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MG MGF Technical - High Rev Tickover

I could give a long story of how, about 4 months ago, I persuaded my g/f to buy a 96 MGF going pretty cheap.........a spur of the moment thing!!!

Anyway, everything was fine till we lost a radiator hose, which ended in HGF!!

Got that fixed, not by a Rover specialist (a friend who maintains a large fleet of vehicles). Things have been fine for the couple of weeks and about 1200 miles since, but today I noticed the tickover not coming down below 2000rpm, and if you try hitting the pedal it will stick up at 3000rpm for a while before dropping down to 2000 again.

Any ideas, I have tried the foot under the pedal to see if some sort of sticky cable, but that doesn't seem to help....what controls the revs?

I don't have much time before heading up to Scotland (work, fly up tomorrow!) and don't want to leave the g/f with a potential problem....she is quickly losing her sense of humour with the car....and me for the idea of getting it!

When it's running it's a great little car...loads of fun.

I would appreciate any ideas....thanks!
Sid

Hi Sid,

Firstly, let me make clear that I am by no means an expert on this subject but as you're in a hurry the first thing I would check would be the throttle body. It's accessible from the boot when you remove the the grill and sometimes can suffer from sticking. Your looking for the black plastic bit between the air box and the inlet. At the front of it is the accelorator cable. You'll see which bit I mean if someone is in the car revving whilst you look as the cable will move up and down. Just try some WD40 for example around this.
I'm sure there will be a lot more qualified than I people along very shortly with other suggestion.
HTH
Kris.
Kris Ford

Also, just remembered something else to check.
I've not heard of this on MG's before but had an experience in a previous car where the air filter was clogged and filthy and was effectively strangling the engine. This gave me very similar symptoms so may be worth checking the condition of the filter.
Kris Ford

Kris

Thanks for your quick reply.

Since the car has cooled down it seems to have cured for the moment???

I have sprayed the throttle mechanism with WD40 in any case. I wont have time to get the air filter out......I think I'd have to remove the engine cover to get at it? She did say that she though there was a little power loss, could be air filter???

I'll monitor it (maybe take the car to the airport using airport transfers tunbridge wells myself....best not take any chances, or upset her anymore!!!)

Any other suggestions still appreciated.

Thanks again
Sid

Hi Sid,

If the head has been off recently then it's possible the cable from the throttle position sensor has been knocked and is giving an intermittent connection. These seem to get fragile just over time and will break when disturbed. Next time the tickover doesn't settle remove the rear grille panel and reach in and wiggle the cable that sticks up slightly from the block connector on the TPS - if it's a broken wire you'll get a change in revs immediately.

Other possible cause is that the induction pipe has been disconnected from the throttle body during the HGF repair and done up a little too tight, possibly with a jubilee clip rather than the OE clip. This can cause the butterfly to stick slightly, although this usually can be cleared with a blip of the throttle (as you've already tried). So my money's on the wires being at fault.

Mike Hankin

Mike

Thanks for that. I will drive the car and if the problem arises again give that a go.

Thanks
Sid

Sid,

Take a look at
http://www.mgf.ultimatemg.com/group2/Throttle_body/index.htm#problem

Another possible cause is a faulty temp sender (or dirty connections to sender). Worth disconnecting, cleaning and reconnecting as it costs nothing. A new sensor is also less than £15 and easy to replace. See
http://www.mgf.ultimatemg.com/group2/common_problems/hgf_pages/related_problems_overheating.htm and scroll down to ECU temp sensor section.
Dave Livingstone

Sid

Might be worth trying to reset the stepper motor - IIRC, with warm and stopped engine - switch ignition on (don't start the engine) press the throttle down to the floor 5 times rapidly - switch ignition off for 15 seconds then start engine.

Steve
Steve P

Sid

I had this high tickover on my 2000 1.8i MGF, but a blip could restore to normal. A squeaky seal type noise was coming from the throttle body as throttle blipped. But for the record I loosened the clip on the valve body as suggested above. Also after removing the rubber inlet to the valve body (easy) I wiped out all the muck I could around the butterfly and liberally squirted the butterfly shaft which disappears through rubber seals with a SILICONE spray.

I did this at least two years ago - tickover has been perfect ever since.

Good luck

Pete
Pete Tipping

Thanks for all your suggestions.........I am back from Scotland and after a good squirt of WD40 arround the throttle body and pulling the mechanism back hard, all seems to be well.

Thanks again and i know where to find some help if needed......always interesting to read the threads on here.......think I'll be fitting the B&G expansion tank with low water sensor so that we don't suffer another HGF for such an innocent fault!!

Sid
Sid

This thread was discussed between 09/11/2005 and 11/11/2005

MG MGF Technical index

This thread is from the archive. The Live MG MGF Technical BBS is active now.