Power Fc Idle Problem

[tacker]

Guys,

have a idle issue with the Power FC. What is happening from what i can see on the hand controler in sensor check is that the engine is happy idling away with a AFR of low 13's.

Then the problem starts as the 02H on the hand controler turns black the AFR drops to below 10 and the poor old car stops. As this is happening i can see no blips with the voltage on the 2 x 02 sensors, nor on the 2 x AFM voltage, yet the AFR gose south and it stops.

Car runs quite happly with 02H with just the empty circle for about 8 to 10 seconds, but as soon as it turns black she stops.

would this have something to do with the closed loop operating as i no longer have the ACC valve on the car, which has been gone ofr some time and i never had this issue. I have replaced the two 02 sensors and it made no difference, although when i disconnect the 02 sensors the car idles ok.

any ideas.

[tacker]

bump

[paulr33]

id say removing the AAC valve is your catalyst - why did you remove this? to gain what?

under function select what have you set?

what 02 sensors do you have?

have they been replaced?

for BNR32 you must set 02 register to Yes under function select

if you select no it assumes you have BCNR33 02 sensors

BNR32 = titania 02 sensors and BCNR33 is normal 02 sensors

so if you have used normal 02 sensors then you need to set accordingly.

[tacker]

Cheers Paul.

I will look at the function select as you mention as i have never altered it.

I would say that i have the original 02 sensors both sets that i have tried as least.

I have have the acc valve off for some time and the idle has not been an issue for months until this problem appeared last week. By removing it i have cleaned up the vacum hose arrangement.

What does the 02H in the sensor check indicate when it turns dark as thats when the AFR goes very rich?

regards

[tacker]

any ideas which sensor controls the 02H on the power fc hand controller please.

[paulr33]

02H will lit up under sensor/sw check when the 02 heater circuit runs, as the name implies

02 Heater control

[paulr33]

hang on, its still the factory 02 sensors?

they would be toast for sure - can u borrow a set of bnr32 sensors from someone else?

or you have a working known set of 32 sensors and they do the same thing?

when did this problem start

when did it last idle ok

what was changed to make it not idle properly with the 02 sensors

[STATUS]

tacker pull the 02 sensors... they are pointless in most performance cars anyway (if the tuner has done his job, not just the power curve ). If the car is properly tuned they are obsolete and you will still get better fuel consumption (i know its a race car)

For now though:

Turn off 02 feed back and disconect sensors and see if problem persists, if it goes away then no harm no foul, just check your tune around the cruise area and around idle If your not sure which areas i can pull a screen shot from dtatlogit and highlight the areas to check over. I have plenty of cars without 02 sensors getting better than std economy.

[tacker]

Paul / Trent,

yes i have 2 sets of 02 sensors and it does the same with both with the 02 feed back option on or off. It seems to idle ok when hot with the sensors disconnected but will still stall when coming down from higher RPM to what should be the idle RPM.

It was idling fine some 2 weeks ago before i had to pull the engine to made some mods to the oil pick up on the sump extension. After putting it back in i have this issue, i cant see that i have done anything incorrect putting the engine back God knows i have enough pratice lately.

What i cant understand is that its has a 13:1 AFR until that bloody 02H turns dark then the AFR just keeps getting richer until it stalls. What i cant understand is what relationship does the 02 heater turning on have to do with the ECU then dumping in more and more fuel?

Tuner is saying the same thing Trent lets just get rid of them and retune the maps so it idles, as its at WOT most of the time anyway when on the circuit.

LOL and with fuel prices at an all time high of 50 cents a litre in Dubai i care not what the economy is. Trent i have data logit so if you can send a screen shot we will certainly have a look at these areas.

Thanks for the help guys i greatly appriciate it.

Chris

[paulr33]

i suspect its stalling cos youve removed the AAC valve

i just cant see how the engine will idle with the valve removed

the valve bypasses air into the plenum around the throttle body when its closed

if you dont bypass or let air in when the throttle body is closed, the engine is basically starved of air and will stall

the 02 sensor control and closed loop function runs and checks 02 feedback from the sensors

in runs in loops and also the 02 sensors need to be heated up, they dont just work

they must be warm, so they have a heater control system in them to heat up and stay warm

this runs periodicially, which is when the 02H circuit relay comes on

its prefectly normal for the 02 sensors to be peridoicially heated up in cycles so thats not a problem

why its making it richen up off the planet im not sure i suspept a wiring fault or something

if the signal to the FC from the 02 sensors is scrambled / out of range when it runs in closed loop

it might keep trying to lean out too much and basically makes it richen up

check the 02 co-efficient in datalogit, has someone changed it?

if its wrong the FC will try and aim for an AFR out of range (like what yours is doing)

from memory the 02 co-efficient in datalogit should be like 1.047 or something like that

unplug the sensors, turn 02 feedback off

then fix your stalling issue

[STATUS]

Tuner is saying the same thing Trent lets just get rid of them and retune the maps so it idles, as its at WOT most of the time anyway when on the circuit.

LOL and with fuel prices at an all time high of 50 cents a litre in Dubai i care not what the economy is. Trent i have data logit so if you can send a screen shot we will certainly have a look at these areas.

Thanks for the help guys i greatly appriciate it.

Chris

cool, i will get something together screen grab wise.

As far as removing the aac valve it is possible to tune around the stalling, i fit ALOT of GIZZMO Phenolic intake gaskets to race engines and on most of these engines especially SR's, the AAC valves are water fed and referrenced to compensate for temp (temp and intake = bad so it gets the ass ).... i remove the AAC quite regulary (on rb's too) but in doing so you need to find the perfect balance between timing around the idle point (drop in big timing numbers below the idle RPM to force the engine to increase rpm back to its normal position) and you need to increase the static throttle postion (on the linkage). It is a bit tricky but by the sounds of your tuner is on that path already.

[tacker]

Paul / Trent thanks for the help guys have had to travel back to Oz as my brother is crook andhad to pick up 2 front screens.

Still no better off so the tuner tells me, but we can count the PFC out as it doing the same with standard ECU and injectors. I am leaning towards a short in the loom at this point, or a boost leak some where. Still the same when the 02H turns on it goes to poo. Quite happy to sit and idle for some time until the heater turns on and without much of an increase in the injector duty it goes real rich say 2.9 to 3.1.

Paul,

it was indling fine for weeks enough time to get 6 hours on the engine before removing it, and surely with the linkage adjusted right it has to get a constant flow of air it the one part of this issue that cant change. Maybe the BOV spring has lost it tension and is unseating allowing the air charge to decrease will check that and some known AFM from another car. Will be back with more info when i hear.

Also going to remove the heater relay if i can find the bloody thing.

[tacker]

guys,

have found the problem and its got sweet fa to do with the Power FC. Seems the length of pipe between the AFM and the intake of the turbo is far to short. Once we installed some longer pipe the problem with air being pushed back out the AFM has gone idles fine now.

Not sure if other with hard pipe kits have had the same problem before. So it now i work out some way to extend the intake pipes or i change over to a MAP rather than MAF.

[Beer Baron]

good stuff. what type of intake hard pipes were you using?

[paulr33]

i wouldnt have picked that

but others have seen whacko pipework cause other turbulance issues

the most common with custom whacko piping is the turbo chuffling or shuffling

[tacker]

tuner is telling me that this is why the stock intake pipes are corregated to reduce this effect, basically makes the pipe length longer.

Hey BB how are things? Got your big engine yet? I brought it of one of the forum sellers and i cant complain about it for the price, infact rather chuffed. I dont think that the pipes are all to blame i think that is just going to be the easy fix. It would appear that the combination of cams, cam timing, a lot of head work, removal of ACC valve and tune have all played a part in this saga.

Going to try and fit up a section of the stock pipes and get the filters out of the engine bay and into some cold air, so may get a small benifit out of this after all.

[femno]

Ha was just going to suggest the afm-to-close-to-turbo scenario.

It bloody happened to me running a 3071R .63 on a SR, the flamin mongrel was spitting air out on idle, couldnt believe it when we actually found the prob. (bout a week later after checking every damn wire etc)

[Beer Baron]

tuner is telling me that this is why the stock intake pipes are corregated to reduce this effect, basically makes the pipe length longer.

Hey BB how are things? Got your big engine yet? I brought it of one of the forum sellers and i cant complain about it for the price, infact rather chuffed. I dont think that the pipes are all to blame i think that is just going to be the easy fix. It would appear that the combination of cams, cam timing, a lot of head work, removal of ACC valve and tune have all played a part in this saga.

Going to try and fit up a section of the stock pipes and get the filters out of the engine bay and into some cold air, so may get a small benifit out of this after all.

going good mate. yes got my fancy engine sitting in the garage. ARC cooler and nismo AFMS and a few other bits arrived this week so I've nearly got everything I need to bolt the whole show together. can't wait. I've been playing with the silvia, the RX7, the 34 in the meantime but now I think it's time to get back to the main game and do something with the 32.

[Angus Smart]

Hey Chris,

did you happen to get that Cf shaft back yet?

as for the acc valve? is that all the shit under the intake side of the motor? can it be removed easily? and does it cause problems? (other than adjusting the throttles to idle) i dont have afm's and i use fcon pro v

Glad you sorted the problem!

and Richard, haha geeee no problem keeping you occupied with toys!!

Andrew

Edited September 5, 2008 by Angus Smart

[tacker]

nope Andrew vivid just gave up and gave me my money back after some 5 weeks of waiting.......you have yours yet?

yer it can be removed but you have to get inventive for vacum connections thats the only issue i have had. It idles fine but it can stall coming down from a around 3k free rev to a 1100 idle other than that with the o2 sensors off it idles fine and a whole bunch less connections on that side of engine i can even see the block now :-)