Diagnosing rough idle

[Swanga]

Its been a long time since I had my last xr6t (2004 BA MK2 bought new) but ive recently picked up a 2003 BA Ute(done 192k) as a bit of a project and im just going through everything and tidying it up. Ive been scouring the pages on info relating to rough idle once warm and ive attended to some of the obvious as they needed to be done anyway. I.e It has new plugs, injectors serviced (one was rooted) and throttle body cleaned.

 

Its thrown out the codes as pictured (I think the first two have now been cleared after the service) which leads up to believe the timing chain is stretched and throwing out the vct. Would we be right in assuming so?

 

There is no engine light on.

 

 

 

[FiftyOne]

I would have to dig around for it but I believe there was a firmware update for BA's back in the day.  The VCT & soliniods could get a little gummy pushing the timing out so I think they programmed in a purge once the engine started to prevent them sticking? I think that was something like the story anyway, I stand to be corrected on that.   The connectors on the VCT are also brittle as hell so they may be broken & shorting a bit.

As for the rich/lean?  Bad o2, vac leak, intake gasket? But if a service cleared them I would focus on the VCT issue and check back re the tune

[Wyatt]

Have been chasing a rough idle and miss in my modded FG turbo. I've had the car for 2 years and it has been a consistent issue but not a major drama but recently doing my head in. The annoying part is when at operating temp, when putting car into park and then back into drive it hunts and stalls a lot. It has never stalled when left in gear while driving. Definitely worse since I changed plugs and gapped BKR7E down to .75MM (16 psi tune) as previous plugs had eroded to .9mm after a miss developed at high rpm/boost which sorted that problem. The old plugs looked all the same with an off white insulator and a lighter colour for 90+% of the strap. The motor doesn't jump around too much but there is an inconsistent popping sound to indicate the miss. I did also change the coils with genuine jobies. Fuel filter was changed and the motor uses no oil and does not blow white or black smoke, while inside the 3.5" tailpipe is black, there is zero soot/oil on the back of the car. The intake manifold doesn't seem to be the culprit as have checked tension on most of the bolts and spraying an accelerant around which did not change the note, throttle body has been cleaned/ gasket replaced which I thought made a difference, but I was mistaken. The pre cat O2 sensor seems to fluctuate between .1 and .9v as it should, although the wave does tend to stay at the bottom end and go close to 0 at times and torque pro suggests O2 sensor 1 is over voltage and the catalyst monitor ratio being above spec. From what I can make out, the injectors are 1000 kpm's. 

 

Car has a 465 high pressure walbro on the stock 4 bar reg, fuel pressures must be super high, I've order a GFB with gauge to get the tuner to drop in soon. I'm hoping this helps as it's recommended by some here.

Car had pump gears done inbetwixt with no change, so you would think the only teeth skipped are in my head.

 

Vehicle starts immediately when cold and after driven is a marginally slower to fire. Idle when warm sits mostly between 670-700 rpm. Wires going to cam sensor drivers side are not cooked, oil pressure when I tested a while back was good.

 

Did a compression test today to see if there were any clues there. From front cylinder 1 161psi, 2 156, 3 151, 4 150, 5 153, 6 147. Not as good as some of the results reported here previously. Leak down test not done.

 

I've spend some time on the webz trying to diagnose it but have come up short and ask if anyone has some sage advice. There are no hard codes that torque pro stores and or engine light illuminated at any time. When last tuned the tuner was not able to tune around the issue. Car previously had a 20 psi tune for a 4-5 months which was not overly aggressive ie full boost at 3500 fwiw. Power has stayed consistent at 370-375kw with the 3 dyno charts I have seen since being modded. 

[Wyatt]

Thought I'd try another post with less questions and more info.

 

Car starts and seems to run without misfires while in open loop, timing advance around+15. Once it goes to open loop the farting and hunting starts and below screenshot shows the advance goes quite high. 

When I pulled the new plugs for the comp test which was an idle only warm up (lockdown life), they were very white and the first thing I did was to try and wipe some off but it was stuck like paint. I didn't think much of it at the time, being uninformed.

I didn't take a photo unfortunately, there's a shot of the oldies below.

 

Anyways, played with my toy and got the below info @ hot idle. The tune has has afr's below 12.5 from above 2000rpm. 

 

The long term actual av econ is about 10% less than what is displayed on cluster 16.4l/100, not sure if this is significant. Can't help thinking the rail pressure and return valve undersize could be a factor, but then again sh!t and clay look similar 2 me.

 

 

Hope this helps if anyone is interested,

[El Andrew]

Have you tried a new O2 sensor? Only $60 or so and can cause some stalling issues. If it's never been done it really is a service item anyway.

[Wyatt]

Cheers @El Andrew

The O2 sensor 1 does mostly oscillate fairly evenly but occasionally stays down nears the bottom of the scale. Like you said, a service item anyway. I'll give that a crack. 

 

I need to look at the wavy lines longer to see if there is any correlation I can spot, so far when it splutters/stalls the timing value goes up over 50.

My work has pretty much dried up due covid bs, so have heaps of free time to frig around.

I did look through your posts in the DIY tuning thread about 2 years ago re open loop idle and have added to my notes to discuss with tuner. I'm not sure how the reduced plug gap makes it worse. Runs great at wot, but I won't be doing anymore of that until this gets sorted. Timing values were quite high somewhere around 35-40. I don't know if the data is much good though.

 

I guess if it can idle without misfires cold then it can also idle well when hot.

 

Just to add there are no faults I can see on cluster or toy obd 2 app. All lights are functioning normally on dash.

[Wyatt]

So changed plug gap back to .85mm from .75 and idles better and stalls less when moving between park and drive when hot. Misfire count is much less but still there.

Thought detaching PCV at intake and blocking would be worth a try to rule out a leak from that area (but we know what thought thought) and it does much the same but maybe has a little more poke down low. Roads were wet and seems unwise to flog it atm, so testing was only up to 4psi.

 

The change that I noticed was STFT moved in a wider band from around -10 to + 10 at the extremes and LTFT moved mostly to the downside with values as low as -15. Maybe this has messed with the tune somehow.

[Wyatt]

Just out of curiosity, how close should fuel econ as displayed on cluster be to actual usage?

[Wyatt]

Felt the need to take a look under the lid and check cams/timing etc to decrease the possibility of mechanical causes with the dodgy idle when hot.

Was very pleased to find everything was a much cleaner than expected and cams/rockers had no pitting, gouges or anything else undesirable that an untrained eye could see. 

After recently throwing in a new O2 sensor and MAP clean, which wasn't that dirty, with no benefit to the condition, am feeling more confident to pursue a tune fix. Does make you wonder why 2 tune shops can't work it out, albeit they're more aligned

to GMH stuff than the odd tricky barra.

Noticed I'm not alone out there with @Danny Ajder current thread.

 

KPM?

[Wyatt]

So finally got annoying bad idle/stalling sorted by Dave @CPV tuning in Mackay. Pleased to report it's purring like a kitten now with .7mm gapped plugs, gfb fpr + gauge and a fresh pcmtec 98 tune. ZF changes are firmer with 1 happy driver.

Couldn't get the boost in any earlier apparently, but it is much more responsive than previous and don't need to ring it's neck to feel the full bean flavour.

This must be a gtx64 wheel, which others have raved about, but doesn't seem that brill in this application. 

 

Great economy on highway for trip 1500Ks @ measured 10ks/l down and back including regular wot in amongst roadworks, railway lines, potholes n roadkill. There's something special about a decent T road trip