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MG MGF Technical - Engine problems! ran out of mechanics in my city

Hi everyone!
my vvc (1997) is running lumpy, rich, idles at 1100 rpm(warm) and at ~1500 (cold start). The power is weak until hits ~2800, from then-on seems to be as should all the way to 7000+. Each time starting engine there's about 2 seconds untill something kicks in and makes the revs go up by about 200rpm. And usually needs stepping on the gas to start up.
Tryed everything that i could think of:
*new coils(both)
*new leads
*plugs are >1000 mls old(cleanded)
*revired engine loom
*changed the purge can
*2 TB's and 3 TPS's(reset many times)
*crank shaft sensor
*MAP sensor 1year old
*cleaned the camshaft sensor
*changed O2 sensor(twice)
*spent many months rooting through the archive here looking for ideas...so finally decided to ask directly for YOUR help...please...
last time took to the dealer they said possibly TB + TPS after half an hour revving the engine, since by then i had 3 TPS's changed, didn't think 4th time was gonna do any good...
looking forward for your thoughts...
cheers!
D.G. Grand

Is the dealer doing the work using TestBook to interrogate the ECU? If so, is there a fault code being generated?

The faster than usual idle & richness points to the ECU either not getting a good input from the coolant temperature sensor (the brown one of the pair) or failing to respond to it. It would be a perfect world if ECUs either worked 100% or not at all, which is what you'd expect of solid state circuitry, however that sadly isn't the case... When the engine has been started & is idling fast, does pulling the connector off the brown sensor cause any change?
bandit

thanx for reply bandit!
sorry forgot to mention that the coolant sensor is brand new aswell...and i did try disconecting it, but nothing changed... what puzzles me most of all if where the hesitation coming from at low revs... i just bought another cranksaft sensor just in case the ones i've tried were both gone... i should probably mention that it has a home made inducion kit and a side vent scoops...but that hardly matters...
p.s. after spending so much time, don't want to give up on it..you can see the it on youtube (search) MGF VVC customized one of kind
D.G. Grand

Hesitation could be due to the over-fuelling perhaps. If disconnecting the brown sensor makes no difference to the behaviour, then almost certainly the feed from it is not getting where it should. I think in the archives you'll find a test procedure to check the output of the sensor, but if it's new then I'd suspect either the wiring or the ECU itself. Or was that part of the re-wiring?

I agree completely - having got this far, there can't be many possibilities left so persistence will undoubtedly prevail ;o)
bandit

Is the VVC mech stuck in high-rpm mode?

A
Anthony Cutler

Smiler question to Anthony... Have you checked that the cambelt is in the correct position?

The odd behavior could be that the belt has slipped a tooth
Will Munns

thanx guys!
how do you check VVC mech state? and how do you check that the cambelt is in te correct position?
cheers!
D.G. Grand

I had a similar problem a couple of years ago with a VVC. After changing a load of parts, temp sensor, throttle body etc. etc. I took it to my local ex MG dealer.

Testbook said the temp sensor was at fault so this was changed (again) with no joy. Then the lovely people checked through the old technical bulletins and found that faulty VVC solenoids can cause problems which appear, to the diagnostics as a faulty temp sensor.

£19 for new VVC solenoids cured the problem.

So here's something else to try. I think that the change can be done at DIY level.
Brian Highe

Testbook interprets VVC solenoid failure as a coolant sensor issue..? Bizarre 8-/

At £19 it's certainly worth a punt, and would be more likely IMHO than the cambelt having jumped. Let's hope that solves it finally ;o) Cambelt timing can be checked by removing the cover, setting the notch on the crank pulley to the 0 mark, and the two marks on the cam sprockets should be facing each other.
bandit

This thread was discussed between 06/03/2009 and 28/03/2009

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