2zzge rough idle and stalling

[Lith]

Had a quick Google and it looks like it is a narrow band. Does it read that voltage at idle etc? If so then there is something wrong with how your O2 sensor is working or passing it's signal to the ECU , imho. It should be reading around 1volt at idle, any lower will make it think it is rich and it will try and lean it out and vice versa for if it is above 1 volt.

It sounds like it keeps leaning it out and never succeeds in getting it to it's target of 1.

Could be wrong but it would be where I would put my focus

[captain crescent]

Yea that voltage is at idle . I swapped the o2 sensor from my daily and still reads the same. i disconnected the o2 sensor left it unplugeed and ran the car with scan tool on it reads 0% for fuel trims and for the o2 sensor obviously. but still runs the same at idle with its stutter but as soon as i plug it back in the numbers creep up to the -20.3 again.

[Lith]

Have you had a wide band on it to get an indication of it's actual AFRs? Could either actually be running rich, or maybe some weird wiring issue

[captain crescent]

I Havant as yet I will have to try and get hold of one to see.

[jaypines]

did you try to swap the whole throttle body as well? other things to check: injectors, catalytic converter blocked?. also try compare maf output waveforms/voltages vs injection duty cycle?

[captain crescent]

The thing that no one understands is why it stalls when it does (driving conditions) and doesnt seem to stall at idle.

[captain crescent]

did you try to swap the whole throttle body as well? other things to check: injectors, catalytic converter blocked?. also try compare maf output waveforms/voltages vs injection duty cycle?

Didnt swap throttle body but ICV has been out cleaned etc.
Has no cat only one rear box muffler

[jaypines]

Didnt swap throttle body but ICV has been out cleaned etc.
Has no cat only one rear box muffler

try to swap the whole throttle body to see if it makes a difference. The TPS could have some off trace in the resistor film inside.

[captain crescent]

The throttle position sensor seems to work fine

[matt dunn]

Had a quick Google and it looks like it is a narrow band. Does it read that voltage at idle etc? If so then there is something wrong with how your O2 sensor is working or passing it's signal to the ECU , imho. It should be reading around 1volt at idle, any lower will make it think it is rich and it will try and lean it out and vice versa for if it is above 1 volt.

It sounds like it keeps leaning it out and never succeeds in getting it to it's target of 1.

Could be wrong but it would be where I would put my focus

If a narrow band O2 sensor reads 1V it's buggered, or more likely wired wrong, as they should never get that high.

Their operating range is 0.25V to 0.85 volts,
with 0.5 volts being Lambda 1.

Under normal conditiond withe enge engine held at 1500rpm no load,
the sensor should fluctuate between under 0.4v and above 0.6v
at least 6 to 8 times a second.

A constant voltage from the 02 sensor is not normal,
and they should read close to .8V if you give it a shoefull,
and then drop to around 0.3v when you lift off.

The thing that no one understands is why it stalls when it does (driving conditions) and doesnt seem to stall at idle.

No speed sensor signal will cause this under quick deceleration,
but I presume you have it working as they run like shit without it.

[captain crescent]

Their operating range is 0.25V to 0.85 volts,
with 0.5 volts being Lambda 1.

Under normal conditiond withe enge engine held at 1500rpm no load,
the sensor should fluctuate between under 0.4v and above 0.6v
at least 6 to 8 times a second.

A constant voltage from the 02 sensor is not normal,
and they should read close to .8V if you give it a shoefull,
and then drop to around 0.3v when you lift off.

The thing that no one understands is why it stalls when it does (driving conditions) and doesnt seem to stall at idle.

No speed sensor signal will cause this under quick deceleration,
but I presume you have it working as they run like shit without it.

The readings i am getting are off a generic scan tool so i am getting a semi stable voltage (I dont have access to a scope so cant really see what is happening within a second)

Are we talking engine speed or vehicle speed? it is intermittent when it cuts out and is not always under rapid deceleration normally just backing off whilst cruising at 100kms or so.

[matt dunn]

The readings i am getting are off a generic scan tool so i am getting a semi stable voltage (I dont have access to a scope so cant really see what is happening within a second)

Are we talking engine speed or vehicle speed? it is intermittent when it cuts out and is not always under rapid deceleration normally just backing off whilst cruising at 100kms or so.

You can check narrow band O2 with a multimeter.

Vehicle speed.

When you say it cuts out backing off at 100kms,
it is manual? as the engine should stay turning,
does it no go when you put the accell back down or are you pusinh in the clutch and it stalls???

Cant really see what you are saying?

[captain crescent]

Ok I will have a little look with a multimeter and see what it says.

When you say it cuts out backing off at 100kms,
it is manual? as the engine should stay turning,
does it no go when you put the accell back down or are you pusinh in the clutch and it stalls???

Cant really see what you are saying?

Im sorry Im not the easiest to understand at times i know what i want to say but doesn't always come out right lol.

So ill be driving and will be cruising around 100 kms if i start to slow down by taking foot off throttle completely or almost completely that's when I feel the engine has cut out if I put foot back on throttle it will start again with a small backfire from the exhaust . I do quite often put my foot on the clutch as an instinct then letting the clutch back out and open the throttle a little it does start. It does not do it all the time maybe 2 or 3 times in a hour of driving and seems to be more when the engine is warm.

[Lith]

Their operating range is 0.25V to 0.85 volts,
with 0.5 volts being Lambda 1.7

Oh shit oops, and sorry OP..... not sure where I got that idea, obviously don't play with narrow bands really so should have stated that.

A constant voltage from the 02 sensor is not normal

Yeah, the voltage range was the fail I had there.... Was assuming that if it were always well away from what I thought lambda is at idle then was a good indication something was up. The fuel trim probably got my blinders on which is silly.

[captain crescent]

Ok followers and bringers of great ideas and knowledge. Today i managed to get hotd of a toyota sst fuel pressure tester.

The fuel pressure reads 340kpa at idle (specs say between 304-343 kpa)

And after 5 minutes not running the pressure is 290 kpa (specs say 147kpa or more)

so this rules out fuel pressure in my mind. would this also count out leaky or dribbly fuel injectors causing more unburnt fuel and the leaning?

Am i still looking in the direction of 02 sensor and wireing?

[sergei]

There is one way to eliminate the O2 sensor: just have it disconnected.
Yes it will bring on CEL and will record a code, will also run in open loop mode.

[captain crescent]

There is one way to eliminate the O2 sensor: just have it disconnected.
Yes it will bring on CEL and will record a code, will also run in open loop mode.

I have run the car with the o2 sensor disconnected the car still has a stumbling idle . does this rule it out completely and the leaning reading and the fuel trim a side effect of somthing more sisnister?

[captain crescent]

Ok since im running out of ideas and I havnt managed to check the voltage on the o2 sensor properly . This is a list of data i pulled from each car and what the readings are.

Race car

Calc load 21%
coolant temp 75 deg
short fuel trim no1 -20.3%
long fuel trim no1 0.0
engine rpm (idle) 800 -900 rpm
ignition advance 19 deg
intake air temp 30 deg
Afm 2.58
tps 9%
02 B1 S1 around 0.700 -0.900
02 ft b1 s1 -20.3%
injector pulse width 1.8 ms
Iac ratio 32-43%
load sig off
idle sig on
total fuel trim #1 0.80
total fuel trim #2 0.50

Daily driver

Calc load 13%
coolant temp 80
short fuel trim no1 -1.6 to 0.0 (fluctuates)
long fuel trim no1 -0.8
engine rpm (idle) 800 -900 rpm
ignition advance 16.5 deg
intake air temp 39 deg
Afm 0 (goes to 2.58 off idle)
tps 11%
02 B1 S1 around 0.700 -0.900@idle
02 ft b1 s1 0.8 to -2.3%
injector pulse width 1.7 ms
Iac ratio 25ish%
load sig off
idle sig on
total fuel trim #1 1.01
total fuel trim #2 0.50


Hopefully this might help a eureka moment!

[crispy'86]

Not sure if you stated you checked the tps output and set-up? Also does your road car still run the cat still. Your race car doesn't run the cat? Does it have pre and post cat converter O2 sensors? If it does run both i suspect the post cat sensor will always show up as a constant voltage saying it measures after the cat.
also may pay to check the injectors if they leak, clamp off the return line and leave it sitting and check presure drop. Or alternatively remove the inlet manifold and check the injectors for leakage. Does the scan tool have a graph on it and can check different readings. i.e afm and O2 sensor? Can it perform an actuation test, may pay to try this too to give you an idea

[captain crescent]

Not sure if you stated you checked the tps output and set-up? Also does your road car still run the cat still. Your race car doesn't run the cat? Does it have pre and post cat converter O2 sensors? If it does run both i suspect the post cat sensor will always show up as a constant voltage saying it measures after the cat.
also may pay to check the injectors if they leak, clamp off the return line and leave it sitting and check presure drop. Or alternatively remove the inlet manifold and check the injectors for leakage. Does the scan tool have a graph on it and can check different readings. i.e afm and O2 sensor? Can it perform an actuation test, may pay to try this too to give you an idea

No I haven't checked the tps output etc but it looks OK from the readings.
No cat in road car and only 1 o2 sensor in each .The fuel rail has no return line and the pressure in the fuel line stays at 290 kpa for at least 15 minutes and didnt drop at all in that time. No the scan tool is not all that flash .But it can do actuation tests and have played with them a little, but it doesn't point to anything to be honest.