MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGF Technical - Cat sensor on 97 VVC & Bypass tube

I tried to fit the bypass tube to my mgf 97 VVC but the catalyst had some kind of sensor poking out if it "overheat sensor". It's plugged into the catalytic converter itself and has a metal braided wire coming out of it. Do you know what to do with this sensor, I think the newer models have it fitted into the exhaust nearer the engine but mine is a 1997 VVC.

What does this sensor do, can I unplug it and fit the bypass tube without any problems?

John

Japanese model sir?

They have extra wiring here which, I believe, checks the temperature of the cat and warns if it't not hot enough.

P.
Paul Nothard

Yep, sounds like a Japanese import to me too. This sensor wasn't introduced to the UK Fs until 99 ish IIRC. Dieter will be able to say for sure.

SF
Scarlet Fever

Definitely a Jap import - and definitely a temperature sensor rather than a lambda-type sensor.

Not sure what unplugging the sensor will do - depends on how the MEMS is configured to respond to the sensor readings: removing the sensor will presumably default to 'cold' (effectively, an open circuit will return 'infinite' resistance; temperature sensors usually drop their resistance with temperature, and I'm sure that the cat temp sensor will not be an exception) - so will this persuade the MEMS to assume that the engine is cold, and alter the fuelliing map to suit?

Rob Bell


From memory it's just a warning sensor/light.

Popping home at lunch. Will check.

P.
Paul Nothard

As Paul has said, I too believe it is just a warning sensor - MEMs for the jap models is the same as uk models. Removing the sensor may make the warning light stay on - if it does just take out the bulb!
Let us know how you get on.
Jason H
Jason H

Any further info much appreciated
I have a Jap 96 1.8i with the same sensor in the backend of the cat. The sensor extends into the cat in path of exhaust gas so i figured it was a lambda sensor.
Pity cos it took me 4 hours to cut/drill studs out of cat so that I could refit it instead of using the bypass that I already had. Refitting exhaust tonight so will let you know how it runs without sensor connected to MEMS
Nick

John, had catbypass on my car (Jap import) and took the plug out, and it ran fine. No problem just undo it. No warning light what so ever will come up.

Currently fitted the cat back as my exhaust (ex-Rob's) is too loud without one. Well it sounds bloody awesome (it really is), but I get tired driving around.

Hanah Kim

Nice warning light pre-wired up for any different use then.

Disconnecting the jap cat temp sensor doesn't hurt in any way.
Dieter K.

John, Dieter is correct(as normal). I refitted exhaust and left sensor disconnected on MEMS side and ran fine.
Please let me know if you feel any bhp difference when you fit bypass.
Nick

Cheers Guys for all your advice!!!!

So basically when I take the cat off should I just unplug the connector to the overhaet sensor or should I leave it in situ somewhere???
Also I found that I could easily get the nuts off one side of the cat but the other 3 (sensor side) are proving to be an absolute night mare. I've sprayed them with WD40 but no joy yet......should I get the blow torch out......or even the angle grinder???

Cheers

John
John

John, the archive if packed with threads about rusted/fused exhaust nuts. Most report extreme trouble with every option tried. I see you show as a non-member (no stigma). If you register (free and simple) you will then get access to the Archive area. When I first bought my F I found the archive extremely valuable although it depends on the subtelty of your serach criteria and, of course, thread titles and contributors spelling.

I have pasted in just one extract from the archive (thanks SF):

===========================================
This is how i did it...

(For the benefit if any sensitive people out there i will leave the swearing out!)

Jack up the rear & remove one of the wheels. Position axle stands & prepare for extreme violence!

You will need...

4 sockets of progressivly smaller sizes
1 3' extension piece for your socket set
1 2' long torque wrench
1 "lump" hammer
1 set of Mike Satur KatKit nuts

20 gallons of WD 40
£500.00 UKP for the swear jar!
2 Saturday's
& an understanding partner!

The only other alternative i could think of was to drop the entire exhaust system, drill out the offending threaded rods & replace them with SS ones.

A "nut-cracker" didn't work on my car, neither did heating them up or an air line powered hack saw
===========================================
JohnP

This thread was discussed between 17/03/2003 and 18/03/2003

MG MGF Technical index

This thread is from the archives. Join the live MG MGF Technical BBS now