AVCS issue
 

Hey all

Have done a headgasket change on jdm bug sti, all gone well back up and running, however I've come across a problem.

Been out giving car a run and checking over the vitals I noticed that both left and right avcs advance figures are 0 at idle but only advance to between 3 & 4 degrees throught the rev range.

Everything else is perfect, no running issues, IAM is happy at 16, getting circa 38 degrees ignition advance when toe down but no avcs advance.

Anybody shed any light on it or experienced similar before? Checked and double checked the timing and it's spot on, I'm positive cam sprockets are located correctly and everything else seems happy enough.

I've removed all the screens from the filters on tear down and inspected for damage upon removal, all were in good shape.

Any ideas anyone :brickwall:

Cheers

could be the avcs solenoids, i had to swap one out on my bug sti a while back.

If you are sure the avcs pulley is located on the dowel on the camshaft correctly then as above, possible solenoid sticking or the pulley itself sticking - sometimes a gentle tap with a plastic mallet 'might' free off a sticking AVCS pulley in some cases.
They are easy enough to strip and to clean out the sludge which gets trapped inside - you will be surprised what gets trapped in there, especially after an engine failure and yes, it does get past the screen filters in the banjo bolts.

Thanks for the reply guys.

I believe the solenoid(s) to be fine, I've also used a spare from my own engine which I know to be in good working order.

I will strip and inspect the solenoid housings for any crud and give the pulleys a gentle tap to see if it makes a difference.

Do you know what the standard bug jdm ecu, non mapped should be getting on the avcs advance? Looking around for info but there are varying answers mostly found from across the pond.

Information is being fed back from an ecutek data monitor.

I will double check voltage to the sensors just to be safe, but I'm guessing they are working as I'm getting readings at idle and on boost that vary up to the 4 degrees advance.

Strange how both sides are doing the same, and both are in sync with each other.

Thanks once again for the input tho :thumb:

I honestly wouldn't know what the problem
is but when I had my Bug mapped I was told my AVCS wasn't working due to a dead Neutral Position Switch. RA motorsport and Andy F sorted really quickly. Andy identified this via his software when mapping. It ran perfectly well as far as I was concerned (it was new to me) but noticed the difference once fixed! Apparently it is pretty common on Bugs. Could be worth looking at?????
Rory

as above andy f also said my neutral position switch was a bit iffy but was fine during the mapping and we got a good result.

I can remember reading about such an issue funny enough, wasn't sure if it would cause the effects currently being seen.

Is there a definitive way to test the switch does anybody know? I'll have a browse myself now for the answer but wondered if somebody may chime in with what I'm looking for :lol1:

Another avenue to check, still can't find a solid answer on avcs advance figure :wonder:

I have no idea what to look for but clearly Andy F could see it via his data source and diagnosed it with ease. I did some reading up on it after the event. It's pretty common, cars drive fine but you don't get the assistance from AVCS. I couldn't tell the difference when driving as I had no comparison for the bum dyno prior but after there was little lag in comparison. Me personally would go for a drive and see how it felt (if my car). If it felt laggy I would change NPS as a matter of course but that's just me. I paid about £20 for one from RA off a known good car. I was back on the road 40 minutes later. I know it is always best to find out what is the cause of the issue is rather than just throwing parts at it till you hit lucky but if you can't find out the symptoms to look for or get it checked by a mapper etc I would personally replace this first. Sorry I cannot help more.

What method of removal & refitting were used, the correct holding tool, or using a homemade method ?


Have you driven it under load on the road ?

Hi Paul

I'm guessing you mean removal of cam gears and installation?

Gears were removed using power bar, locking bottom pulley, cam covers removed an cam held with spanner.

They were installed back by lightly nipping up the cam gears first, then installed the belt by lining timing marks up, getting the cams on lobe and held with mini power bar whilst belt slipped on, then again locked bottom pulley and torqued to specs.

Spun engine over a good few times and marks came back Inline with each other.

Yes it has been given load on road which is when we noticed the feedback on the monitor.

Cheers

Thinking about it I can probably find the NPS wires and send it to ground to trick the sensor in to thinking it's always in gear, should eliminate the NPS altogether then I'm guessing, have to try it :wonder::wonder:

So cam held while undone & re torqued up, its not the ideal way to do it, as it can distort the dowel hole in the cam gear, & also load up the avc's internals by not holding the gear with the proper tool.

Yes unfortunately didn't have the correct tool to hand to hold the sprocket.

I can lay my hands on one come Tuesday, so perhaps if after the rest of the trouble shooting comes back with no joy today, I will whip pulleys back of, inspect for any damage to the dowel hole and re torque with correct tool & reset timing again.

Is there a possibility that they need realigning again Paul if it turns out they have been loaded by not using the tool?

Thanks for your replies, much appreciated.

It usually causes issues internally by slightly nipping up or out of alignment of the inner rotor, even with the proper tool this can happen, if your nps is ok, I would slacken off the pulley bolt & re torque with the correct tool, make sure there is oil under the head of the bolt before torqueing up.

Also give it a tap with a plastic mallet as Mick suggested, it all it needs sometimes.

Brill, thanks for all the input everyone, I'll give the above a whirl with the tool should issue not get resolved with the nps switch and cleaning of the housings.

I'll drop pulleys off again at same time and inspect the location hole for any signs of wear or damage should it come to 're visiting the pulleys :) I'll give them a tap first tho just to check.