Think I've found the problem...G60 v low mpg - advice needed

[TomD 0]

Hi All! This may go on a bit as its been a while, but here's the story...

 

Some time ago I put a new decat pipe on the G60. When I did it I broke two of the wires on the lambda sensor as they'd gone very brittle with time. Blew the fuse on the fuel pump circuit etc...

 

...After some help from some of you guys, worked out what the problem was, unplugged the lambda sensor and it worked fine.

 

I was expecting the MPG to go way way down with it unplugged but it didn't really change at all - stayed around high 20's. Did seem a little richer though

 

Anyway, this was well before christmas.

 

Also, engine mounts were worn out causing the manifold/downpipe to leak. Fixed engine mounts but left leaking exhaust as was

 

Easter weekend suddenly the MPG dropped loads, stuggled to get it into the 20's. Also accompanied by big flames out of the exhaust, it used to pop a bit before but this was much more often, much louder etc. Plus it seemed much richer, smell of fuel/black smoke/soot etc

 

I thought this must be a combo of no lambda sensor and a leaking exhaust, but why did it take 4+ months to happen?

 

So I decided that it would be a good idea, as I had to fix the manifold/downpipe anyway, to buy a g-werks 4 branch :)

 

When the time came to fit the 4 branch, it turned out half the studs were snapped, rounded bolts etc, and I didn't have time to do the work, so it went off to the garage to have the head off, new studs etc.

 

When it came back, it still had very low MPG, popped occasionally but nowhere near like it had done. So I decided to get round to doing the lambda sensor. So I fitted a new one on the weekend.

 

Anyway. on the way to work this morning the car felt pretty flat, with a more noticeable flat spot/hesitation low in the revs...pretty noticable in a G as its normally really good from low down.

 

I'm sure it was running leaner, as the engine temp was running hotter and the 4 branch was getting much hotter than it has been so far without a lambda sensor. So the lambda is doing something. But it was still returning a crap MPG.

 

Anyway, before I came home I unplugged it (just in case I was doing it damage more than anything) and it was back to how it was before - Running well but a fit fuely and still bad MPG.

 

So at the minute I'm wondering...

 

a) The timing would have been set with no lambda sensor (it also had a new cambelt about 2k before the manifold was fitted)...is it possible that having one is throwing the timing off? (Thats the kind of flatness it feels like) What timing should have it been set at? 6 Degress BTDC? Would it effect it at all?

 

Could explain the crap MPG/running hot/flat spot?

 

b) Is there something (i.e. in the ECU) that needs to be reset now its got a working lambda sensor? Like has it got used to not using one?

 

I'm starting to feel a bit lost on this one now, it needs to go in to the garage for a new front wheel bearing during the week so I think I might ask them to set up the timing again with it plugged in?

 

Please help if you can...she's looking sweet now she's got the RS's on for summer but I really want to get her running right....plus the petrol's killing me!

 

Thanks in advance!

Tom

[Riley 0]

Id have it set up again now the lambda is plugged in and sorted.

The g60 ecu dosn't need resetting.

 

Neil.

[TomD 0]

Ok, its going in thrusday to have the wheel bearing done, so I'll ask them to plug it in and check the timing.

 

Any other ideas guys? :)

[DanVW 0]

When you get the garage ask them if they have an exhaust sniffer then get them to check the timing and ask them to set the co at the same time as below:

 

1. Let the car run and warm up. Oil temp has to be at least 80*c, best if the rad fan has cycled at least twice.

 

2. Rev your motor past 3000rpm three times for at least one second each time. This lets your ECU get out of warm-up/coldstart mode.

 

3. Unplug your blue coolant temp sensor, on the main radiator hose in front of the head. The ECU is now in diagnostic/tuning mode, and it will save new values inputted to it as a new baseline of initial settings.

 

4. Set timing to 6*BTDC. Advancing or retarding it from there does nothing but screw up how the car runs, this is the baseline from which the ECU will advance or retard timing electronically.

 

5. Monitor the CO % level from the sniffer pipe upwind of the catalytic convertor. Adjust the CO pot so that the CO level is 0.07%, +/- 0.05%, with the HC levels below 120ppm.

 

6. Adjust the idle screw according to your cam. Stock cam = 850rpm, 260 cam = 950rpm, 268cam = 1050 rpm. This can be +/- 50rpm.

 

7. Plug the blue temp sensor back in. The ECU has now saved your values, the car is properly tuned, and you can go play.

 

(Above taken from the Bently bible :-)

[peteTDI 0]

When you get the garage ask them if they have an exhaust sniffer then get them to check the timing and ask them to set the co at the same time as below:

 

1. Let the car run and warm up. Oil temp has to be at least 80*c, best if the rad fan has cycled at least twice.

 

2. Rev your motor past 3000rpm three times for at least one second each time. This lets your ECU get out of warm-up/coldstart mode.

 

3. Unplug your blue coolant temp sensor, on the main radiator hose in front of the head. The ECU is now in diagnostic/tuning mode, and it will save new values inputted to it as a new baseline of initial settings.

 

4. Set timing to 6*BTDC. Advancing or retarding it from there does nothing but screw up how the car runs, this is the baseline from which the ECU will advance or retard timing electronically.

 

5. Monitor the CO % level from the sniffer pipe upwind of the catalytic convertor. Adjust the CO pot so that the CO level is 0.07%, +/- 0.05%, with the HC levels below 120ppm.

 

6. Adjust the idle screw according to your cam. Stock cam = 850rpm, 260 cam = 950rpm, 268cam = 1050 rpm. This can be +/- 50rpm.

 

7. Plug the blue temp sensor back in. The ECU has now saved your values, the car is properly tuned, and you can go play.

 

(Above taken from the Bently bible :-)

 

 

it's been posted on here before that you set the timing holding the rev's at round 2.5 to 3k ,is this not the case?

 

on the CO settings is this done at idel and if the cat's not fitted are the setting the same?

[DanVW 0]

You do (for some reason) have to set the timing while holding the revs at

2-2500K (any more and your using boost!)

 

But the above guide is for checking and adjusting the CO pot, not the timing!

 

As for not having a cat then @ step 5. Monitor the CO % level from the sniffer pipe upwind of the catalytic convertor. Adjust the CO pot so that the CO level is 0.07%, +/- 0.05%, with the HC levels below 120ppm.

 

You can put the sniffer pipe up the tailpipe rather than upwind of the Cat.

[TomD 0]

Thanks guys - i'll get them to check that out!

 

fingers crossed! :)

[TomD 0]

Ok...

 

Car came back from the garage on thursday. I plugged the lambda back in before it went, and the timing was fine, and the CO pot measurement was fine.

 

but its still doing the same thing.

 

So I re-earthed the Lambda sensor to make sure it was earthing properly...no change.

 

The only way I can describe it is its taking too long to move from closed loop when cruising to open loop when opening the throttle.

 

Like you press the pedal down anf normally it takes off pretty much straight away, but with the lambda plugged in its flat...flat...flat...then picks up eventually. But if you've been giving it stick, come off the throttle quickly, and then back on it, its fine. (i.e. I'm guessing hasn't gone back into closed loop??)

 

Also, doesn't seem to do it when its cold (i.e. does the car not go into closed loop mode until its warmed up??)

 

I'm beginning to think the low MPG is a seperate issue now.

 

Anyway it makes the car a pain in the arse to drive, and nowhere near as fun, so its unplugged again! :(

 

Thinking maybe its a crap lambda too?

[Rob Heath 0]

Genuine or non gen probe??

 

Maybe worth gettin a genuine one

[shawshankkid 1]

Agree, get a genuine one and then see how you go, any probs within the 2 year warranty and you get a new one free.

[TomD 0]

Its not a genuine one. :oops: :oops: :oops: :oops:

 

I know I know.....I was having a very very expensive couple of months due to the rest of the work above, and found a Febi one that was the right one for £60, rather than £120 odd quid.

 

Any chance I can get a refund from AVS (where I got it from) as its not working properly?? Unlikely I guess but still.

 

I thought lambda's (of this type anyway) were all generic anyway, and it was just the wiring/plug that changed?

[G60 Bob 0]

It could be the blue temperature sensor; it makes the car use fuel and pick up slowly. Just swap it with the black one beside it on the water flange at the front of the engine and see if it improves (you'll probably notice the water temp guage not reading properly if the blue sensor is knackered)

[TomD 0]

Ok....more info on this....

 

I found the Pit stop Developments G60 Diagnostic article which was useful....

 

http://www.pitstopdevelopments.com/guid ... gement.pdf

 

...so borrowed a multimeter and off I went...

 

Point 1) My voltage levels were below what the guide said, so i traced the wire from the alternator to the bat...found part of the insulation had rubbed away, so taped it all up, wire brushed all the connections and put it all back together. I'm getting a much better voltage now, so fingers crossed the alternator's not knackered.

 

But it still managed 18mpg! ARgh.

 

So onto Point 2) I checked the impendence of the CO pot .... guide says 500-600ohms....mine was reading 89!!

 

So turned the screw a few times and set it at 550 ish.

 

What would having the CO pot set to a very low resistance mean for fuel economy and engine runnning/performance?

 

I can't take the car out to see how it feels at the minute.

 

Cheers! :)

[TomD 0]

Ok...having said that the voltage being produced is ok...

 

I'm 99% sure I've found the problem...

 

When I tested the voltage after firing it up from cold it was above the 12.8v that the PSD guide says the ECU needs. My headunit (for some reason) has a voltage meter built into it, so I checked the readings compared to the mulitmeter, seemed pretty accurate.

 

So...started car, voltage was over 13 volts. Set off, first few minutes, drove sensibly, and the volts stayed over 13. The car returned a sensible mpg too (about 25...not bad for when its cold) But then went onto dual carriage way, and as engine speed/load increased the voltage decreased, staying consistlently under the 12.8v (around 12.3-5 ish) As it did this I reset the mpg...started doing about 17-18 mpg. (This is only with sidelights and stereo on) As in the ECU hasn't got enough Voltage -and has gone into limp mode.

 

So I'm guessing the alternator's had it, but what are the other causes? I'm guessing:

 

1) Dodgy wiring

2) Loose belt (though it seems ok)

 

Is there anything obvious that I need to check that would cause this?

 

Also, has anyone got a working G60 alternator for sale?? :)

 

Thanks in advance!

Tom

[g60ff 0]

Might be worth trying one of these before you start looking at a new alternator. Sorted out the low voltage issues on my G60.

 

To make sure it's the right one whip your current regulator out and check the part number, it should be in the listing.

[peteTDI 0]

try pushing and jiggling the key in the ignition barrel when the voltage drops and see it it comes back up, my g60's doing the same thing :(