Talk Morgan

Revs not going to idle

Posted By: donaldosaurus

Revs not going to idle - 22/08/20 12:26 PM

Hello fellow three wheelers,

I am noticing a reluctance for engine to reduce to idle. When changing gear it does not reduce revs despite throttle being lifted off. Stranger still I stopped after a run and was still at 3000 revs.

Only done 400 miles and I remember early cars had throttle cable with a big bend above engine but maybe the cowl for fan modification causes a poor route?
Posted By: Bitsobrits

Re: Revs not going to idle - 22/08/20 04:14 PM

Cable routing, unless done with insufficient radii, is unlikely to be the culprit, as if done wrong it would have been apparent from day 1.

Don't discount a sticking throttle pedal. The non sealed footwells and under dash area of the M3W allow all sorts of dust and debris into the pedal area.

After a newly developed issue this spring with a slightly high (1200-1400rpm) idle, a bit of sleuthing revealed the throttle cable had zero slack at the throttle body (there should be just a small but discernible amount) and traced the issue back to a sticking pedal. A bit of spray oil at the pedal pivot later, the pedal was freed off and normal idle returned.

One of my many winter projects this year will be to remove and clean/plate/repaint the pedal assembly and see if I can't come up with simple mods to facilitate periodic lubrication of the pedal pivots without standing on ones head.
Posted By: planenut

Re: Revs not going to idle - 22/08/20 04:34 PM


If the throttle cable seems to be working correctly the problem could be with the Idle Air Control. It sits on the top of the throttle body with a plug going to it. They can be cleaned but that is unlikely to be the problem with your almost new car and it will be a back to the dealer job for warranty work I expect.
Posted By: TheScottFraser

Re: Revs not going to idle - 23/08/20 12:34 AM

I agree with above. Start by cleaning the idle air control valve and the passage in the throtle body it sits in. I use q-tips to clean this so I don't spray crap down the i take into the engine.
Posted By: Bluebricked

Re: Revs not going to idle - 23/08/20 01:57 AM

I also have this problem on occasion. Except with my car the idle is a bit higher than normal and rougher and occurs both at the stoplight or when shifting gears. A blip of the throttle usually works to calm it down at the stoplight.

So it sounds like I need to check the throttle cable slack, gas pedal pivot point, and clean or replace the idle air control valve.
Posted By: donaldosaurus

Re: Revs not going to idle - 23/08/20 02:17 PM

Many thanks for input. Pedal seems to move smoothly. Cleaned sensor. Not much slack in cable. Still the same. Frustrated
Posted By: Chris99

Re: Revs not going to idle - 23/08/20 02:29 PM

Originally Posted by Bluebricked
I also have this problem on occasion. Except with my car the idle is a bit higher than normal and rougher and occurs both at the stoplight or when shifting gears. A blip of the throttle usually works to calm it down at the stoplight.

So it sounds like I need to check the throttle cable slack, gas pedal pivot point, and clean or replace the idle air control valve.


Mine had similar symptoms - turned out to be a frayed throttle cable at the throttle body end causing the throttle to stick open slightly.

If it is this and it gets worse then eventually the throttle will stick open and once you switch the engine off and try to restart it the fuel pump will run, the engine will turn over but it won't fire up.
Posted By: Bitsobrits

Re: Revs not going to idle - 23/08/20 10:15 PM

Two more ideas:

verify the cable is properly routed at the throttle body. If the throttle is opened manually for a cleaning or inspection, the cable can come out of the groove in the 'disc' on the side of the throttle body.

when the high idle situation occurs, shut off the machine and without touching the throttle, remove the air cleaner to inspect the position of the throttle plate (which should be totally closed).
Posted By: donaldosaurus

Re: Revs not going to idle - 04/09/20 12:02 PM

I thought it was throttle cable but dealer found sticky butterfly valve . Replacement cable still not arrived from MMC!

G56 wings arrived today!!!
Posted By: LightSpeed

Re: Revs not going to idle - 04/09/20 12:28 PM

Sticky throttle body probably from oil/gunk being pumped into the throttle body from the cam chest vent tube.
Posted By: donaldosaurus

Re: Revs not going to idle - 04/09/20 01:12 PM

Could well be, car has sat for a year or so before I got it. Raining now but not for long I hope. Now when weather is nice I’m cycling 300 miles this month for Cancer Research . Fundraising going well but sore ar5e!!

https://fundraise.cancerresearchuk.org/page/ians-cycle-300-fundraising-page-171

Raffling a 4.5 litre bottle of Really Big Peat too.
Posted By: PaulM3W

Re: Revs not going to idle - 19/06/22 02:04 AM

Hey all, similar issue at the moment, rpm remains high during gear changes and on stopping sometimes takes time for rpm to decay to idle. Definitely worse when engine is hot. (Ambient temp was 14 degrees C so not exactly a hot day!) Throttle cable moving freely, hard to tell if the butterfly is sticking while driving but when moved by pressing with my thumb it returns strongly to the closed position...I have cleaned the idle air control valve which was gunky and still has some baked on black stuff that has not wiped off. Will see how the next drive goes...
Posted By: Michael H

Re: Revs not going to idle - 19/06/22 06:51 PM

This happened to me last year. The spring behind the gas pedal broke. The spring at the top of the motor is not strong enough to do the job itself. I replaced the. lower spring with a 'close enough' spring and life resumed like normal. It is a pain to do as you have to go through the access hole above the assembly and hope your wrist and fingers are flexible and strong enough to do the job.
Posted By: Bluebricked

Re: Revs not going to idle - 24/06/22 03:55 AM

I have been chasing a similar problem for a while. The engine sometimes took some time to return to idle at a stop and between shifts things could get lumpy as the engine hunted around for what RPM it really wanted to be at. Finally found the right guy who was a former S&S-sponsored racer who said my TPS (Throttle Position Sensor) needed to be adjusted. He manually adjusted the sensor while watching the readouts on the S&S software and my car is back to a perfect tune. I guess there are throttle stops that wear over time and can throw things kind of out of wack. You can't visually confirm anything is worn, because the throttle snapped back and close perfectly. Except my RPMs were not decaying to an idle and RPMs sometimes remained high between shifts. Hope this helps.
Posted By: LightSpeed

Re: Revs not going to idle - 24/06/22 01:40 PM

Originally Posted by Bluebricked
I have been chasing a similar problem for a while. The engine sometimes took some time to return to idle at a stop and between shifts things could get lumpy as the engine hunted around for what RPM it really wanted to be at. Finally found the right guy who was a former S&S-sponsored racer who said my TPS (Throttle Position Sensor) needed to be adjusted. He manually adjusted the sensor while watching the readouts on the S&S software and my car is back to a perfect tune. I guess there are throttle stops that wear over time and can throw things kind of out of wack. You can't visually confirm anything is worn, because the throttle snapped back and close perfectly. Except my RPMs were not decaying to an idle and RPMs sometimes remained high between shifts. Hope this helps.


Good info to know.
Posted By: PaulM3W

Re: Revs not going to idle - 25/06/22 02:40 AM

Hey all,
Results of my rest drive were very pleasing. After cleaning the gunk off the idle air control valve rpm decay is normal again! I actually noticed that I had slowly been adjusting my driving to compensate for the slow rpm decay, I am back to blipping the throttle on gear changes!
Posted By: nippymog

Re: Revs not going to idle - 25/06/22 09:30 AM

Could you describe or have a picture of where the idle air control valve is please?
Sorry , it is described clearly above doh
I must read posts properly !
Posted By: nippymog

Re: Revs not going to idle - 03/07/22 02:40 PM

I also have occasional slow return to idle, and have just got round to checking it.
I have checked the throttle linkage etc and all seems ok , so I want to check the Idle Air control described above as being on top of the throttle body.

Is it this ?

[Linked Image]

If so what do I clean? it all seems clean to me !

[Linked Image]

Thanks
Posted By: R1NGA

Re: Revs not going to idle - 03/07/22 02:58 PM

That is indeed the ICV. Not easy to clean, but I use aresol Carb Cleaner to blast stuff out. Be careful not to try to dismantle as the plunger is under spring pressure and if it fires off you mauy never see it again. Also clean the inside of the plenum/inlet manifold to clear gunt too.
Posted By: LightSpeed

Re: Revs not going to idle - 03/07/22 03:17 PM

The cam chest puking oil up into the throttle body sure does not help keep that clean.
Posted By: nippymog

Re: Revs not going to idle - 03/07/22 03:21 PM

Thanks both.
Just wiped it down with a clean cloth and tested it electrically connected but not fitted so I could see the plunger work , which it did.
Reassembled and tickover seemed fine , so pending a trial run I am calling it.

Postscript : tickover now fine. My gut feel is simply breaking and making the connector sorted mine out.
Googling the part number on the Air Control valve itself ( 228W8569S ) gave this , which visually looks identical , and if it plays up again for 11 quid is worth a punt. Has anyone else tried this part ?
https://www.autodoc.co.uk/ridex/814...lPitb_L7SYhLolaEF7y1Em-Ur_RoCszUQAvD_BwE
Posted By: Bunny

Re: Revs not going to idle - 04/07/22 10:37 AM

You could pay £11 or you could pay substantially more to have the S&S name associated with it!

[Linked Image]
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