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MG MGF Technical - ErraticTickover and VVC Solenoids

Here’s one for the archive.

The problem was an erratic tickover speed that varied from 900 rpm to 1500+ rpm almost at random.

this is the sequence of events in my attempts to cure the problem, led mainly by the archive with odd forays into Dieter’s site and the Elise board.

1. Check throttle cable
2. Check and clean coolant temperature sensor connections
3. Clean ECU multiplug connections with contact cleaner
4. Point to point check wiring from temperature sensor to ECU
5. Change temperature sensor
6. Remove and clean throttle body, check for sticking butterfly
7. Check throttle position sensor with ohmmeter
8. Check TPS wiring
9. Clean idle air control valve (IACV)
10. Check IACV wiring
11. Buy IACV on Ebay and replace actuator and then complete valve
12. Buy throttle body on Ebay and replace existing unit.
13. Worry about needing a new ECU
14. With an MOT due, put everything back as original and decide to get it fixed professionally

Priests of Chesham, who now sell Fords but still service MGR, put the car on their Testbook and called me to say that it needed a new coolant temperature sensor, so back to point 1.

After this did not work they found an old service bulletin that described the symptoms and pointed to VVC solenoids as the problem. Apparently if the solenoids are faulty, whatever this means, the diagnostic software sees the problem as a cold engine and increases the tickover speed.

£150 and two new solenoids later and the problem is solved.

Anyone need a coolant temperature sensor, IACV or plastic throttle body?
Brian Highe

I have been having the same problems and have done most of the above and for the past few days every thing has been going well BUT when it starts again what solenoids did you replace?.
Andrew W Regens

Interesting.

I think Brian reffers to

LNN100000 - Solenoid-control valve
#26 on the EPC page for VVC
http://www.mgfcar.de/epc/2354.htm

Could anyone confirm ??

Regards
Dieter
Dieter

Hi all,
Dieter is right,this is indeed interesting;

1.This solenoid is just an ordinary coil with insulated wire to perform as a electromagnet.

2. What could disturb the fairly simple inner of this coil? Total open circuit = breakage in the windings? Partially short circuit between layer of windings (due to temperture)=too high current demand and hence MEMS switch-transistor get´s overheated after a while and goes to rest until cooled again ?

3. Would be very interesting if someone could measure with an Ohm-meter a new coil compared to a faulty one.Maybee even the "faulty" coil has to be heated to show any digression in Ohmic value? BR, Carl.
Carl Blom

Dieter is correct, those are the solenoids, called VVC solenoids by the garage, and they cost around £20 each. The mystery is that they are simply coils with two wires connected. Also, as I had no VVC related problems, they were working as intended. The problem is that when the fault, whatever it is, appears, the diagnostics in the ECU or the Testbook see it as an engine temperature related fault and not a VVC fault. Then the ECU thinking the engine is cold, speeds up the tickover.
Brian Highe

>if someone could ..... a faulty one.

Brian ? assume yours are lost ?
:(
Dieter

Dieter, after struggling for 6 months I was glad to have a fix and did not get the old solenoids back. However I did check and clean the connectors before the solenoids were changed.

As the solenoids are only two wire connection and control the VVC action, I asume that the solenoids form part of a clsed loop with cam position feedback from another sensor. If they are sticking and not moving freely then the ECU would see a fault. However, the big mystery is why the ECU sees this as a low coolant temperature.

I assume the error is in the ECU software code.
Brian Highe

At last I have had the chance to drive the car for a couple of hundred miles.

One more clue for anyone thinking they have this fault. A slight feeling of a misfire during hard acceleration has now gone away

Brian Highe

This thread was discussed between 02/10/2007 and 21/10/2007

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