Do VR6 ECU's really give problems?

[boneyjakey 0]

Hi All

 

New member here and looking for help ... got a VR6, '94, 88K miles, run perfectly for last 5 years but ...

 

- suddenly (after being stuck in traffic for 30 mins) started idling at 2500 revs, but running fine at normal motorway driving speeds

- checked the engine and the oil breather valve pipe had snapped, so replaced that but made no difference

- Googled and thought the coolant temp sensor the next likely culprit - changed it

 

Symptoms now:

 

- intermittently runs/idles/drive spot on

- starts well when cold - idles at 1500 revs for 3-4 mins and then drops to usual 750 ... after revving when warm, idle hunts a bit

- drives fine but intermittently lurches or loses power ... as though petrol mix too rich/starved of petrol

- can be hard to start when hot, and idle hunts

- possibly a bit of a petrol smell in boot?

- interestingly (?!) parked on a hill (engine at high point) and idle really struggled/lots of dying/really struggled to start

 

I'm no expert but checked for air/hose leaks; electrical connectors clean; main earth looks OK; fuses/relays firmly seated.

 

So went to local VW specialist who have diagnosed 3 engine temp faults. They say each sensor is working fine, so likely culprit is a dodgy ECU and have sent it away to be tested. I'm slightly apprehensive after searching the forum that the ecu has failed and wonder at a dodgy connection/electrical earth/fuel prob etc.

 

So, do ecu's really play up?

 

Thanks in advance

[Toad 0]

I'd look at the wiring first... Sounds more likely especially on intermittant faults.

[double-6s 0]

Welcome to the wonderful world of VR6s! One set of symptoms, four million different potential causes! :(

 

Good luck.

[Crasher 3]

The only VR6 ECU I have ever had go faulty was on an auto where the idle valve went nuts for no plausible reason. In desperation I sent the ECU for testing and they found nothing wrong until I pointed out it was just an idle control fault which they found and fixed.

[VR6 0]

My Vr wouldn't start for buggery recently - just turning over and over. Would occasionally start and for absolutely no obvious reason as to when and where it would decide that it was going to fire.

 

Swapped ECU and not had a problem since. This is, of course, before changing about a hundred other things first!!

[RS VR6 0]

Its possible that the ECU is bad...but there are at least a dozen things that can cause what you described.

 

The ECU boards are known to short.

 

I am currently having a strange issue with the check engine light. It'll intermittently come on only at idle. When I scan it...it'll say "no signal from the 02 sensor". I've already replaced the O2, the wiring, and the O2 heater relay. Since the ECU controls the O2, I'm going to open the ECU and see if there are any burn marks on the board.

[double-6s 0]

They definately go. Vince couldn't map my rado at one stage because of a fooked ecu.

[Kevin Bacon 5]

Before replacing the ECU, I'd check the following:-

 

The twistlock connector next to the electric water pump. Inspect the pins for corrosion.

 

The ECU main harness plug. Make sure the orange water seal is present and there's no corrosion on the pins.

 

Check for broken wires and shorts caused by abrasion. I had a very bizarre problem caused by 3 wires inside a section of VW plastic sheathing had rubbed together and 14 years later, they shorted. Very odd, but things like this happen.

 

Finally, remove the ECU, undo the 4 case screws, pull out the main board, take the EPROM out and reseat it again.

 

If that doesn't work and the sensors etc all check out, it can only be the ECU.

 

I have heard of ECUs going when one or more of the standard Bosch injectors gives up the ghost. Sometimes they take an injector driver out with them.