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Discussion Starter #1
Just about to take my lambdas out to check them, approached car with socket set in hand and then realised - b0ll0x - there's a bl00dy big wire coming out the back of the sensor so I can't use my socket on it :( There's also naff all room for a spanner, so how the heck do you remove them in situ??
 

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With a stubby spanner. Ones easy and ones a real pooh bag.

Good luck, you'll need it. Ha Ha ha...

Do you run a PFC?
 

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Well turn the silly things off. You don't need them. Saves a load of hastle, broken skin and hours wearing the skyline scowl:mad:
 

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Or buy a lambda sensor socket - basically a deep socket with a slot up the side for the wire. Saved me a few skinned knuckles over the years.
 

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Discussion Starter #7 (Edited)
I've tried turning the O2 feedback off on the PFC and it makes no difference. Both sensors read around 1v at cold start then after a minute or so the voltage on sensor 1 (cyl 1, 2 & 3) begins to drop off. Sensor 2 stays around 1v but number 1 drops to around 0.1 or maybe even as low as 0.04v. Then the idle rpm rises up to around 1,370 and the number 1 O2 sensor voltage rises again, but then falters and drops back down again, fluctuating from 0.04 up to 0.5 or so and back - generally all over the place. Number 2 O2 sensor stays fine around 1v.

I'd come to the conclusion that a faulty number 1 O2 sensor was being detected by the PFC and it was overfuelling to compensate (limp home mode). But I've tried turning the O2 feedback off via the PFC menu but it made no difference. Was gonna remove the O2 sensor and clean it, refit and see if it made a difference... ???

It's pretty wierd. From start AFM 1 & 2 both read circa 1.3v and both O2 sensors are fine at around 1v. Then after a minute or so, O2 sensor 1 drops to 0.04v and AFM number 1 drops to around 1v. The revs rise to about 1,370 and O2 sensor number 1 fluctuates, but generally is very low, AFM1 stays around 1v with AFM2 at 1.3v, O2 sensor number 2 stays around 1v.

Next step was to clean O2 sensor 1 and see if it made any difference... but as turning the O2 feedback off on the PFC seems to have made no difference do I now conclude that it's NOT the O2 sensors, and I'd be wasting my time trying to clean 'em??
 

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The O2's are only used for idleing and cruising. I turned mine off, althought they worked ok. When they are turned off, the V will still be displayed.
 

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If you turn the O2 feedback off, the lamda sensors are not used for anything. Not need to remove / clean / smash / worryabout

Lamda voltage oscillating between 0.0X and about 0.4V is normal operation when sensor is seeing stoich fuelling (14.3 - 14.9ish AFR).

Lamda sitting at 1V is either internal-short (aka dead sensor) or about 7:1 AFR!!

MAF voltage should be around 1V on Z32 or 1.3V on Std MAF. Upto 20% difference between signals would be `normal` (Broadly speaking).
 

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Discussion Starter #10
Yeah - std AFMs still on the car, so I'm assuming AFM2 at 1.3v is fine...

So here's the wierd thing - following figures DO fluctuate a bit up and down, but largely this is where they sit:

Cylinders 1, 2 & 3
AFM 1v
O2 0.04v

Cylinders 4, 5 & 6
AFM 1.3v
O2 1v (ish - fluctuates a bit)

So which of these look wrong then??
 

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At the risk of repeating myself, O2 sitting at 1V is a F***ed sensor, however IF you disable O2 feedback this will have zero impact on the engine.....

MAF voltages look OK.
 

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Discussion Starter #12
LOL Sorry ExScoobyT - so I can forget about hoping to change the 1v AFM and thereby curing the problem, then?

So we've ruled out sparkplug failure, O2 sensor failure (although one is definitely f**ked but with the O2 feedback switched off on the PFC this won't cause the idle to rise) and faulty AFM (as you say 1v and 1.3v looks fine). Have also retro fitted the factory recirc valves, thus removing a leaky BOV from the equation too.

I've had the engine running and squirted WD40 all round the intake gaskets with no appreciable increase in rpm, as well as squirting it round every connection in the intake system - again no increased rpm that I could detect.

What else is there left for me to DIY check? Coils? How can I check that a coil is running ok? Anything else?
 

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Jim27 said:
LOL Sorry ExScoobyT - so I can forget about hoping to change the 1v AFM and thereby curing the problem, then?

So we've ruled out sparkplug failure, O2 sensor failure (although one is definitely f**ked but with the O2 feedback switched off on the PFC this won't cause the idle to rise) and faulty AFM (as you say 1v and 1.3v looks fine). Have also retro fitted the factory recirc valves, thus removing a leaky BOV from the equation too.

I've had the engine running and squirted WD40 all round the intake gaskets with no appreciable increase in rpm, as well as squirting it round every connection in the intake system - again no increased rpm that I could detect.

What else is there left for me to DIY check? Coils? How can I check that a coil is running ok? Anything else?
If it's a coil playing up (firing on 5 cylinders) the engine will run like a deranged, out of balance Impreza. I'd say it's definitely not that (having already had a coil fail on me.)
 

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lightspeed said:
Or buy a lambda sensor socket - basically a deep socket with a slot up the side for the wire. Saved me a few skinned knuckles over the years.
Luxury!! :p
 

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I would suggest either the idle speed control valve or a misaligned throttle plate - near closed throttle a very small change in throttle plate rotation can have quite large changes in airflow......
 

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Discussion Starter #16
Cheers for the input ExScoobyT - few things bother me though.

From cold the idle is fine (sort of). You'd normally expect a cold start up to see the idle a little high, then dropping as the engine warms up. But cold idle is around 960rpm, then rising to 1,370 after 60 seconds or so. If a throttle butterfly plate was misaligned, or if the idle control valve was set too high, then surely the high idle would manifest itself immediately at start up rather than waiting for 60 seconds or so...?
 

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Jim27 said:
Cheers for the input ExScoobyT - few things bother me though.

From cold the idle is fine (sort of). You'd normally expect a cold start up to see the idle a little high, then dropping as the engine warms up. But cold idle is around 960rpm, then rising to 1,370 after 60 seconds or so. If a throttle butterfly plate was misaligned, or if the idle control valve was set too high, then surely the high idle would manifest itself immediately at start up rather than waiting for 60 seconds or so...?
Have you considered the PFC may be playing up? They have been known to loose their settings.

Want me to post you a std ecu to stick in, just to see if it idles normally?
 

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Discussion Starter #18
Yes, I've got a standard ECU but I'd have thought that with 264/264 cams and 550cc injectors the standard ECU will have trouble enough maintaining a stable idle...?
 

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Jim27 said:
Yes, I've got a standard ECU but I'd have thought that with 264/264 cams and 550cc injectors the standard ECU will have trouble enough maintaining a stable idle...?
I'm sure it'd be fairly lumpy but it'll still highlight whether it's the PFC causing the revs to rise. It's a cheap test so worth a go.
 

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Cams should not upset the std ecu significantly and it will be a bit rich but the std ECU should still be able to control the rpm`s ok.
 
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