Erratic Idle RPM

[Airbusguy]

Hi, I know this subject has been aired many times before. My car is an MGF VVC SE 1.8 1st registered 25.9.2000, engine No 18K4KM18377750. It's had 2 owners, 27,400 miles, full service history and well looked after.
The erratic idle RPM started last year; typically when hot the idle speed might hang at between 1400 and 2000, although on other occasions it behaved normally. I replaced the IACV but with no effect. At its annual service (with a garage specialising in the MGF) I requested they diagnose and fix the problem. I'm not sure exactly what investigation they carried out but they did fit a s/h ECU, which apparently cured the problem.

Unfortunately within a week the erratic RPM had returned; the garage is 50 miles away and therefore I can't just pop back easily. I have tried using the standard IACV reset procedure (including disconnecting the battery for 30 mins), which always works, but within an hour or so of running the problem returns. My days of doing anything more technical myself are pretty much over now.

I live in N Gloucestershire, and wondered if anyone can recommend a specialist or mobile mechanic who could help me?

Would appreciate your views.

[Roverlike]

Did you have a chance to read this thread: https://thebrm.co.uk/index.php?threads/ ... s-2j.8831/
Try to discconect solenoids from VVC HCU unit and see if that cures the problem. If it does then replace both solenoids and that is it.

[Airbusguy]

Roverlike, thanks for the link, and no I hadn't previously seen it.
One question, the suggestion to disconnect the solenoids seems to have a rider that this (only?) applies to VVC MEMS 2J cars. How can I find out if mine is this model? I gave the engine number in my original post above if this helps.

[Airbusguy]

Roverlike, I think I can answer my own question, having just seen Dieter’s mgfcar.de site. My VIN is 522563, which apparently means the car is MEMS 2. I’m not sure if it’s a 2J, or whether they are all 2J s ? If not, is the ‘J’ significant?

[markvrs]

The VIN change point for MEMS 3 was 522572, (or 522577) yours at 522563 was only just before that and I do not believe MG Rover records or production schedules were stunningly accurate.... You should have MEMS 2J. (They were all "2J")

The visible difference between VVC on MEMS 2J and MEMS 3 is the order of plugs on VVC Controller. (Fitting plugs in wrong order can give running issues)
From Left to Right
MEMS 2J. Blue/Black/Brown
MEMS 3. Blue/Brown/Black

As Roverlike says, disconnect the VVC plugs and see what happens. Zero cost option for diagnostic. If you do not feel upto taking the engine cover off then I recommend roughluckracing.com. I use them every year.

[Roverlike]

Roverlike, I think I can answer my own question, having just seen Dieter’s mgfcar.de site. My VIN is 522563, which apparently means the car is MEMS 2. I’m not sure if it’s a 2J, or whether they are all 2J s ? If not, is the ‘J’ significant?

If you have MGF VVC engine and since it is not MEMS 3, then you have MEMS 2J. There is no other engine ECU for VVC engined cars. Either MEMSM 2J or MEMS 3.

[Kasper]

Hi Airbusguy, to be honest, this issue is far from common on F’s and TF’s. Erattic idle is not unknown to these cars, but only a small part of them are vvc’s. I had the same problem teasing me for a prolonged period. Only when visiting MGFIM Sweden in 2022, it became a very hard car to drive, with no one (being along MG Fanatics) having the solution. It took a coupleof weeks and some perseverance to trace back to this cause. One of the pleasures you meet having an older car (MGF vvc April ‘96)

[Airbusguy]

Thanks for all your responses!

I'm now hoping my VVC IS a MEMS 2, but before I start the, for me, arduous task of gaining access to the engine bay I have another question about these solenoids. I was earlier referred to thebrm.co.uk website, which has this photo, see attached BRM VVC, showing the 2 solenoids. I happened to have a photo of my own engine, see attached Rover MGF VVC, which whilst not very clear appears NOT to show a 2nd solenoid, just the blue one (click on to expand).
Could this mean my engine is earlier than MEMS 2, and therefore the procedure wouldn't work?

[Airbusguy]

markvrs, I'm not sure which plugs you're referring to. With reference to my photo, it shows a blue plug, and to its left as viewed, a brown plug connected at right angles into what I think is the "hydraulic control unit" ?

[Roverlike]

markvrs, I'm not sure which plugs you're referring to. With reference to my photo, it shows a blue plug, and to its left as viewed, a brown plug connected at right angles into what I think is the "hydraulic control unit" ?

Blue and black plugs are the ones you need to remove and see if that would resolve your problem.
You black plug is positioned above blue plug and you cannot see it clearly on your picture. MGF VVC engine have these 2 plugs positioned differently due to limited space. They are positioned one above the other and not one to the left side of the other.

[Airbusguy]

Roverlike, Thank you and sorry I hadn't realised you'd posted on both forums!

[Airbusguy]

Hi Airbusguy, to be honest, this issue is far from common on F’s and TF’s. Erattic idle is not unknown to these cars, but only a small part of them are vvc’s. I had the same problem teasing me for a prolonged period. Only when visiting MGFIM Sweden in 2022, it became a very hard car to drive, with no one (being along MG Fanatics) having the solution. It took a coupleof weeks and some perseverance to trace back to this cause. One of the pleasures you meet having an older car (MGF vvc April ‘96)

Hi Kasper, you say you had the same problem as I have, could you tell me what was the cause?


?

[Kasper]

Vvc solenoids, as I have an early vvc f, this is an issue not too many people came across. All technicians start to look at the common and known things first, replace all kind of things without cure so it ook us about 3 months to find out. Our well known, TF experienced and capable mechanics hadn’t met it before. There is always a first.