Xdl for VY V6 - what do you see ?

160 And 8192 Baud Aldl
OZ38
Posts: 288
Joined: Wed Jul 01, 2009 7:18 pm
cars: VY V6 Commodore ute.
VS V6 Commo sedan.
VT V6 powered 4x4 Hilux ute.

Xdl for VY V6 - what do you see ?

Post by OZ38 »

Hi all in PCM Hacking land.

I am having some problems with my VY V6. Running rough at idle & from a cold or warm start up it will flare to about 1800 rpm then come down to about 500+rpm & almost stalling. It will rise up again & then shortly after do the drop in rpm to almost stall out again. The idle feels rough the whole time.
I did the usual service stuff when it suddenly started doing this - Cleaned the K&N air flilter, cleaned the MAF, Throttlebody clean, replaced the spark plugs, actually replaced all the coils with good ones tested via The1. Replaced the Fuel Filter. Always run on BP Ultimate 98 with the occasional bottle of Injector cleaner in the tank. 6 months earlier it had a new set of ignition leads (stock OEM) fitted. It seemed to start running rough suddenly on the long drive to work, 85km's one way on country roads with no traffic & only three bends & a single stop sign.

I have done a few logs using the V2 Logger, but I am not really sure of what is right or maybe wrong.
I managed to do one this morning capturing the cold start up. I idled till warm for about 13 + minutes before driving off out of works long driveway then onto the open road. You can see the first two dips in RPM straight after start up then it settles & warms up. The two wire 02 sensors are as old as the engine (original) at almost 300,000k's. I can't tell if there is a problems or not with them. Engine it great nic as it has always been fully serviced every 5000k's from new by myself.

Can someone look over the xdl and see if there is something there I should look at closer.

Adx is the recently modded one for the V2 Logger by VL400.

Cheers
Attachments
VX_DualA.adx
(135.24 KiB) Downloaded 318 times
VX_DUA07.XDL
(845.86 KiB) Downloaded 331 times
ejukated
Posts: 443
Joined: Wed Mar 04, 2009 8:52 pm

Re: Xdl for VY V6 - what do you see ?

Post by ejukated »

your fuel trims are way out of wack. Try unplugging the o2 sensors, pull the batt for a few mins and see how it drives after that. If its back to normal then the o2s need replacing. Also check for vac leaks etc.
OZ38
Posts: 288
Joined: Wed Jul 01, 2009 7:18 pm
cars: VY V6 Commodore ute.
VS V6 Commo sedan.
VT V6 powered 4x4 Hilux ute.

Re: Xdl for VY V6 - what do you see ?

Post by OZ38 »

ejukated wrote:your fuel trims are way out of wack. Try unplugging the o2 sensors, pull the batt for a few mins and see how it drives after that. If its back to normal then the o2s need replacing. Also check for vac leaks etc.
Thank you. I have checked all around for any possible vacuum leaks. Will do as you suggest & see what results I get from that.
Cheers
immortality
Posts: 3416
Joined: Thu Apr 09, 2009 12:31 pm
cars: VH, VN, VS, VX

Re: Xdl for VY V6 - what do you see ?

Post by immortality »

What was the ambient temp when you started the engine?

It looks like the O2 sensors don't show any cross counts until about 14 minutes even though target AFR's have been 14.7 and engine temp over 30°C from about the 2 minute mark so the engine should have been in closed loop operation. O2 sensors probably need replacement as a first port of call.

Also, twice during the cold start the commanded AFR goes really rich which coincide with the drop in RPM, why I'm not sure. Try doing the cold start with the AC off. Does this have a modified TB on it?
OZ38
Posts: 288
Joined: Wed Jul 01, 2009 7:18 pm
cars: VY V6 Commodore ute.
VS V6 Commo sedan.
VT V6 powered 4x4 Hilux ute.

Re: Xdl for VY V6 - what do you see ?

Post by OZ38 »

immortality wrote:What was the ambient temp when you started the engine?

It looks like the O2 sensors don't show any cross counts until about 14 minutes even though target AFR's have been 14.7 and engine temp over 30°C from about the 2 minute mark so the engine should have been in closed loop operation. O2 sensors probably need replacement as a first port of call.

Also, twice during the cold start the commanded AFR goes really rich which coincide with the drop in RPM, why I'm not sure. Try doing the cold start with the AC off. Does this have a modified TB on it?
Not sure of the ambient temp, it was early morning (06:45am) & the IAT was reading 18.5c for a long time.
Stock engine apart from YT 1.9 ratio rocker which have been on engine for 13-14 years, plus K&N filter. No modified TB. I have ordered two new 02 sensors. But that commanded AFR going rich on the cold start up as you have noted, does it whether the AC is on or off. The 02 sensors have no part in this period of the cold start up do they ?
immortality
Posts: 3416
Joined: Thu Apr 09, 2009 12:31 pm
cars: VH, VN, VS, VX

Re: Xdl for VY V6 - what do you see ?

Post by immortality »

You are correct that during the cold start open loop period the O2 sensors are doing nothing but warming up.
immortality
Posts: 3416
Joined: Thu Apr 09, 2009 12:31 pm
cars: VH, VN, VS, VX

Re: Xdl for VY V6 - what do you see ?

Post by immortality »

Looking at the logs again it may be the AFR going rich is a response to the RPM dropping below the target idle RPM.

Have you altered the butterfly stop screw on the TB at all?
OZ38
Posts: 288
Joined: Wed Jul 01, 2009 7:18 pm
cars: VY V6 Commodore ute.
VS V6 Commo sedan.
VT V6 powered 4x4 Hilux ute.

Re: Xdl for VY V6 - what do you see ?

Post by OZ38 »

immortality wrote:Looking at the logs again it may be the AFR going rich is a response to the RPM dropping below the target idle RPM.

Have you altered the butterfly stop screw on the TB at all?
No all stock, never touched.
OZ38
Posts: 288
Joined: Wed Jul 01, 2009 7:18 pm
cars: VY V6 Commodore ute.
VS V6 Commo sedan.
VT V6 powered 4x4 Hilux ute.

Re: Xdl for VY V6 - what do you see ?

Post by OZ38 »

Doesn't spark timing change if the idle drops below a certain point ?
immortality
Posts: 3416
Joined: Thu Apr 09, 2009 12:31 pm
cars: VH, VN, VS, VX

Re: Xdl for VY V6 - what do you see ?

Post by immortality »

Yes I do believe it does alter the timing to control the idle.

The strange thing is our VX has always done something similar, starts and the idle drops rapidly and then recovers. I changed a number of things in the tune to compensate but never got to the root cause of the problem as I thought it was just a quirk of the later model start sequence? Our one got worse when I fitted a larger TB that originally came off a VS which has a smaller IAC passage through the TB.

Did this problem start after you serviced the car? Maybe you have bung lead or plug? Worth checking.
Post Reply