MGF VVC Emissions - totally lost!

[MGNeuro]

Hi all,

I've been trying to help out my Dad with our '96 MGF VVC which has failed its MOT on emissions. So far, we have changed:

• Lamda
• MAP sensor
• Coolant temp sensor
• Wiring harness

The emissions at the last test were as follows:

• CO, second fast idle - 5.2
• Hydrocarbon second fast idle - 3579
• CO natural idle - 4.8
• Lamda second fast idle - 0.749
• CO fast idle - 1.86

So in effect, everything failed on the second fast idle and natural idle, only the CO on the fast idle test.

Everything runs fine on the car, although smells rich at idle.

We just got hold of a Pscan, with the following errors:

• map2 low fault
• fuel temp high fault
• VIS/VVT drive fault

From what I understood, the first two errors can be ignored as the VVC doesn't have those sensors, but not sure about the VIS/VVT drive fault error.

We're completely lost, so I've attached the live data when we started the car up this morning. We've yet to warm it up and see what the values are there, but wondering if anyone can help us take a step in the right direction and see if anything seems wildly incorrect there.

https://www.dropbox.com/s/3tuuiqrobjx11 ... n.png?dl=0

https://www.dropbox.com/s/9f1shpzxzssg3 ... n.png?dl=0

https://www.dropbox.com/s/oh80l1y1lofe3 ... n.png?dl=0

https://www.dropbox.com/s/cy3fuanybpz2k ... n.png?dl=0

Thanks for any insights!

[countax]

See my posting from last year on MEMS2J emission problem. In the end it was my O2 sensor.
Nigel

[JOHNDQ]

The HC's are crazy high it doesn't have a light mis-fire does it

[xr4x4]

co2 isnt much better, whats the pass on these? 0.3 or something?

[JOHNDQ]

Yep .3 fast idle .5 idle

[Marty]

those faults if timing out slightly will cause that issue

also map sensor that's used also to calibrate fueling

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[MGNeuro]

Thanks for all the help!

No misfire anywhere, so it does point to something weird going on with the lambda.

Ok, so today we tried with a different lambda sensor and car warmed up:

• Voltage is now fluctuating around 0.3-0.4v with the car idling
• When we block the exhaust up, voltage goes right down to around 0.1v
• Revving takes the voltage up beyond 0.7-0.8
• Pscan still shows the o2 sensor bank as inactive
• Fueling is at 100%
• Every now and again, the sensor state changes to active for a split second, and fueling went down to 99.5%!

We've checked the exhaust and can't hear/feel any obvious leaks, although Dad's out there tightening everything up just to be sure.

There's also a strange, brief hissing sound just after we switch the car off. No idea!

[MGNeuro]

Another update: Dad's taken off the exhaust manifold, removed the gasket and there's an oil leak directly above the exhaust manifold. Both sides of the gasket are soaked in oil. Is it possible that it could be pulling oil into the exhaust system, causing the high HCs?

[itsonlyme]

http://www.mgfregister.org/forum/viewto ... 09#p176809

it was the hissing sound that made me look at the cat

[Drew]

What are the plugs like?

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[MGNeuro]

We've put new plugs in, but the old ones were a bit sooty.

[pscan.eu]

I have spent quite a few hours comparing error codes from the factory T4 with the ones from pscan, and the latest update 041A should give the same error codes as the factory T4. The VVC drive faults should be gone.

The error codes on a 200 BRM and an MGF VVC should now be the same as the T4.

[schrokke]

The injector timing is 3ms, which is perfect. So there is no overfueling from the ECU. Lamdasensor is on live data .49V and that is impossible with that low lamda calculation from the gastester.
I think that you have a leaking injector or the fuel pressure is to high.

[2.2-600-VTEC]

Is cam timing ok as had that with timing s tooth out.

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[ORKHIS]

Any updates on this topic?

[AdamElphick]

Check the tiny plastic pipe that goes along the rear bulkhead from the ECU to a sensor on the drivers side. It gets a wear hole in it were it rubs on the oil filler bracket. I had an F that would not pass no matter what I changed until I found a hole in this pipe and fixed it.

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[MGNeuro]

So, an update after almost a year!

After all the drama, the VVT fault was the cause of our high emissions. The timing was out slightly - Dad fixed that, MOT passed with no problems.

However, it's MOT time again and it just failed again. Ugh. We just checked the cat, and it looks totally fine. The PScan data shows nothing obvious, but if anyone has a quick guide of things to check with the live data, that would be helpful as I have totally forgotten everything I knew this time last year. The car was hot when tested, so I don't think that's the problem. The car also doesn't have the plastic pipe, so can't be that!

Fast idle - CO 5.161 (Fail, obviously, this is stupid); HC 191 (pass); Lambda 0.861 (Fail)
Second Fast idle - CO 4.174; HC 181; Lambda 0.887
Natural idle - CO 1.230