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MG MGF Technical - Sensors, @ Will, Tony, Carl ...

Hi,

couldn't sleep and did some more useful.

You know, I'm still after the damn idle problem with my MGF and thought on having some measures this weekend.
Pulled the wiring diagrams out and put the important parts together for a better overview.

See my current know-how of wired parts and *known* voltages, resistances.
http://www.mgfcar.de/sensor/sensors.jpg
I hope it's correct. (under construction, though)

taken from MPI wiring
http://www.mgfcar.de/schedules/sb8.jpg
http://www.mgfcar.de/schedules/sb9.jpg

For myself, I didn't realise before that all the resistors are connected to a nearly independent 5V circuit and with earth to the ECU directly.

Hmm, I wonder what I can find then.
"nightingale I hear you knocking", I'll have a near look to the earth connections.

Comments ?

Back online on sunday. Main investigation will be done to the TPS again.

Regards
Dieter
Dieter K.

Err, if I only had more time for investigations.

I'm soory, did no measures :(
But I had a short near look to the ECU Multi-connector before we started. I can't get the theory of bad connection with any spade connector out of my mind.

What should I say. After start the idle just went up to 2000 rev's. I shut off the engine, fiddled at the thin wires far below at the ECU connector.
Pushed/pulled/rattled at some of the lower thin sensor wires and started the engine.
Doohh !!! Idle on 1200 revs, going down to the usual 800 after a short time. Then a 300km ride to visit my sons, with no high idle problem.

I think, I'm on the right way now with bad connection of sensor earth (pin 37+71) at the ECU or any of the individual wires (TPS may be) ;)
The wires go in very short between loom and connector. May be they go bad due to any outer side force to the spade connectors from.
http://www.mgfcar.de/power_delay_by_carl/cw_powerdelay2.jpg
(pic is not from my car, but shows the location)

No plans for next weekends but getting rid of that crap problem.
Let's see.

Cheers
Dieter

Dieter K.

Best of luck Dieter!
:-)
Hanah Kim

Hopefully you're nearly there Dieter...
Rob Bell

Hi Dieter,
I think you are probably close to the problem ! Isnīt it so that many of the electrical problems that haunt the "F" is just malfunction of the interconnections..
It is said in the manual that every connector is treated with some kind of stuff that will ensure good contact over time. Just wonder if this was deleted early by the beancounters ;o) So IMO it is important to on a regulare basis (once a year ?) treat all known connecting blocks with PROPER type of electrical contact cleaner / lubricator. And by proper I DONT mean CR5-56, WD40 and similar products.
Nothing bad about them - they have 1001 different roles in homes and cars BUT they are no good when it comes to connectors etc. Only spray-cans with stated contact cleaning / lubricating will do as Electro-lube etc. Maplin , Farnell and other sources in UK will be the place to buy these. Or you can even get some from your friendly radio/TV-shop technican.
BR, Carl
Carl Blom

Fantastic Dieter, it's always the obvious we overlook!
Will Munns

Thanks for your comments.

It's an MG and Sir LUCAS grew so old, I think he only knows of playing the simple interconnection gremlin.
It's an MG and nearly everything _is_ quite simple ;) .... OK, it should be .... ;)

May be I'm on the right way, I don't know.
Engineers never give in !!!

@Carl,
not sure about all this chemical stuff. I'd prefer clear physicals.

- Contact base material, might be any brass material.
- Spring force, a case of coincidence depending on tolerances regarding measures and male/female contact statics and dynamics...
- Contact surface.. Err... that's a poor process of getting tin or Pb/Sn on the base material. I had worst experiance with it along my professional jobs.
Thickness almost undefined 'anything'. Quality a case of coincidence.
- electro-chemical load due to surface differences, applied load and ambient conditions.

And then... put such male and female together and pray !!!

Dooh, it's better to crimp or weld them !!! :)))

Anyway, there have been several undefined dealer repairs (cause of no clear Testbook Statements)
- ECU change
- coolant sensor change
- change of the whole wiring loom
- TPS change
- throttle body change (including TPS)

I think half of them might have been interconnection troubles only ?

We should try finding strategies to analyse such mad interconnection gremlins and that's why I ask for your help.

Cheers
Dieter
Dieter K.

Getting fed up !!

Today in the late afternoon I wanted to have further investigations to finally eliminate the problem and to have some voltage measure etc..)
After a ride to the car wash I parked the MGF in front of the garage at home, boot lid up, grill remove and had a first look. Why do the wires lead _taugh_ strained to the ECU plug.

The wiring harness comes unsecured upwards from below and divides then:
Once to the main relay, once to the ECU plug. Far down visible a loose cable strap hanging around...

I carefully pulled the whole wiring harness upwards for about one inch and had look for a hole in the bulkhead rear wall where to put the stud of the cable strap.
A hole for the cable strap is missing however. In the meantime it got dark outside.

Well well, I thought, then we fasten the stuff tomorrow.
Jumped into the car, turned the ignition key,
- all lights shining as usual, alarm buzzer beeping, also like always.
- pressed the transmitter button, buzzer goes out as usual.

Then I turned the key to start , and...... NOTHING!!! Sh****!!!! No clicking, nothing. Everything quiet.

I again out to the rear, shaked at the wiring harness, starting attempt, nothing... again out, shaken, starting attempt, nothing...
What's that ????
Briefly measured power at the brown braun-pink cable (purge valve). Nothing. Dead line.

Door closed, finished for today. Tomorrow I'll see.

Me is happy having the Fiesta for rides of importance. ;)

I now would bet xx% in the last years reported errors with starter, main relay, * throttle sticking*, Senor defects, new ECU, new wiring harness etc., etc. relate to such mad contact problems with the ECU.

Will get a long night with looking up wire ways on paper and finding LUCAS electric devil.

Regards
Dieter
Dieter K.

This is what the manual says:
...............................

The ECM harness multiplug incorporates
specially plated pins to minimise oxidation and
give improved reliability.
...............................

Dunno, whether I should laugh or cry !
:)
Dieter K.

Dieter,

Sounds as though you are not having much fun !

I agree it would be great to isolate the cause of such problems. Some else on the BBS suggested a "annual clean" of all suspect connectors, so maybe a list of any that are suspect would be good idea.

The problem with tracing such intermittent faults, especially in wiring, is that moving anything, connectors or looms, can temporarily 'cure' the problem, only for it to return again later. But I do agree that cleaning such connectors can only do good.

Good hunting
Tony
Tony

I see, you are with me ;)

did the connection plan this morning. (MGF mpi, none VVC, no A/C)
http://www.mgfcar.de/mems1.9/mems1.9.htm

.. and it's raining ... no DIY weather.
Very funny, indeed.
Dieter K.

I know just what you mean, Dieter. I've been trying for several weeks now to determine why my tacho is not functioning - is it the tacho itself or the signal coming out of the ECU ?

Every time I get out there, it starts to rain :-(
Maybe that's the problem ! LOL

Tony
Tony

Rain had stopped.....

I just got back from a short ride ... with the beloved MGF (on new wintertyres, though) !!! :)

In short, the failure was the loose lower (small) connector of the main relais.

I assume LUCAS is any of the guys in Longbridge factory ;)
I think the connector secure clamp never could have been on in rught manner, cause the small brackets/noitches hold em tight on the relay if put on right.

As well I found the location where the cable strap _should have been_.

The rivet had never been in the small hole RH below at the ECU bracket.
Put on everything, and it's fine now.
Nearly fine... I still worry about a little bit strange idle.

Did pix and measures and get back when the short website is ready.

Cheers
Dieter
Dieter K.

http://www.mgfcar.de/defects/start.htm
Some nice pix (IMO). I like the Sony :)
Dieter K.

This thread was discussed between 22/11/2003 and 30/11/2003

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