Misfiring v5 Bora

[Marshthedarsh]

Hi all. Recently picked up a 2000 Volkswagen Bora V5 for a good price, only 95,000km in the clock. 150bhp, 10v version I believe. Drove okay for a bit, but have now diagnosed a misfire on a specific cylinder - no spark from one coil in the coil pack.

Did this by pulling out the leads one by one and seeing if I still got a spark. On the pack, 4 produce a spark - 1 doesn't. This particular coil seemed to have a few cracks as well. Did some research, and signs pointed to the ignition amp. Surprise surprise, it had been re-sealed - and had been soldered inside. With the car running, did some poking inside the ignition amp around the dodgy looking wires and was able to get a spark from A on the pack (cylinder 2 I believe). So I seemed to have found the problem. However when trying to put the cover back on it must have moved the wires and haven't gotten a spark from that coil on the pack since. So I picked up a replacement amplifier, and still had the same issue. Tested the new one with a multimeter and got ohm readings you'd expect, while the old one showed a non-connection.

I have switched around the spark plugs and leads, but still no spark on Coil A (able to get one on the other 4). Therefore it seems that it is the Coil Pack that is the issue, and is not producing a spark from one coil. But I have managed to get a spark from this coil before when playing around with the ignition amp, so is the coil pack good after all? I got some epoxy and sealed up all the cracks - still nothing.

Does anyone know of a way to test whether the problem is the coil pack or amplifier, or even other? After getting a spark - the new ignition amp should have solved it. So either this amp has a fault on that cylinder control as well, or the coil pack has an intermittent fault and will fire under the correct circumstances. Therefore I need a new coil Pack?


Any help is appreciated, cheers


I should probably add a few things... When key switches the interior on, the fuel gauge needle moves to where it should be - but the engine temp gauge needle just moves to 50 (the minimum), and does not move at all when driving. Does this indicate a temperature sensor fault? Service light comes on, but overdue for one anyway. Have ordered a Vag-Com scanner, but has still not arrived. Am keen to check the codes and see what I get. Idle is a bit rough, sits around 800, but smooths out over 1500 - though this is an obvious symptom of a misfire. When I did get all 5 firing it was quite smooth. Transmission is a bit rough changing gears (Automatic), though is this just a result of the misfiring?

Currently not driving the car atm, sitting waiting and hoping for an easy fix.

[Marshthedarsh]

UPDATE.

Have worked through the coils systematically looking for sparks on the removed spark plug when only running the power source and one pin (for one cylinder) from the pack. Sounds a bit complicated, but actually quite simple.

Basically, I can get all 5 coils on the pack to spark when each is connected to one cylinder pin coming from the ignition amp into the coil pack, but only from 4 out of 5 of the cylinder pins. This seems to indicate that all 5 coils will create a spark, but the ignition amp itself won't tell one to spark when all plugged in correctly.

So it seems the replacement had the same issue as the original, hopefully the third amp will do the charm...

[Crasher]

Firstly you need to fit a new genuine VW ignition amp, VW part number 071 905 143 and good quality coil (not necessarily genuine) VW part number 071 905 106 and good ones are available from Beru, NGK and Bosch. The aftermarket amplifiers available from Standard, QH and Facet I have found to be utterly useless. They are stupid money here at around £360, I dread to think what one will cost in NZ!

[Marshthedarsh]

Hmmm, now things are really getting strange...

Got another amp, same problem. Decided to test all the coils one by one again, still all sparking. However, what we've now found is that the brown plug on the top that goes into the ignition amp - one wire won't tell any to spark (and controls the coil the misfire is on). This is the opposite to what I found the other day, so it seems that the ignition amp WAS working - and it's just not getting the signal from the ECU.

So could this be a faulty ECU? Or just a bad wire into the amp. Possibly a bad crankshaft and/or camshaft sensor... Considering I was absolutely sure all the wires were working when testing the other day...

[Crasher]

Have you done a code read yet?

[Marshthedarsh]

Not been able to do a code read yet, but trying to get one done ASAP.

I've managed to find that all 6 wires into the amp connect to the ECU, so not a bad wire. Basically I believe the ECU isn't telling one coil to spark when the car is running. Is this a simple case of needing to reset the ECU so it can relearn itself? Or is this a symptom of a bad ECU, and I'll need to swap it out for another...

[Crasher]

If it is the ECU, you cannot just "swap it out" as it is coded to the instruments and a used or new replacement cannot be easily coded in, we usually have to take the car to the VW dealer.

[Marshthedarsh]

New ignition amp, same deal. New coil pack, same deal. No spark on Coil A. Have tried all the permutations of spark plugs and leads - so it pretty much confirms that the amp is not receiving a signal on pin 6 (from the ECU) - and therefore not telling coil A to make a spark. Result: Misfire, only 4/5 cylinders running.

I'm just wondering if there's anything else that can cause a constant misfire like this. I haven't been able to do a full scan - but one of the few faults I got was the ECT (which I assume accounts for the Temperature Gauge on the dash not moving above the minimum of 50). Have bought a new one, and will install it when I get it. I can't seem to see a green one anywhere, so it possibly still has that Black one that always gives in. Have read that if this doesn't work it can cause a misfire, but then so can many things.

Otherwise I'll take it to the VW dealer to get the ECU looked at. From what I've read - it seems that they're able to reprogram it and it will work completely again. Is this the case?

cheers.

[Crasher]

The ECT sensor is in the water housing on the side of the head that also contains the thermostat. Yes the dealer can re-flash the map on that ECU BUT if it is a driver failure the ECU will have to be physically repaired or replaced but to be honest I have never known a coil driver to fail, ever, BUT the system on that engine is unusual even compared to the V6 version plus that amp is very prone to failure so who knows what could happen. This new amplifier, is it a brand new genuine VW dealer supplied part?

[Marshthedarsh]

When I got the car, (I think) it was firing on all 5. When it started misfiring, we opened up the (resealed) amp and a mate had a go at poking some of the wires inside. Managed to get the 5th cylinder firing when poking a dogy wire, but it dropped when we tried to put the lid back on. So at this stage it strongly seemed like the amp. He had a go at re-soldering it, but when we started it again - we saw some sparks jumping across some wires inside the amp. Turned the car off straight away, looks like the wires had been too close together. Though I can't imagine this would kill the ECU and cause it not to spark anymore.

Got a "working" replacement from a euro parts scrapyard and that didn't fix it. Either it had a similar problem, or it wasn't the amp at all.

Got a third one from a guy who knows about these parts. Refurbished in the UK with a 24 month warranty. Same problem. It's possible they all have the same issue on the same control - but I think it's highly unlikely.

It's just a huge, annoying mystery. Thought I'd solved it - but two replacement parts haven't fixed it. But then why did we manage to get all 5 firing one time :s