Thought i'd begin a thread as i'm going to have questions...the first of which is:

 

Where can i download a .pdf of the manufacturer's schematics for a 1991 Coupe GT? I've attached a screenshot of what i have for the Porsche, i'm after this for the Polo, not a Haynes which i already have. Cheers.

Not sure if https://erwin.volkswagen.de/erwin/showHome.do goes back to the 2F but you need to sign up for free then it's I think 7 €uros for an hours use of the site where you can download all the relevant info as PDF's 

There's quite a few online parts catalogues that go a fair way towards what you're looking for. I tend to use 7zap:

 

https://volkswagen.7zap.com/en/rdw/polo+derby+vento-ind/po/

 

 

7zap looks good, thanks.

 

Also, i'm using the short transversely bolted crossmember just behind the CAT for central front end jacking, it seems to take it with a length of timber in between it and the jack to spread the load. Is this wise? Is there an alternative central point for the front? The Mk1 has the front engine mount, but the Mk2 doesn't have this and the gearbox lower mount is way off centre.

The metalwork under the cat brace is pretty strong, but the brace itself isn't, and making a hole in the cat if it slipped wouldn't be good. 

 

None of the pre-94 polos have a front engine mount, that's just Golfs. 

 

I wouldn't normally jack a car up by a central point, better to do one side at a time, even if you do need to do each lift in two stages.

 

My normal jacking points on an old polo are:

 

Antiroll bar bush mounts.

Track control arm (aka bottom arm) inners - carefully!

Front jacking points - only if you're sure they're solid.

Rear beam

Jacking points (only if they're definitely solid)

I've attached a photo of how i'm jacking, just for interest. The members on the ends are taking most of the load with the timber as a spreader bar, but yes, the brace flexes slightly. I'm going to get it reinforced when i start the head gasket change, i'll make up some pieces out of scrap and use the big spot welder at work to attach them.

 

All brakes front and rear now serviced, i'd forgotten how much of a pain that big bottom spring was on the rear shoes. Had to remove the metal plate from the front pads, (see photo) wouldn't fit with it on.

 

Couple of questions:

 

What brand should i be looking for when buying a water pump and a timing belt? Don't want rubbish.

 

It has some very minor cold running issues right after startup. Smells rich, tickover at 1500 and misses when you open the throttle. Is this pointing to anything? If i have to test every component with a multimeter one by one i can do that.

blue temp sender for the the running issues maybe, dont buy cheap ebay rubbish

 

can also unplug the o2 sensor to see if that helps

When you say the o2, is that the one by the cat?

yes

Busy easter with the 2F GT, the head gasket was leaking oil from the corner so the head is off and in bits. Now begins that familiar process of sorting everything out before the rebuild, and true to form, the non-comformances and coming thick and fast.

 

Found out what was wrong with the O2 sensor, broken wire at the inlet manifold multi plug. So much degreasing to do because of leaked oil and had to resleeve the alternator cables. Alternator is stripped down because it was full of oil, don't know if it'll work again, fingers crossed. The big win for today was getting the AOS off the block, the bottom bolt was very badly gone, i got it in the end with heat from a pencil blowtorch and by hammering a cut down TX30 into it. It washed out fine, but was full of mayo and water.

 

I've lapped the head with 120 and a length of 6mm shim steel, same with the block, the both came up great with a few witness marks left and went flat to within half the specified tolerance. The factory honing marks can still be seen on the bores, it'll make a good engine when its done.

 

Question- is there a thread on head porting and gasflowing on here?

 

 

The valves looked pretty agricultural as standard, so i've reprofiled them to Grp A standards. The technique is a bit odd and risky, but it's down to the skill of the machinist really not the size of the machine, you have to nibble bit by bit. I've only got a 16mm button cutter which is perfect for a 28mm exhaust, but a bit small for a 36mm inlet; i have to make do with what is kicking around the factory. The cam will stay standard for now.

 

All the Digifant sensors were loop tested back to the main plug today, but i got some odd readings off the barn door MAF. Does anyone know what i should be seeing for the MAF? It starts at about 600ohms and rises to about 1.3k before dropping back to 600 at full deflection...doesn't seem right to me. Anyone know?

This is from Autodata

Thanks, i'll retest tonight. My initial test was done from the Digifant plug, but looking at the schematics wiring is shared with other potentiometric devices which could cause problems. I'll do another test from the barn door terminals.

 

Interesting how they call it a VAF, when actually it's a MAF. Perhaps this is to acknowledge the fact that the mass calculation is actually performed elsewhere.

The MAF is stuffed, it needs a new board. Anyone know where i can send it for repair?

31 minutes ago, mr brightside said:

The MAF is stuffed, it needs a new board. Anyone know where i can send it for repair?

Have you popped the plastic cover off and sprayed the wipers with some electrical contact cleaner (NOT WD40 !!) 

11 hours ago, nige8021 said:

Have you popped the plastic cover off and sprayed the wipers with some electrical contact cleaner (NOT WD40 !!) 

Yes, i've cleaned it, i've drilled the board mounting holes out so it can be repositioned, i've bent the wiper slightly so it presses on more. It's annoying because the 924S has done 170k on the same AFM and it works fine, the Polo is on 82k and a goosed unit.

 

Anyone know where i can get it serviced? You can get chinese copy boards off Alibaba from Hong Kong, but i'd rather have a Bosch board and have it fully calibrated. Proper job, basically.

Update on the AFM, a company called ATC Drivetrain have rebuilt it for me for the outlandish sum of £360 inc. I'm having difficulty extracting information from them pertaining to what i've got for my money, the invoice just says 'rebuild'. I'd like to know what parts were used and whether they were genuine Bosch, and also whether it has been calibrated, but they've gone all quiet on me. If it's still got the old board in it and they've just dicked about with it a bit i'll be a bit upset.

 

The engine is back together with the head ported a bit and quite well gasflowed. The ports were pretty well gasket matched and i just enlarged them a bit, but the valve chambers needed quite a bit of work. There are numerous obstructions, all fairly obvious and all with the core on the other side of them, so you have to smooth them out rather than removing them. I find using teaspoons of various sizes handy for this task; it allows you to match the other 3 nicely when you're happy with the first one. I left the guides on, just chamfered the leading edges. All in all it took 4 days.

 

I've had the lads at work weld a strengthening piece onto the crossbrace under the cat. It will now happily take the weight of the car.

 

I haven't started it yet, it's making oil pressure and i can see oil exiting the cam bearing caps with the rocker cover off.Bit more messing about to do yet.

could have got an aftermarket ecu for what you paid for the refurb....i dont run a afm anymore

On 16/05/2022 at 20:52, steveo3002 said:

could have got an aftermarket ecu for what you paid for the refurb....i dont run a afm anymore

Problem is i don't know where to look, where can you get a plug and play retrofit kit off the shelf?

 

I was thinking that when all the correct sensors are purchased (MAP, TPS, blue temp) that would take it over the price of an AFM refurb. Plus there's a session on the rollers after that to trim the basic starter mapping.

company called kdata was doing plug n play but a bit pricey

 

look at microsquirt or speeduino , as you dont really need plug and play that way you can use alternate sensors etc and make a new engine loom  

 

when i got mine i paid £300 for a ready made microsquirt and diy loom 

Edited 20 May, 20224 yr by steveo3002

Advice needed.

 

First startup today, it sprung into life with no fuss at all, but the idle is rather unstable. If you unplug the o2 sensor there is no change in engine speed or running quality at all. There are no big leaks coming from the evaporative loss control system, but that odd vacuum temperature switch on the induction is passing slightly and bleeding into the throttle body. The vacuum hoses associated with the air flap in the airbox scoop are also ok.

 

If you give it a few revs the idle speed stays up high for a lot longer than expected, and if you open the throttle too fast it hesitates quite a bit and sounds like it's going very lean. I've ordered a new o2 sensor. Any thoughts?

id blame the afm 

 

should run almost perfect with the o2 undone , its not that 

 

i did alot of fault finding on mine before i went for a new ecu

The resistance readings from it are a lot better than they were, and as far as i can tell within spec. I'm going to persist a bit, as the repair included a full calibration on a flow rig.

 

How do you reset the digifant fault codes? There's info online, but it's all incomplete and every time i find a link it's broken. One method has to do with the blue temp plug, and another relates to the diagnostic sockets...can anyone expand?

 

Also i've found reference to a home made code reader, but again the link to the drawing for the wiring is dead. A lot of pages refer to you having to reset the digifant after an AFM change. Does this link look any good?

http://eva2.homeip.net/eva2/FU01/ch8.2.html

you can use  cheap code reader or get a lead and copy of vcds from ebay or the like

20 hours ago, steveo3002 said:

you can use  cheap code reader or get a lead and copy of vcds from ebay or the like

 

Have you got a link to any of these things please? The only set of diagnostic leads i could find were listed by some joker from CZ who wanted £80 postage. I have seen a lot of cables for sale, but they're all OBD2, and digifant 1 is OBD1. The one i want is a simple piece of apparatus- 3 wires, an LED and a switch, people have made it up themselves in the past but all the links are broken and the pictures irretreivable from the host server.

 

I've got much better compression than when i started, but the plugs are looking rich and it has unburnt fuel going through the exhaust. The timing mark is jumping all over on the strobe and it runs lumpy at idle, thing is i don't know what's causing what with those two symptoms. I may have to change the distrubutor for a new one just to rule it out, there's no other way to be sure.