, revs would climb but fall back down again after a few seconds.

Kept driving, problem seemed to fix itself. Talking to a friend about it, he suggested cleaning out the idle control valve. Good suggestion, so I did that the first time I got the chance. Had no problems before cleaning, no problems after.

All was well until I got my wheels aligned. After my one hour appointment, driving away I again had the revs climbing when the clutch was down. Again, revs would climb and then fall back down on their own within a couple of seconds. This is the point where I casually started looking for a new idle control valve.

Car went back to running fine. Cue to today: Picked up my friend from the doctors. At the start of this 20-minute journey, revs would climb ~200 rpm when shifting gears. Annoying, but manageable. On the way back, my ZT would idle at ~3000 rpm. While driving, when depressing the clutch to downshift, revs would climb seemingly without a limit. Also, the car keeps slowly speeding up while not pressing the gas.

I just went back to car after it had sat for a while. Resetting the ICV by pressing the throttle 5 times with the keys in position 2 did nothing. The car now idles at ~2000 rpm, and when I press the gas revs climb and won't fall back down after letting my foot of the gas.

This has basically made my car undriveable, as there is now way to drive the car safely at low speeds (without wrecking the engine by letting the revs climb to 5000).

Am I right in assuming that the issue is with the ICV, or could it still be a problem with the throttle cable? Also, is there any further test I can do now before replacing the ICV or other parts?

Much appreciated as always!

17th June 2022, 16:44	#1
Savestones Regular poster MG ZT-T Join Date: Dec 2021 Location: Arnhem, Netherlands Posts: 62 Thanks: 10 Thanked 6 Times in 6 Posts	High idle MG-ZT 190, idle doesn't come down after releasing throttle Back again with a new issue The throttle on my ZT seemed to stick a bit, leading to the lubing of the throttle cable. This seemed to fix the problem for a while, up to the point that I got a replacement key made. Driving away from the garage that made my replacement key, swifting from 1st to 2nd gear I saw my revs increasing with my throttle fully up and my clutch on the floor. At this point I thought it was the throttle cable again. I tried to push the throttle pedal up from below, but it was already fully up. Also, pushing with the revs climbing did not lead to a decrease in revs. At this point, revs would climb but fall back down again after a few seconds. Kept driving, problem seemed to fix itself. Talking to a friend about it, he suggested cleaning out the idle control valve. Good suggestion, so I did that the first time I got the chance. Had no problems before cleaning, no problems after. All was well until I got my wheels aligned. After my one hour appointment, driving away I again had the revs climbing when the clutch was down. Again, revs would climb and then fall back down on their own within a couple of seconds. This is the point where I casually started looking for a new idle control valve. Car went back to running fine. Cue to today: Picked up my friend from the doctors. At the start of this 20-minute journey, revs would climb ~200 rpm when shifting gears. Annoying, but manageable. On the way back, my ZT would idle at ~3000 rpm. While driving, when depressing the clutch to downshift, revs would climb seemingly without a limit. Also, the car keeps slowly speeding up while not pressing the gas. I just went back to car after it had sat for a while. Resetting the ICV by pressing the throttle 5 times with the keys in position 2 did nothing. The car now idles at ~2000 rpm, and when I press the gas revs climb and won't fall back down after letting my foot of the gas. This has basically made my car undriveable, as there is now way to drive the car safely at low speeds (without wrecking the engine by letting the revs climb to 5000). Am I right in assuming that the issue is with the ICV, or could it still be a problem with the throttle cable? Also, is there any further test I can do now before replacing the ICV or other parts? Much appreciated as always!