3b misfire, G40 code

[Tony Stark]

Ok, my 3B has had this full throttle misfire for ages now and its starting to chap my ****. Its only behaved properly once during a day out since ive had it. Usually this intermittent flutter/miss is there.
Its had Cap, rotor, plugs, timing belt, mark h mod no other leaks, maf connection carefully checked and cleaned, tried another used coil, and isv as the old one was scored inside. Temp sender on the back of the head appears to do its stuff ok.

I havn't replaced the ht leads yet its next on my growing list of to do's.

Plugged in with solus pro yesterday morning.
Camshaft position (hall) sensor *
(g40) open circuit/short with power intermittent.

Could a faulty hall sensor give these symptoms? Would it not just be start or non start?
Only ever had one non start - yesterday afternoon after checking bits, Third attempt it fired up. Not sure what id done. Still misses under heavy load fine otherwise.*



Any advice muchly appreciated, as its spoiling all the fun

Thanks.

[UrS4boy]

7A, 3B and Early AAN G40 Hall sender replacement DIY

*If* you need to replace the Hall sender and the dealer doesn't have one available at decent price, you might want to consider a DIY, following the procedure shown in this pdf:

http://12v.org/urs/ReplacementOfTheH...istributor.pdf

[Tony Stark]

Thats a great write up there. I think im gunna replace that part regardless it'll put my mind at rest and its hardly the sort of thing you can pop out at the road side.
Thank you.

I also had a look at the water manifold temp sensors while i was checking a few things, there are two of them, a 1pin and a 2pin. i did find a 4 pin mfts sensor a while ago but it was unscrewed with cut wires on it laying on the block like someone dropped it while replacing it and then realised its tighter than a gnats vaj down there so left it.

The temp guage works ok, the additional coolant pump also primes with ignition on, it did have a/c but its been fully removed. So its ok like this on a 1991 3b? these have no effect on fuel/spark timing or anything, thats done by the cylinder head temp sender yar?

[UrS4boy]

The temp guage works ok, the additional coolant pump also primes with ignition on, it did have a/c but its been fully removed. So its ok like this on a 1991 3b? these have no effect on fuel/spark timing or anything, thats done by the cylinder head temp sender yar?

Not sure about a one-pin sender. The 2 pin sender is for the after-run pump.

http://forums.quattroworld.com/s4s6/msgs/21503.phtml

The F76 MFTS does interact with the 3B ECU so I think you should replace it. Some info here (and follow its internal hyperlinks):

http://forums.quattroworld.com/s4s6/msgs/22584.phtml

[prj]

Make sure the leads going to the sensor are okay. Otherwise you might buy and replace the sensor and still have exactly the same problem.

[Tony Stark]

Will do, cheers. I might do the hall sensor and dizzy oil seals anyway.

I do indeed have 3 redundant wires to the water rail and id like to have them sorted. I have a spare switch but its a 3 pin version, any idea if this will work? If not ill order a 4 pin. My other problem is the plug has been removed from the loom so dont know the correct pin/wire location. Anyone have a pic of the plug from the back fitted to a switch?

Cheers

[UrS4boy]

I do indeed have 3 redundant wires to the water rail and id like to have them sorted. I have a spare switch but its a 3 pin version, any idea if this will work? If not ill order a 4 pin. My other problem is the plug has been removed from the loom so dont know the correct pin/wire location. Anyone have a pic of the plug from the back fitted to a switch? Cheers

The later versions of the F76 Multifunction Temperature switch did away with the 12V source and are only 3 pin as a result. As for MFTS wiring, I went down my basement to look at my spare AAN harness. I found the MFTS plug boot right away but had to laugh - the wires are there but the plug is long gone (likely broke when it was removed from the engine)). So no help from me regarding wire/pin positions. You might have luck by looking at pg 52/57 of Paul Nugent's excellent ABY/ADU wiring "book" at: http://www.s2central.net/S2_Schematics/ABY_Wiring.pdf

[Tony Stark]

ok, im gunna fit a new hall sensor and shaft oil seal into my distributor.
Anybody used these guys before?

https://www.probedistributors.co.uk

As for the missing mfts, can i fit the 3 pin type sender and leave the live feed disconnected on a 3b?

Thanks for the advice so far.

[UrS4boy]

ok, im gunna fit a new hall sensor and shaft oil seal into my distributor.

If you use this 7A/3B/early AAN Hall Sender DIY:

http://12v.org/urs/ReplacementOfTheH...istributor.pdf

can you give me some feed back as to how well the DIY works (I can revise it as needed).

[LHD_Kid]

Another possibility for the misfire, what fuel are you using? (although this won't throw the fault code...)

Chris

[Tony Stark]

Another possibility for the misfire, what fuel are you using? (although this won't throw the fault code...)

Chris

Shell super, i try to get it from the same petrol station every time.

Im gunna go through everything again tomorrow morning, boost leak check, timing, wiring checks etc before fitting any new parts to the *******.

[DS2]

you didnt mention checking or replacing the spark plug leads...
mine had a bit of that same problem that under load it would misfire. it was the leads allthough not anything visible or measurable.

[Tony Stark]

I checked the resistance of the leads, all readings very similar and the insulation, they are starting to go a bit hard with age so some new'uns will be ordered.

Hope it sorts it im fed up of using the missus 3 pot ibiza. My s2 has more torque in its starter motor than that thing.

Ill do the hall sensor as per the guide and post how me and the car get on with it.

Cheers guys.

[Tony Stark]

Last weekend i replaced the hall sender and monday did HT leads on my misfiring/hesistant 3B..... with no improvement

The hall sender i received was all ready to go on a metal base plate, plastic wire retainer and correct plug so i didn't need the written guide for that part but its very good info and thanks again for that UrS4boy.



Like most things in the S2 engine bay its a bit tight for access. Heres a bit of a write up for any noobs needing to remove their 3B distributor.


First of all i disconnected the battery and removed it completely to give more room plus it should delete any fault codes while its out.

Then turn the engine over via the alternator using a 24mm spanner, removing the spark plugs makes this easier. Or rock the car forward in gear to rotate the engine.
Watch for the timing mark on the flywheel which can be seen through the gearbox bell housing inspection hole which is the same side as the distributor, with the distributor cap unclipped the mark on the shutter disc needs to be aligned with the mark on the dizzy body.


Once all was good timing wise i put a strip of tape over the spark plug holes and the flywheel timing inspection hole just incase i dropped something in their while working.

Also with the plug leads pulled from the engine it means you can pull the dizzy cap out further and out of the way.

Mine still had the tamperproof bolt and cover over the dizzy clamp, this is only a short bolt with a shallow head so its not too hard to get moving.

Ground the tip of this roll head pry bar to a chisel type end and a few smacks with a hammer and the bolt was moving.




With that out the way you can get to the 13mm nut holding the dizzy clamp.

Mark the distributor to cylinder head position clearly before you slacken it.

To loosen it i used this



Gave it a sharp smack from above with my hammer and long chisel on the bend of it and the nut was loose being careful the fuel fittings.



ground out the pin shaft gear on and stripped it to replace the hall sender. Fitted a new roll/spring pin to the drive gear on reassembly and made sure it was holding the gear tight to the shaft. Wish id replaced the gear while i was there as mine is the plastic one i dont know if the gear must on in the same orientation as it was found but i mark it anway.

While i was working on that side i replaced the FPR vac line and checked the oil breather pipes - all of which, appear to be shagged.
The company i got the parts from were very helpful www.ignitioncarparts.co.uk scuse the crap pics i used me piephone.



Anyways, it does start properly all the time now but its still the same otherwise. im guessing vagcom is the way forward to make sure things are doing what they should be?

[UrS4boy]

...The hall sender i received was all ready to go on a metal base plate, plastic wire retainer and correct plug so i didn't need the written guide for that part but its very good info and thanks again for that UrS4boy.

The DIY that I did was intended for situations where you want to use the 10 GBP Hall sender from BB AutoMacao.

Did the one that you installed look like the first or the second photo:

This?


or this?