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logan25

The Infamous 2,800 RPM Stutter

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Thought I might try tackle this issue with the free time. 

 

I posted what I thought was solution of this on another thread of mine, turns out it didn't really last. 

 

2006 Legacy GT 6 Speed EJ20Y. Has the infamous stutter at around 2,700-2,900RPM, no misfire reported but it feels like it. 

 

I did a T mod onto the BPV line to change the FPR vacuum source, issue came back. I have now since reverted it back to it's original location. 

 

Interestingly enough, the only time I can get it not to stutter at this RPM is to take off the vacuum line from the FPR, and then re-sit it on. It will drive fine for the next 50-100kms or so, then return to it's stutter.

 

Not sure for direction to take from here, but may change the FPR with another factory one, along with the vacuum hose. Otherwise might look more into Romraider to see if I can find any issues, last I checked was fine. Any particular values which should be checked?

 

Any thoughts or previous jobs which have worked out there?

 

I have only driven an auto in this same generation, and that didn't stutter like this particular case. 

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Hey,

 

I had this problem for YEARS.

 

Tried all the tips and tricks I found on the web and nothing helped. Cleaned/replaced Maf sensor, cleaned intercooler and throttle body, changed turbo inlet pipe and throttle body pipe, replaced crank sensor, used Lucas fuel additives, feed my FPR vacuum source to a different one, replace FPR etc etc. It's been so long and so much money has been spent i've lost track of the others ive tried.

 

What fixed it for me was when I had my tranny fluid flushed and replaced in January 2020 (due to a P1710 problem) and now it's permanently gone.

 

Hope this helps you :)

 

Cheers,

 

 

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Not sure whether it really matters or not, but the better way to do it is to just swap the BPV and FPR vacuum source locations rather than teeing. They're not the same size vac hose so not sure how it will go with the factory parts. Worked fine for mine with the aftermarket BPV and FPR though. 

 

Have you had it tuned? It could be that there is a learnt timing pull at that point that may be making things worse.

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1 hour ago, Andy_Mac said:

Not sure whether it really matters or not, but the better way to do it is to just swap the BPV and FPR vacuum source locations rather than teeing. They're not the same size vac hose so not sure how it will go with the factory parts. Worked fine for mine with the aftermarket BPV and FPR though. 

 

Have you had it tuned? It could be that there is a learnt timing pull at that point that may be making things worse.


That was my original intention, straight swap, but for the adapters and parts I could get local made it easier to do the T mod, maybe have to look at this way instead. 
 

Haven't got round to tuning it yet, might try pull up the LV tomorrow (Still learning how to use RomRaider, always used to use BTSSM, but the Nexus died). Still interesting of how a simple pull off the vacuum line and resit fixes it temporarily. Thats why testing is difficult, think its fixed but it just comes back after time.

4 hours ago, romeyromes said:

Hey,

 

I had this problem for YEARS.

 

Tried all the tips and tricks I found on the web and nothing helped. Cleaned/replaced Maf sensor, cleaned intercooler and throttle body, changed turbo inlet pipe and throttle body pipe, replaced crank sensor, used Lucas fuel additives, feed my FPR vacuum source to a different one, replace FPR etc etc. It's been so long and so much money has been spent i've lost track of the others ive tried.

 

What fixed it for me was when I had my tranny fluid flushed and replaced in January 2020 (due to a P1710 problem) and now it's permanently gone.

 

Hope this helps you :)

 

Cheers,

 

 


Interesting,

 

I had an auto (07 model), never had this issue.

 

I don't know much about these manual transmissions, but I guess a change of the gearbox fluid is an option. Not sure if the previous owner ever had it done.

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RomRaider can be quite a pain to install and get working correctly but it really is what you need to be able to get a LV readout.

 

What are you meaning by resitting it? Removing it and reinstalling?

 

Gearbox on a manual won't be the cause at all. 

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40 minutes ago, Andy_Mac said:

RomRaider can be quite a pain to install and get working correctly but it really is what you need to be able to get a LV readout.

 

What are you meaning by resitting it? Removing it and reinstalling?

 

Gearbox on a manual won't be the cause at all. 


When I say 'Resit' which fixes it, I mean all I do is pull off the Vacuum line of the FPR, then simple put it back on. It may sound ridiculous but it genuinely does fix it for the next 100km or so, which has me puzzled. 

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Yea that sounds pretty out there. Unless the FPR is internally jamming up and just the shock from you pulling it off and putting it back on temporarily loosens it up.

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Posted (edited)

So I changed over the FPR, initial testing seems to have got ridden of the stutter, but again, from previous experience I won't know if its fixed until done 100km or so. Been doing laps around the drive way to suffice for now. 

 

Finally got Rom Raiders LV to work. Before doing the work, my fuel trim highest was -13.5. After doing the work, dropped to 9.5-10.8.

 

Why the fueling numbers are out are still so negative are beyond me. Maybe my next task is to pull the turbo off, and while I am there get the banjo bolt filter out. 

 

Out of curiosity, when doing logging, what data value should I be using (4 byte or 2 byte etc). When selecting both, give slightly different values. 

 

Log: https://drive.google.com/open?id=12-rqXJYHLUH1T5PfLt0l9q0kKnsicB-p

 

 

Edit: Just repurchased a tactrix cable, might just bite the bullet and get it properly tuned once and for all, especially now I have lots of free time. Will be interesting to see if Dave can tune this ECU. In my initial contact with him he opened it and said he could tune it. 

romraiderLTV_20200410-154520.png

Edited by logan25

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Have you got the stock intake still? Those figures would indicate either you have a decent air leak, aftermarket intake or MAF/O2 sensor problem.

 

2 and 4 byte should give very similar data. The only downside to using 4 is it uses more data so if you use a few 4 byte parameters you’ll find the read speed will drop significantly so data points will slide further out of sync with each other

 

He can tune it for you, you just need to flash a different ROM to the ECU first as it is the same one as mine. There is an 07 ROM available that worked perfectly for me once I finally got round to flashing it.

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Yes everything is still stock. Have replaced both the MAF and O2 sensor before, boost leak test done by Crowesport etc. Had replaced the fuel injectors, redone the intake manifold seals, change intercooler. Nothing fixed, last we decided was just to tune it to see if it goes away. After all the work I did, it did drop from 15 to 13 and recently to 9-11 range. 
 

Question regarding the banjo bolt for the turbos. On the facelift models, can these be taken out with the turbo still on? I know they have their own oil supply line, compared to the prefacelift which it was shared and difficult to get at. Wondering if the turbo banjo bolt filter will be a easy job or need to pull the entire turbo off. 
 

Will let dave know prior to tuning to we can start in the right direction. So you just essentially installed a stock 07 image and tuned from that? 

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Wouldn't expect a blocked banjo bolt to be causing any of these issues. What about the fuel pump? It could be worth getting a cheap aftermarket fuel reg and gauge just so you can confirm that is all alright.

 

Yea just flash it over. No different to flashingamy other ROM

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Posted (edited)
10 minutes ago, Andy_Mac said:

Wouldn't expect a blocked banjo bolt to be causing any of these issues. What about the fuel pump? It could be worth getting a cheap aftermarket fuel reg and gauge just so you can confirm that is all alright.

 

Yea just flash it over. No different to flashingamy other ROM


Banjo bolt filter removal more just preventive work. Not related to the fuel issue above. Did work on an 04 a few months ago which lost its turbo due to blocked banjo filter. Actually it chewed through 3 turbos on the previous owner within 200km. 

Thats an option I can explore regarding fuel pressure. Will have to wait for the shops to open up again. 

I see the fuel pump can be access under the seat. I might just replace it tomorrow as have a ‘carcass’ of another 06 LGT sitting there. Needs to be taken to a scrapyard anyway soon.

 

 

Edited by logan25

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A lot of facelift ones seem to have most of them removed already, think dealers we're doing it early on when they realised the issues. Worth checking anyway. You can't get the one above the water pump as the timing cover prevents it fully coming out unless removed.

 

The fuel pump is a bit of a pain. Replaced mine today.

Just make sure you have a bunch of flatheads handy as they're the easiest way to prevent the clips on the lower part from clipping back in as you wiggle it off. 

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For the who do the Turbo Banjo Bolt filter in future. You do need to take off the turbo, as its connected to the same supply line as the AVCS Banjo's (I think that what they are). 
 

Mine was surprisingly clean for 180,000km, but still glad to have got it done. 
 

Also changed all the intake piping that runs post MAF to Turbo - Just in case it was leaking. That was more of a mission, getting those pesky clamps off which are underneath the intake manifold. 
 

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Posted (edited)

In a bit off an off topic question regarding SI Drive.

 

When the car is cold (ie blue coolant light on), and operating in intelligent mode, why is it the car boosts more, than when warm? From memory, a warm car in intelligent peaks around 3-4 psi boost, but mine when it is cold will

let it go upto 12 ish if the foot is flat. I never let it do it usually but have noticed it can. Seems like ECU is reading something backwards.
 

This seems odd since it should be limiting boost more while cold (considering Sport # cant be selected).
 

 

Also, after a drive on the open road to the supermarket, did a LV shot, and have seen the lowest fuel trim reading since I have owned this car. Hopefully it keeps dropping in this trend...

romraiderLTV_20200412-154643.png

Edited by logan25
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Don't think the AVCS stuff can do much until warm so could be to do with that not being able to hinder it as much as when warm maybe??

Wastegate spring is usually around 7psi so It should always be able to reach that unless timing is crazy retarded. 

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19 minutes ago, Andy_Mac said:

Don't think the AVCS stuff can do much until warm so could be to do with that not being able to hinder it as much as when warm maybe??

Wastegate spring is usually around 7psi so It should always be able to reach that unless timing is crazy retarded. 


It always feels ECU limited. For example, just as the temperature (from memory 65 degrees or so) approached the end of the blue light it could pull high boost, but the very second the blue light disappeared it would limit it self back to

low boost as soon as you reapplied the throttle. The process was almost instant. Always had me puzzled why it was like this. 

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Posted (edited)

So changed the fuel pump, not too much luck I don't think. Funnily enough the stutter is slowly coming back to the car at 2,800 rpm. 

 

But with regards to the fueling issue with negative trims, check out the 2 logs below. They both show the car at idle after a short drive, starts at -10, and while sitting there drops down to -5 range, then after a short drive around the driveway creeps upto -8. They tend to be all over the place.

 

https://drive.google.com/open?id=1QAp-LFdftk-EgqxnqcAdxJpWRznpNiMX

https://drive.google.com/open?id=1jhO4ItHK2TCMIL_74REzZEpaynWz7CXU

 

 

Before that I made a smoke machine to recheck for intake leak, nothing, as the boost leak test showed as well. 

 

I have just started the tuning process with Dave and awaiting his first Map to be sent. 

 

 

Edited by logan25

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Posted (edited)

More to finish this thread off and to help those in future if you had negative fuel trims at idle like me. 

 

So throughout all my testing I always had two MAF's which were known to be good and clean as were placed on other legacies and read fine after many kms of driving. 

 

What finally seemed to have swung my fuel trims to the zero or close about on the stock rom was a combination of things. One day I replaced the spark plugs, air filter and gave the MAF cleaner an extremely good clean for 10 mins. Since then the fuel trims seem to behave. The air filter in it seemed to be some repco brand so put in an OEM subaru one. 

 

Hoping is stays like this, makes it easier for the tune process. 

 

 

romraiderLTV_20200502-175533.png

Edited by logan25
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