VW GOLF MK3 1.6 AEE wiring loom (Marelli ECU)

[SammoVWT]

Does anybody happen to know if the wiring loom for the engine on the AEE can be bought as a spare from VW?

My wiring loom has seen better days, and the plastic coating is starting to break down and flake off. Short of replacing and re-crimping every wire in the loom I would like to get it replaced. I'm not sure if this could be an underlying engine mount issue as I get a slight idle stumble in stop start traffic which so far I have pinned down to the rocking of the engine slightly when moving off in first (only when warm of course so wire resistance is at its highest). Its enough to cause some of the wires to short out where the insulation has failed.

I've gaffer taped up the exposed wires I can see on 3 of the 4 injector connections. I've yet to strip the whole thing off and closely inspect it. I will dose it with some contact cleaner at the weekend to see if I can find any more.

I had an injector fault (number 1) short to ground recently which clued me into this little gremlin.

I assume the loom will cover everything from the coolant sensor, Map, throttle body and injector harness? When I wiggle the wires plugged into the dizzy the idle stumbles a bit too. So I think the wiring is failing at any rate. Anybody got a spare loom knocking around for cheap or able to point me to somewhere that does?

If it is VW i'll go and get one ordered. Any help is appreciated.

[SammoVWT]

Evening all,

After finally having my holiday come up i've decided to have a good look at the loom. Pulled it off today, theres not really much insulation breakdown, electrical taped it back up after giving it a good clean. Missfire was still happening after fitting today. Removed injector 1 plug and the car ran rough but the idle was stable. Removed injector 2 and the car would sometimes run more rough and then better intermittently when plugged back in. Assumed it was the loom so wiggled the injector wires to no avail, when I moved injector 2 wires the car shut off. After re-positioning the wire and restarting the car, it ran again but then got an odd idle with surges again.

Found injector 2 connector on the injector itself has become brittle and was wobbling around. I pushed it back down gently and it ended up snapping clean off (nightmare, but at least I found the problem). I hope this is what is causing my idle missfire. Its been intermittently running on 3 cylinders. It has done this for a while, but usually only lasted a few seconds - but has become progressively worse this year. I always assumed it was injector 1 with the problem since I scanned the car a few weeks ago, but it seems to be injector 2 which appears to be the real issue.

Is there a guide or procedure I need to follow for fitting a new injector? I assume I need new seals for all of them.

I know about de-pressurising by removing the fuel relay and cranking.
Disconnect battery second.
Undo injector loom from rail
Undo all injectors from the engine to be ready to remove the rail.
Remove damaged injector, fit new injector with new seals
Fit rest of injectors to to block with new seals
Re-attach rail

reconnect everything.

Is there anything I have missed? I've never done this before but it seems straight forward with the exception of the petrol of course. Can anyone give me tips on what to expect when trying to remove the injector from the rail and back into the block? Do they screw or slot in for example.

Help would be appreciated!

I am just replacing one for now, with a re-conditioned injector in the hope it will cure my problem.

[SammoVWT]

New (re-conditioned) injector ordered for next day delivery. £25.00 with all 8 new O-rings and 4 retaining clips.

To add a bit of meat to the bones, i've managed to upload some pictures incase anyone else has exhausted all ignition components, filters, cleaned out all breathers and no code. The car has always complained in the damp/cold when warm for 3 years, but it was so intermittent before it was not much of an issue. The recent cold weather must have finished the connector off through how dry it is.

Brittle Injector Connection
http://i57.tinypic.com/ic4d9s.jpg

http://i61.tinypic.com/dlt7nl.jpg

I have previously always been afraid of looking at this part of the engine, but the more I look at it the more simple and less scary it seems.

Found a nice fitting manual for anyone who has a similar issue with exploded diagrams.

Additional things I picked up:-

-Gently twist the injector to break the seal once rail is loosened in order to remove easily.
-Lubricate O-rings before inserting back into rail/inlet manifold

With any luck, tomorrow or Thursday I will be fitting my replacement injector. I will upload progress pics and update this to help someone else in future.

Injector fitting guide. Really handy and exactly what I needed.

4CV fuel injection and ignition system (http://workshop-manuals.com/volkswagen/polo-mk3/power_unit/4cv_fuel_injection_and_ignition_system/mixture_preparation_system_electronic_inj.gas/servicing_injection_system/dismantling_and_assembling_fuel_rail_with_injector s/)

PS on checking the other injectors, found that injector 1 seals have completely gone as it freely turns when attached to the rail and the block. This is clearly allowing air through as you can hear it sucking occasionally, I replaced all other vacuum lines. (Hopefully this will help cure the recent span of surging once the injector is in. Fingers crossed.

Going to replace the seals on injector 1 and injector 2 - 3 and 4 seem ok, but replace the seals going into the block as they seem very snug on the rail. Is it worth pulling those 'healthy' to refit the rail seals also? My head says if its not broke don't fix it. The only thing that is putting me off pulling all the injectors is the brittle plastic.

Since 2/3 are the hottest injectors with heat-soak I have a feeling that number 3 might suffer a similar fate and I've only ordered one injector so far to get her back up and running properly. May have to replace others shortly depending on what I find regarding the idle.
It's a bit frustrating that its taken me so long to find it - all due to no codes. The signs have been there, but they werent obvious until I had a proper look at it. I've just been fixing secondary symptoms all this time. This could also explain why my oil dirties up quickly.

The good news is now the other 3 injectors are firing with a strong pulse as I can clearly hear them, whereas I had 3 weak pulses and a half dead injector for at least a year.

[SammoVWT]

Update:

Injector fitted this morning. Was quite easy - didnt actually have to take the fuel lines off to get to this injector. De-pressurised, D/C battery and job was good.

Only advice I can give is when removing the rail, try to do it evenly and gently, dont wrench it out or you will break an injector. I used a breaker bar and some foam under the rail to gently pry the injectors out evenly, doing one side slightly then the other until lose.

Injectors came out easy from the rail with a slight twist and pull.

They did forget to send me a new retaining clip. But luckily the O-rings are in a good state, so just used a little engine oil after cleaning the injectors up and re-seated with the new o-rings. One retaining clip is cracked, but checked for leaks and theres none, and the engine is smooth. Will order a new clip as one was missing when I ordered the set. I need to do a TBA (laptop is fubar unfortunately), but it seems to be finding its limits fine and settled down nicely.

Gave it a dose of carb cleaner down the intake as I feared intake valve number 2 was a bit dirty. Sorted out any splutter at idle and seems to be fine now thankfully.

The exploded diagram is a great help and would recommend for anyone who needs to do the same.

Glad I have my wheels back with 4 cylinders instead of sometimes 4 cylinders. 30min-1 hour job on this engine. Certainly drives a lot smoother, no noticeable missfire on my drive. Seems golden now more or less all things considering. Happy bunny now - hope this is useful to someone in the future.

[SammoVWT]

Update 2:

Left the car a couple of days with injector cleaner in the tank.

Car would idle slightly better, but was quite spluttery and would stall during warmup. Very occasionally after 30 mins driving. Occasional hard starting, would take a couple more cranks than normal (could well be dirty injectors compounding this)

When starting car would start 1200rpm, which seemed high - even after the car was at 70oC. Noticed when I was driving the coolant temp needle would wobble from 90 to about 85 and back again, seemingly randomly.

After driving the car and babysitting the lumpy idle, the car gets stable(ish) after an hour and stalls out much less.

Figured now I had cured the lean condition, but the car was now too rich during start-up/running. Wasnt quite reaching operating temperature. Thought I would give the CTS a shot as when the car went into closed loop eventually it was more or less fine. Not surprising the ECU was struggling to idle before with a duff injector, 3 dirty and a busted cts.

No missfires other than at idle.

Swapped CTS this morning (blue) from VW. Fitted and car started up with a much lower idle, under 1000rpm. No code showed, and I've lost my multimeter so took a chance on it.

Warmed up quickly and idle was much more stable.

Seems to have fixed it after this myriad of creeping breakdowns, the injectors are still a little rough, but its improving after another hours drive, but the instability is becoming less frequent and not a single stall at a junction after the swap. Hopefully the ECU with now be able to re-adjust my fuel trims back to normal and some of the carbon buildup can finally dissapate. After this tank I'm dropping the oil because I used two cans of carb cleaner down the intake vacuum nozzle of the tb and the throttle body itself as I suspected it was dirty and the intake valves were dirtied up.

I have cleaned my tb numerous times over this process, and its been more or less clean every time, so I didnt remove it this time.

Fingers crossed i've gotten to the bottom of all the secondary and primary symptoms! This car is a real love hate relationship.

At least I have bundles of power back under load again which is nice -it's amazing what you get used to over time.

Now to fix my loose exhaust bracket.

[SammoVWT]

Update 3:

Car seems much improved of late. Had a slight miss at idle occasionally, seemed quite repetetive so suspected it was a timing related issue. Knew mechanically the timing was good, but suspected the distributor cap.

Its an rtx distributor (not great but it does the job) with a vemo arm and cap fitted. Have been used to my old bosch one for such a long time where everything lined up in the middle with the rotor arm and contact in the cap. Didn't realise the vemo one on this distributor was slightly out of phase with the rotor arm, luckily it has a wide tab so 'advanced' the distributor cap to attempt to get the spark to fire in alignment with the contact instead of a trailing end.

Replaced expansion tank cap as it was old and thermostat as my 'new' thermostat must have been duff out the box, but the warm weather was masking it. Was sitting at 90, then 87, then between 80 and 87 degrees as its gotten colder outside.
Seems to have done the trick as the car is now running beautifully smooth with lots of power. I feel like a tool for not looking at it closely. I just lined the clips up with the middle mark on the metal clip and assumed that was a guide mark for centre!

Cleaner seems to be doing the job too the exhaust gives a beautiful tone now - one I have missed for such a long time with this lovely Jetex system. Hopefully I can finally enjoy driving my car for a change instead of being under it for a while!