Another VR6 running problem (suspected Lambda)?

[SamG40 0]

Hello all,

 

Another dodgy running VR6. Up until Friday this car was running perfectly. I drove for 15 minutes to pick the missus up after work, stopped for about 20 minutes and when she turned up started the car. It was idling like it was about to run out of petrol, idling under 500 revs and flucuating about. I reved it a bit and it seemed to clear, drove home fine. Saturday morning I drove to my council lock up five minutes away and stopped and started the car and it did the dodgy revs thing again. I revved it and it went fine again. Since this point it has done it a few times but I have also noticed that the MPG is shocking, suddenly it is down to about 13-15 mpg on the way to work.

 

I unplugged the MAF yesterday when the car was running (idling fine) and it ran even worse than the times it has misbehaved. I've cleaned the MAF with circuit board contact cleaner as suggested on here anyway.

 

I've had VAGCOM on it all day today and had a couple of errors about the Lambda 00525, and 00537. They are both errors about it being out of its range which when I montiored the measuring blocks it was reading mostly at 1.203 CO especially on idle. It will never drop down below 1 (I've had the missus on monitoring duties). I replaced the Lambda (albeit with a non Bosch one from GSF) in October/November, but I'm not ruling it out. What I am wondering is, could the lambda acutally be working ok but something else is screwing the O2 up so much that the lambda cant compensate the values back down to what it should be and thats why I'm getting the lambda out of value range error codes, or is it simply a case of a screwed Lambda?

 

I ran the car down to where I pick the missus up after work and the car ran the same and with similar mpg. I also noticed as I plugged the lambda back in that someone has cut the lambda loom at some point and it has connectors joining it back up, so my first thing is to check those later on when the engine has cooled somewhat.

 

I'm really hoping to get this sorted quickly as I was planning on driving it to the Isle of Skye on Saturday for the start of a week long drive around the highlands! Sorry for the essay but tried to pre empt any questions people may ask.

 

Oh and I changed the cam sensor late last year too. The car has recently been serviced including new plugs but the HT leads do look quite old!

 

Cheers all.

[swiftkid 1]

Is it struggling accelerating? any excessive white smoke? Im asking because i've just had/am having major problems with mine, used £25 worth of fuel in about 10 miles lol. It was chucking fuel out like it was going out of fashion. have a good sniff in the engine bay see if you can smell petrol, it may be an injector stuck open. or in my case it was the ecu but thats a bit more expensive to just try out.

[SamG40 0]

No when you accelerate it seems to clear itself (although not immediately sometimes), it doesn’t seem as smooth though. It does smell of petrol but it seems to be in a limp home mode as its doing around 17mpg. I did check the wiring and where I thought I had the join in the loom it appears I have but it is a proper soldered connection that is heatshrink wrapped so I’m sure that will be fine. Having VAGCOM on it some more on warm up the lambda appears to operate normally for a time, then stays static on 1 co and then goes up to the 1.203 CO value. I’m pretty sure my issue is the lambda so I’m going to give GSF a ring and see if they will swap it.

[swiftkid 1]

Sounds very much like an injector stuck open, when you accelerate it staggars because its getting too much fuel then once you get to higher up the revs its getting near the usual amount of fuel so its runs better but because its constantly injecting your getting crap mpg.

 

does it feel like its running on 5 on tickover?

[SamG40 0]

When it is ideling fine it does sort of ‘pulse’ every so often, like I said it doesn’t seem smooth. When it is running crap its just like the MAF has been disconnected if you’ve ever done that. Hard to say whether it is running on five or not.

 

Is it possible the lambda values are a red herring then? It has happened all of a sudden. One minute it was driving fine with good (well ok for a VR) economy, the next its running rubbish. I might see about getting my injectors cleaned next week.

[swiftkid 1]

Im not saying the lambda is red herring because i've owned my VR for about 6 months now and im still learning but it sounds EXACTLY like what mine is currently doing. Mine is (i hope) just a knackered ECU, for some reasons its consantly firing on one injector, the exhaust looks like its pulsing and causing white smoke to pulse out the exhaust.

 

If you have a bit of time and are mechanically minded take the inlet off then take a look at the inlet that is connected to the head, see if one is particularly clean then put the key in the ignition position and see if any are firing. you should be able to see down the lobe

[SamG40 0]

Well just a quick update on this. Got GSF to supply me with a bosch lambda. Got it fitted and did over 1200 miles going to the Isle of Skye and back last week. Averaged over 30mpg over the whole trip and the car behaved perfectly. They have the old lambda back now and are sending it off to be tested and if its proved faulty I’ll get a refund. They were bob on about it too but still a pita in the first place. I was never happy with it from day one I wish I’d insisted on a bosch one in the first place.

[Kevin Bacon 5]

Another lesson learned (the hard way) for not using genuine parts :D

 

The lambda only operates at part throttle and idle (after the warmup map turns off). When you go full throttle it switches off, so that would be a first clue to the lambda not working. A definitive test would be to put a voltmeter across the lambda signal wire and chassis ground. After 2 minutes, the voltage should constantly fluctuate from 0.1 to 0.8V. If it's stuck at 0.5v, it's dead. VAG-COM can't keep up with the voltage change, so not worth using that tbh.

 

When you say 1 to 1.2 CO, I didn't know VAG com could measure CO! It's perhaps fudging it based on the O2 signals, or it could mean 'lambda 1', which is 14.7 Air fuel and therefore correct at idle and part throttle?. Lambda 1.2 would be very, very lean.

 

Anyway, glad it's sorted now and yep, that would have explained your horrendous mpg!

[SamG40 0]

Yep I did say when I bought the original lambda at GSF I wanted a bosch one and he said they sell loads with no issues. TBH I was in a rush for it for an MOT so just bit the bullet. Bloody pain though.

 

The value in VAGCOM was a CO level that normally reads between 0.8 - 1.1ish. It was stuck firmly on 1.203. I am assuming a value of 1 is 14.7 air fuel as when the engine is in overun and the injectors are off it stays on 1.

 

Anyway glad its sorted and hopefully this thread will be of use to someone in the future if they are having similar problems, if only they were all as easy to sort.