Avcs Doesn't Engage Until After A Few 2Nd Gear Squirts To 5000Rpm.
 

So I have an issue with avcs not engaging until after I do a few slow slow load drives in 2nd or higher gear to 4000-5000 rpm then it's happy until I turn off my car

Even if I turn the car back on right after, I need to do the above a few squirts to 4000-5000 rpm and avcs works and functions like normal.

This happens on both banks at exactly the same time.

2002 sti (bugeye) avcs oil filters have been removed, standard ecu, although remapped using carberry speed density rom.

Any solutions or suggestions?

Cheers

Have you considered the neutral position switch is going intermittant? Not an uncommon problem. I am suspecting the switch in my 03 STi and will be replacing it at a clutch change next week.

JohnD

I did, but cruise control still seems to function during that period of no AVCS...which should indicate the NPS is working...

And logging shows it's in 6th gear in neutral and 0 in gear, which I gather is normal?

Although I may have to triple check that.

Yes but thats on cruise. The nps can drop in and out during hard accereration if its worn

I assume you've seen this? It's from your part of the world!


JohnD

Would a faulty nps show up on a fault code scan?

Thinking of taking my car to the garage, sometimes feels fast and other times doesnt feel very fast at all.

what oil do you have in and when was it changed ?

I use penrite 10w40 racing tenths (high zinc) Change every 4000km. Maybe the oil isn't thick enough?

Mrt is talking about the banjo bolt filters.

Once avcs starts working it stays working until I turn the car off. So it's not intermittent after it works. Rr logger seems to know when the car is in gear.

I'll try by passing the nps soon and see what happens.

How would you know the avcs isnt working other than data logging?
Cheers Ian.

Way more lag in 1st and 2nd gear.

Drives like a different car when AVCS is working :) Most noticeable low to mid range...don't think AVCS does much top end.

Difference in it working and not working would be noticable in all gears.
Variable valve timing is the clever way of overcoming the requirements of the engine at both low rpm and high rpm/load. Back in the 'old days' you needed a cam that gave a lot of valve overlap to produce good top end power but this would give a poor low rpm performance and poor driveability so manufacturers would use a cam which gave a reasonable compromise. Now, with VVT you can have the best of both worlds.

JohnD

I'm aware of what avcs does Thanks.

I only Mention 1st and 2nd because by the time I go into higher gears I'm not usually giving er on the street :)

Still no solution though

Picking the car up after a clutch change tomorrow which also included a neutral position switch change while the gearbox was out. I'll report on any wear on the plunger on the old switch.

JohnD

I don't think it's the NPS.

In the rom I inverted the NPS signal, and still does the exact same thing...unless if the NPS works in a different way than I think it does. And in the logger it shows the car in a gear number now instead of 0 and 0 in neutral instead of how it was before.

Cruise control still works

My AVCS has a certain "trigger" associated with it to engage and start and continue working until the car is turned off, and that trigger seems to be a 2nd or 3rd gear run to ~4000-5000, doesn't need to be at WOT, but enough to get it to build up some boost, then AVCS will start working and advancing intake timing as normal, until the car is turned off, then it'll have to start all over again. So it's not an issue to tune, once AVCS is working, just every time you turn the car off, gotta get some load on the engine and AVCS will start working.

Did more logging to try and figure it out:

On the logger this is what I'll see, turn on the engine and both banks at 0 degrees, and they will stay at 0 degrees until AVCS is working, but unless if I do the above, AVCS will not work, even on high load low rpm. Once it is working it'll advance as the map tells it to, then at idle it'll happily drop back down to 0 degrees.

When avcs is not working the ECU is not sending ANY signal to the solenoids to advance or retard, but when it is, all is happy

No AVCS related codes, and they are not disabled in the rom.

I've tried the following:
Inverse the NPS in the rom, which makes no difference for AVCS
Remove banjo filters
Different oils

*sigh*

The plunger tip shows some wear but I've no way of knowing if it is significant without a comparison.
One thing I did notice was that on connecting an ohm meter to the plug, it was open circuit without pressure on the plunger changing to closed as the plunger was depressed but went to open circuit again with the plunger fully depressed!:wonder:

JohnD

Interesting. I think it should be one or the other and not as youve described. Did you test the new one?

Yes. Can't remember that going open circuit on full depression.

JohnD

Hmmmmmmm....

So it could be the NPS and the value I'm changing might just only have to do with showing what gear it's in...then as I accelerate it somehow works, then when I turn the car off somehow that makes it not work again?????

Does anyone have a picture of the connector that I'm supposed to join the wires together to bypass the NPS?

avcs needs to meet certain thresholds before it starts working...
coolant temp...load..NPS... etc
found this out the hard way

AVCS thresholds
 

Sorry to bring this thread back from the dead but...

Kay (Or anyone) - Do you have any idea what the avcs thresholds are?

Myself and several other guys I know have the same issue in that our AVCS simply does not engage. I've replaced my NPS, removed/cleaned/tested the avcs valves and removed the banjo filters but no dice... When logging, I see the AVCS at 0 at idle and sometimes while driving it goes up to say 2. All of us have wrx Blobs.

I must admit I haven't logged any data for a while but I can try get more details.

Hope someone might have some answers :-)

Probably the wrong NPS

https://www.scoobynet.com/engine-man...ange-help.html

I had similar issue,

Turns out there are two NPS sensors,

One reads 1 for neutral & 0 for in gear

The other reads 0 for neutral & 1 for in gear


This can be changed though the map by inverting the signal.

Quick update,


Turns out the fault was the Neutral switch all along,

The part changes after 2005 and the polarity changes,

My car thought it was in Neutral when in gear and vice-versa,

Replaced with the correct part and all is well again you can see my avcs is operating and the pops and bangs are back :)



https://cimg3.ibsrv.net/gimg/www.sco...a9cd96a3b3.jpg


https://cimg5.ibsrv.net/gimg/www.sco...b27d73298e.jpg

https://cimg6.ibsrv.net/gimg/www.sco...fd42a7c4bb.jpg

Thanks SmurfyBhoy

I have heard about the polarity issue as well. I can't change it via the map as my ECU is ECUTEK locked. Any idea if I could just try cut and splice the wires? I am planning on getting a re-map at some stage.

I do know that that my new NPS is 1 in gear and 0 in neutral. I couldn't test the one that came with the car is it was totally poked.

I assume the ECU is the only thing that cares. Reason I ask is I have a tad bit of a complicated setup after I ran bearings and got absolutely shafted by a supplier. Basically in South Africa we get AUDM spec cars. So I have an 03 blob (Which is already not all that common as I understand) running with JDM V7 STI heads. The AVCS was actually moved across from my old heads so come to think of it the ECU should see it all as the same and this is a mute point lol.

I guess the next thing would be to try invert the NPS.

Out of interest, when your AVCS was dead, did you ever see if go higher than 0? Even by 1 or 2 degrees?

I Just realized that doing it via the ECU or getting an inverted switch is the only was to do it. A switch is a switch, no matter which way around you wire it :lol1:

I'm afraid your correct bud,

Yes i got a little amount of AVCS on logs but only 1 or 2 it showed but thats's all.

Best ask ur mapper its a 2 min job to invert in the map,

There are ways around ECUtek locks ;)


https://cimg9.ibsrv.net/gimg/www.sco...9982d0dcfb.jpg

Thanks for the input SmurfyBhoy!

Again, bringing my dead thread back from the dead lol.

So my issue is still present...

In a nutshell, this is what I have done over the past while when I've had time to troubleshoot.

Tested/cleaned OCV's
Many oil changes. Currently running LiquiMolly 5W40 Fully Synthetic. Time for a change this weekend though.
Replaced cam gears with known working ones.
Replaced NPS (I still need to try invert the signal in the MAP, any info on how to do this would be amazing - We didn't have the invert option in romraider)

I managed to pull my ECUTEK map after all and confirmed that the VVT is mapped.

There are now 5 or 6 of us in my neck of the woods, all with blob's, all with the same issue sigh. Problem is we all live miles apart and very few of the guys have access to kit for logging etc.

Any chance you could post a log similar to your first one? I noticed that the Gear sensor keeps saying 6 and occasionally 2 which is what mine is also doing. Wonder if your NPS fixed that as well.

This is also a snip of a log this morning to further illustrate the issue.


https://cimg3.ibsrv.net/gimg/www.sco...0bb69719a6.gif

If you cannot invert the signal in the Rom,

I think your only option would be to source the other type of NPS

If you know which part no you have you can work out what you need,

ECUtek rom may not have the menu which allows this to be switched round,

NPS should read 0 when the AVCS works if you go by my Logs ?