Lean readings on wide-band

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chrism

New Member
Ive been getting erattic afr´s/lambda readings on idle. They show almost always lean mixture. It hesitates under part load but at FOT it goes perfectly. Ive tried checking all vacuum hoses but still the same. I was at the maf yesterday and managed to loosen the wires to the plug. I ordered a new maf and pigtail but decided to solder the connection today and it was fine.

I hooked the ecutalk up to it and noticed the o2 sensor was showing 0 volts. I gave it a drive to warm it up so as to ensure the closed loop starts but it didnt register any voltage whatsoever. I take it you should see the voltage rock back and forward between 0 and 1 or 1.4 volts, or whatever it is, when on tickover?

I even unplugged the sensor completely but it behaved exactly the same. Im going to try and borrow a mates spare sensor.

Is there anything Im missing?
 
stumo

stumo

Active Member
If you are talking about the O2 sensor in the car then that is not a wide band, it's a narrow band.

You can check the continuity of the wiring back to the ECU.

Disconnect the O2 sensor, turn on the ign, there should be battery voltage between the right hand connector and earth (looking at the connector)

Switch engine off, check continuity between the left hand connector and earth.

Disconnect the battery, disconnect the ECU, disconnect the O2 sensor. Earth out the center pin on the O2 connector on the loom, put a volt meter fvrom earth to pin 19 and it should show 0 ohms, if it doesn't then check the wiring.

if that fails, rub yer ballz on anything that you can.....
 
PobodY

PobodY

Moderators
Staff member
Again, a word of warning; the lambda probe has an internal heating element. Rubbing it on sensitive skin may have undesired effects.
 
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chrism

New Member
Thanks for the help, thats appreciated but Im a bit worried yer all a bit ball-fixated over there. Dont get me wrong: I like a good ball-rub now and again but I usually keep it to myself.
 
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chrism

New Member
Ive checked the wiring to the 02 sensor and it was sound. I changed my fuel filter today and hooked up a pressure gauge to the fuel feed. It was mapped to 4 bar without vacuum. It was slightly high, nothing much, so I adjusted it.

The afr at WOT is slightly high...sometimes. This shouldnt have anything to do with the o2 sensor. Im thinking the fpr is maybe not working properly either. Still getting no signal on my ecutalk to the o2 sensor. Im gonna borrow an 02 sensor in the next couple of days ans see if the idling afr sorts itself out as well as part throttle driving. But, how can I test the fpr? I can see that the pressure drops slightly when I re-attach the vacuum hose and when I rev the engine it goes back up to the 4 bar but how do I know its following boost pressure up to 2bar(6bar total)?
 
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chrism

New Member
I think Ive found the pronlem. A problem at least. I noticed that two nuts were missing on the backside of the left-bank intake manifold. This must be letting in air.
 
stumo

stumo

Active Member
:doh:

atleast you found a problem....whether that fixes it is another matter...fingers crossed
 
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chrism

New Member
Making headway. Managed to get the remaining two nuts on the intake on today. The idle is now as good as percect Im going to get on it. Its still lean on very slight throttle but whilst driving the hesitation is much better. Still jerks a bit when Im cruising. But even after letting it warm up properly the idle is spot on.

Even dared to give it some welly on the motorway and I got a prefect afr (ie 11.76) on full boost@ 1.5bar.

It now seems theres no leaks at idle but theres still something causing the hesitation. Ive changed plugs, dizzy, rotor, o2 sensor, fuel filter, almost all vacuum lines I can get to, spark leads were new last year. Ive ordered a replacement maf from the us. Its a Q45/P60 bugger.
 
PobodY

PobodY

Moderators
Staff member
TPS?

You expect it to be lean at idle and slight throttle don't you? There's no real load on the engine so there's no point in throwing fuel at it... but if the TPS is out it might not be recognising that you're not idling any more.
 
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chrism

New Member
Ive adjusted the TPS from 0.55ish to 0.46V at idle, but I suppose it can still be faulty.

I wouldnt expect it to be lean on idle. Id expect a lambda of 1/afr14.7 Nor do I expect it to be lean on part throttle either. To get through the mot here you need a lambda of between 0.97 and 1.03 on both idle and ca. 3000 revs. It wont go through if it doesnt stay within these parameters. Obviously, the important thing is that the fuelling is fine when Im belting it but it still isnt doing exactly as it should. Ill wait and see what the new maf does for me and if its still the same Ill start scrutinising the TPS.
 
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chrism

New Member
Update: fitted new maf and the idling was actually even better but it is still slightly lean on very, very slight throttle as well as revving it up in neutral. The hesitation is much better but its not 100% yet. Im actually going to check the plugs as it feels like its that type of problem with the missing now.

I changed the fuel filter but it was just the same. Id expect it to go lean at full boost if the filter was blocked.

Ill check/clean the plugs when Ive got time and see. If it doesnt improve Ill check tps again. What was the voltage on WOT? Should I expect a linear increase as I depress the throttle?
 
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danr

Member
Q45 /P60, 90mm vs. 80mm Z32 maf.

is it a straight pipe from maf to turbo, or swan necked?
they can suffer from turbulence, ie. air fumbling back and forth over maf sensor gives flase readings, hence car bucking around. hot air blowing off fans over maf housing wont help.
get a smooth flow from maf exit to turbo as possible. no gaps in silicons joining it to pipe. chatter back up pipe from gear changes will effect it too.
mine has a swan neck frrom maf to turbo (2x opposite 45deg bends).
this may help
 
PobodY

PobodY

Moderators
Staff member
danr said:
if tps is too high (iirc) then before it gets to WOT it will think youre trying to clear the cylinders of fuel, .ie cut ignition and pump. (from memory maybe wrong etc.). http://forum.pulsar.org.au/showthread.php/67567-GTiR-tps-questions

mine is at 0.42 idle and all okay..
Click to expand...
To be honest, I think that's a bodge for having leaky throttle butterflies. - I found the opposite; if I set the TPS to be less that 0.5V at idle it really doesn't like trying to accelerate; the idle is fine, and once you get on the power it's fine, but it's the bit in between.
 
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chrism

New Member
Fuel pressure has been checked and its spot on. Im not so worried about the lean readings at idle but it wont go through the next mot if the lambda is outside 0.97-1.03.

Its the 90mm maf and Ive had near enough the same set-up for five years and it has sat perfectly on idle previously.

Pobody: my tp was at .56 so I changed it to .46 and it actually idled a bit better but it didnt affect hesitation.

However, I think Ive found the problem and I dont know why I didnt check sooner. I pulled the plugs out to see if that was the culprit for the hesitation. PLug 3 was ever so slightly lighter that the rest. Bordering on white so Im gonna stick my neck out and claim the the problem is an o-ring to the injector. Ill let you know what happens after I change them.

Thanks for the input though folks. Its good to be able to ball ideas.
 
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