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MG MGF Technical - Engine revs slow to fall off - possible causes?

I'm not sure if I've got the terminology correct but let me try to describe the symptoms and see if any of you folks can help.

My VVC doesn't seem to be performing quite the way it should. It seems a bit lack-lustre and doesn't pull quite as well as it used to. If you'd never driven a VVC before I don't think you'd notice it.
Also, the revs don't seem to fall off as quick as they should when I take my foot off the pedal. This also shows up through a lack of engine braking.

There are no fault codes logged in the ECU. Fuel economy seems unaffected.
Russell Parslow

duff temp sensor or dirty contacts - open engine bay, find brown sensor, unclip, spray cleaner (from maplin), clip and unclip a few times, repeat a few times. See if that helps (total cost £2.50)
Will Munns

I replaced that a while ago as the engine was always fast idleing. The sensor obviously was falsely reporting that the engine was cold.

Symptoms are differnt this time.
I'll give it a try, of course, but i'm doubtful that it will help.
Russell Parslow

Hi Russell,

Rob Bell has a checklist of throttle problems on his website (under "throttle bodies") that you might want to look at.

I had similar symptoms and replaced the throttle body on my '99 VVC, which helped - but not until a couple of weeks later did I think of resetting the throttle position sensor. On the first run out after resetting, the throttle response was much better and engine braking noticeably improved. I've a strict 30 limit nearby (the infamous Limehouse Link tunnel for any Londoners out there) and keeping bang on 30 in 3rd was much easier than before...

Resetting the TPS is easily done: turn on ignition to position II (red lights but not running), fully depress and release accelerator 5 times in 20 secs, switch off. It's quick (and free) so worth trying?

Will
Will Harvey

Thanks for the help but I've tried that.
I'll check Robs site again though to make sure I'm up-to-date.
Please keep the suggestions coming! Anyone?
Power loss throughout the rev range, revs slow to fall to idle and less engine braking than normal.
Russell Parslow

I had this along with High Idle problems. I cleaned the Temp sensor contacts, the IACV contacts, MEMS/ECU contacts, Basically every electrical contact I could get to without taking off the engine bay cover. Worked a treat. I assume you have checked that the Throttle Bodyd is not sticking. If you have the old plastic one they can warp over time.

HTH

Phil
Phil Brindley

It was much better today. Seems to be intermittant so i'll just have to check all the electrical contacts. I think it might be related to the VVC controls so I'll clean them up too. I thoughted they'd have shown up in the ECU Fault log. :o(
Thanks for the suggestions.
Will be using Tom's Caterham 7 VVC Engine Loom Wiring at http://homepage.swissonline.ch/TomsSeven/
Russell Parslow

This thread was discussed between 08/08/2005 and 09/08/2005

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