Slight missfire at idle 3.0R

Posts specific to the 3.0 litre NA H6 engine

Slight missfire at idle 3.0R

Postby Mariano » Fri Nov 09, 2018 3:20 am

Legacy 2005 3.0R Spec.B no codes. Car has sometimes slight missfire at idle when cold. Little engine shake and exhaust sounds odd. Also fuel trim rises at bank 1 only at idle high as 15-20. Cruising is fine and car pulls hard between 3500rpm to redline. Some stuttering sometimes between 2000-3500 rpm... Plugs, 02 sensors, maf are new. Also cleaned PVC valve, EGR and throttle body. No vacuum or exhaust leaks anywhere. Smog test looks normal. Only thing left is bad coil or injector. Subaru roughness monitor shows 0 missfire? :roll: Anybody had same issue? Sound exactly like this M3: https://www.youtube.com/watch?v=neM4w77x8mw
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Re: Slight missfire at idle 3.0R

Postby bigBADbenny » Fri Nov 09, 2018 11:28 pm

Can you log your alvs angles?
The symptoms sound similar to 2.0t & 2.5t avcs issues.
I’m no H6 expert but the timing chain guides can also cause issues.

Scroll down: https://www.google.com.au/search?biw=32 ... N6Vxs253mU

And: https://www.google.com.au/search?q=h6+t ... ent=safari

Worth a look for associated issues and fixes.

And I guess you’d want to swap coilpacks bank to bank to see if the issue follows.
Indeed logging per cylinder misfires would be good too, via ssm, tactrix or Btssm...
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Re: Slight missfire at idle 3.0R

Postby Mariano » Tue Nov 20, 2018 1:13 am

I cant get any logger to work with this car. Used freessm and both intake ocv looks identical operation. I think it may be coilpack. Have to take car for longer drive and watch roughness monitor. How to get learning view or romraider to work with this car?
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Re: Slight missfire at idle 3.0R

Postby bigBADbenny » Tue Nov 20, 2018 1:45 am

Romraider or btssm. Via vagcom, btssm plug or tactrix plug.
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Re: Slight missfire at idle 3.0R

Postby Mariano » Thu Nov 29, 2018 4:18 am

Ok, got btssm working. My OTG cable was faulty. Timing and fuel correction below. There seems to be some knocking between 2000-3500rpm just where I can feel it. Timing is retarded but why? Theres no missfires. VVT intake between L and R differs 1-3 degrees which is normal I think? Car has double AVCS but cant log exhaust side? O2 sensors act wierd, there is no constant fluctuation when cruising,idle or wot. When there is activity they go 0.1 to 0.9 usually just flat line or small 0.2 changes. WOT both sensors read 0.9v very quick, off throttle immediately goes to 0.1v. So they work and are new denso sensors. Car has raptor headers and full stainless exhaust. After 4000rpm car pulls well and adds timing as you can see. IAM 0.844.
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Re: Slight missfire at idle 3.0R

Postby bigBADbenny » Thu Nov 29, 2018 5:35 am

Log per cylinder misfires...
I guess you’d check for the usual suspects like inlet leaks, cracked plenum box, exhaust leaks...
Post a link to the log eg dropbox, google drive etc...
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Re: Slight missfire at idle 3.0R

Postby Mariano » Thu Nov 29, 2018 7:09 am

Yes..I fixed plenum crack two years ago. Cannot find vacuum leak, sprayed carb cleaner everywhere :D Also injector o-rings are new. No exhaust leaks. I thought that btssm shows missfire count on main screen? I will try to make better log of missfires tomorrow. This logging thing is new to me. Also have torque pro... Some people had problems with ecu injector controller and 02 sensor wiring loom? Information is limited and scattered around another forums...
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Re: Slight missfire at idle 3.0R

Postby flatsix » Thu Nov 29, 2018 7:16 am

hi i've not used btssm but some don't some of those learning view timing values seem kinda beyond normal ranges ? Especially the first row for RPM 0000
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Re: Slight missfire at idle 3.0R

Postby bigBADbenny » Thu Nov 29, 2018 4:10 pm

I’m unfamiliar with most h6 specific diagnostics, but I’d guess given the rpm range is at zero, the figures there could be ignored.
What’s possibly more relevant is the differences between banks in the maf ranges...
Post the LV in the relevant thread and maybe search the thread for other H6 LV’s for comparison.

All the info for setting up Btssm logging will be in the manual, and the threads V1 & V2 on LGT...
I’ll take a look when I’m in front of a laptop.

You want to log l&r vvt angles at say idle, 1700rpm and freeway cruise for a few minutes each, then compare for extreme angle difference or inactivity.

I’d say look up h6 timing chain rattle as well.
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Re: Slight missfire at idle 3.0R

Postby Mariano » Fri Nov 30, 2018 3:20 am

Here some highlights from VVT log. So there is difference between banks, mainly they go by few degrees difference. Sometimes it gets bad as 25 degrees difference. L bank which is bank 2 is ok but R bank1 comes behind. I swapped soleinoid from bank to bank, same thing. No timing chain rattle and if timing chain was not ok it would affect more bank2 operation because engine spinning direction? I previously checked OCV banjo screen bank2 for derbris but it was clean. Bank1 banjo filter is tight spot between oil filter and engine, haven´t checked that if there oil starvation in OCV. Managed to capture 1 missfire from bank2 cylinders 2,4,6. :roll:
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Re: Slight missfire at idle 3.0R

Postby bigBADbenny » Fri Nov 30, 2018 5:30 am

I use megalog viewer to analyse logs, the free version is very adequate to begin with.
You can easily expand or compress the time scale aka graph width to get a better idea of trending.
It’s better for the big picture. Even excel will do.

Link a log and I’ll graph it with the paid version: 3D scatter graphs.

Misfires suggests coil packs or plugs issues, swap the packs around to isolate those.
Inspect and swap around the plugs.
If the issues don’t follow, you might have rings issues.
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Re: Slight missfire at idle 3.0R

Postby Flat6Estate » Sat Dec 01, 2018 12:46 pm

Also, check that the MAP sensor hose is connected to the intake manifold.
Its a stupid little thing that easily comes off, and has caused rough idling on a certain H6 racecar
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Re: Slight missfire at idle 3.0R

Postby Mariano » Wed Dec 05, 2018 4:44 am

MAP sensor hose is tight. I think it´s timing issue. Let car idle about 5 min and engine was about 70c warm, first two accelerations car had no torque at all, felt like 1.6l engine. IAM is now 0.533. I logged that moment after idle, and it shows no activity in VVT soleinoids, 0 degrees that time. Later there was activity, here log if somebody can take a look.
https://drive.google.com/open?id=1GErSF ... LrjbebxL61
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Re: Slight missfire at idle 3.0R

Postby bigBADbenny » Wed Dec 05, 2018 5:11 am

I’ll take a look today, fatigue day, got my laptop here :)
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Re: Slight missfire at idle 3.0R

Postby bigBADbenny » Sun Dec 09, 2018 10:01 pm

Hey I took a look at the log.

I wanted to check: are you resetting your ECU at all? Before logging?
If so don't, and don't make any togs till 25klm of driving time to let the ECU relearn.

Not sure why you logged only vvt specific parameters?
You missed this bit: You want to log l&r vvt angles at say idle, 1700rpm and freeway cruise for a few minutes each, then compare for extreme angle difference or inactivity.

By that I meant just holding it steady, easy enough in idle lol, a fair bit harder at 1700rpm and easy in cruise natch.

Now the thing I noticed the last time I diagnosed a car with the 2.5t avcs issue, was that it was a bit flaky at 1700 but I could provoke the shudder by very gently veeeery slowly exploring the rev range between idle and say 2000 rpm.

anyhow here's the log as seen in the scatter graph view of megalog viewer.

Image

Anyhow that screenshot is just 3 different 3d scatter graphs of vvt angle difference vs rpm, or time, with a 0 vvt difference filter applied.

Image

This is the usual graph, split into three concurrent windows for comparision.

Now, there's plenty of VVT angle difference, but not quite enough to be causing the self calibrated systen to go into oscillation or shutdown... Or is there?

What I dont get is how your engine is even acheiving VVT angles with no OSV duty!

So perhaps being able to compare that event with other parameters might be handy,

Anyhow, perhaps try another log, with the usual H6 tuning parameters, these from a quick google search.

H6 logging parameters…

Vehicle Speed
Engine Speed
Intake Air Temp
Coolant Temp
MAF g/s
Engine Load (Calculated)
Throttle Opening Angle
Ignition Total Timing
VVT Advance Angle Left
VVT Advance Angle Right
OSV Duty Left
OSV Duty right
Per Cylinder Misfire 1 - 6
Front o2 Sensor #1
Front o2 Sensor #2
A/F Correction #1
A/F Correction #2
A/F Learning #1
A/F Learning #2
A/F Sensor #1
A/F Sensor #2
A/F Correction #3 and #4 maybe…

That might be getting towards too many parameters, if so, BtSsm allows for eg cloned profiles for different logging setups, rebooting from different backups etc.
Or just change parameters in you currently loaded profile.
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