Taner

Hi all.

Managed to get my project car started yesterday.

It's. A 2008 3.8 in a 996 chassis, anyway. I have an issue.

Can here a loud knocking when the engine is running.

Compressions are all good

Also have rough running feedback and misfires on cylinder 3 according to durametric.

Also bank 1 specified and actual cam angles are way off where they should be on bank 1. Eg should be targeting 17 degrees but it's actually reading -2.5

Any thoughts

StormRune

With the cam reading that far off I would worry that the valves would hit the top of the piston as it approaches top-dead-center. There isn't a lot of clearance built into these engines.

I would expect that would immediately cause catastrophic damage in most cases, but maybe it is kissing just enough to make a sound and not break the piston or valve. I wouldn't run the engine again until you are sure the cams are close to the right position. It sounds like the timing chain is one or more teeth out of position.

Taner

Il pop on the workshop today and re check compressions, plus re log cam angles.

The engine is a variocam plus. I remember reading somewhere that it's possible for the cam to repeatedly knock against its end stops if the oil control pressure to it isn't correct. Is this true or just forum speak.

Macster

Since VarioCam Plus operation is all based on oil flow/pressure any problem with oil pressure or supply can affect the proper VarioCam Plus operation.

Was the engine apart?

If so there has to be some concern that during reassembly something's amiss and oil supply or pressure to one or both VarioCam Plus units is marginal.

If the engine was apart there also has to be some concern that the valve timing is off.

I would hazard a guess valve timing off is the more likely explanation.

I would advise you to avoid running the engine any at all, even turning it over to check compression.

Instead do what you need to do to confirm valve timing is 100% correct. You can have no doubt in your mind after you check this.

If you find valve timing to be correct then you have to suspect oil pressure/supply problems.

If the engine was apart there has to be some concern about the oil pump's performance, any bypass or pressure relief valve perhaps sticking open, or something that is restricting oil flow or pressure to some area/region of the engine.

An oil supply problem to an area/region of an an engine is hard to diagnose. I once encountered what I suspected to be a noisy lifter in a V8 engine I had rebuilt. I ended up removing the intake manifold and the front engine cover and the oil galley plugs and found the automobile engine machine shop had driven the old oil galley plug into the oil galley. During my assembly of the engine I failed to check the oil galley was clear.

As a habit I had done this check for a number of other engines and never found a problem but was in a hurry with this engine and tried to cut corners in a hurry to get the engine back together. Haste makes waste...

Anyhow, I removed the old oil galley plug, resealed the oil galley with a new plug, and installed the front engine cover and installed the intake manifold and the engine fired right with no ticking noise. In fact after the rebuild the engine was so quiet that a few times I tried to start the engine while it was idling. It was that quiet running.

Unless you find a suitable shortcut you may be faced with removing the engine and tearing it down to find the cause of the knocking noise.

Taner

Hi Macster.

Thankyou for your reply, unfortunately the engine has never been apart. It was removed from a running car. Sat in a workshop for approx a year, then put into my car. I'm still on the 3.6 calibration so this may explain the odd valve positions?? Also the O2 sensors are currently disconnected. Need to sort that out as that may also effect the map the car is running off.

I did pop into the workshop earlier and carried out a comp check. All between 270-280 psi.

No clonks or knock when cranking.

Before putting the engine in, I borescoped it, got an oil sample analysed etc. All seemed well

If it has to come out then so be it, but just thought I'd throw it up on here I case others have had a similar issue that was resolved with the engine in situ

Macster

Assuming the engine was not manifesting any issues before then the noise is probably due to the lack of use.

The noise should go away rather quickly after engine engine, assuming of course the engine has the proper amount and type of oil in it.

However, the valve timing reading suggests to me a problem with if not the mechanical valve timing then the VarioCam Plus valve timing control.

This can arise if over time of lack of use a VarioCam Plus seal or o-ring has developed a leak and the valve timing is no longer under control of the DME. That the engine continues to manifest knocking noises suggests an internal engine oil leak.

I may have missed this: Have you dropped the oil filter housing and checked for any signs of say cam chain composite plastic debris or other debris in the filter housing oil and filter element?

But as you noted it could arise from an incompatible DME controller that is unable to deal with the 3.8l engine's VarioCam Plus system.

You'll have to consult with a custom DME manufacturer I guess to determine what role, if any, incompatible DME programming plays in the valve timing.

Taner

Very good point, I've not dropped the filter as yet, I got a sample analysed at work before fitting the engine but that doesn't rule out the breakdown of a plastic runner. Very good suggestion. Il check that out this evening. Will also remove the variocam solenoids while I'm there and check for blockages etc.

As the chassis was a 2003 I believe it should have the correct controller for the vario plus but I have no clue as to what the timing differences are between the 3.6 and 3.8.

I guess I need to search for someone that has taken a dura metric or similar running log at idea measuring desired and actual cam angles for me to compare against the log I took yesterday.

Again, Thankyou for your reply. It's always nice to get another persons thoughts and suggestions

Taner

Right, just been in the workshop again.

Removed both Vario solenoids and both Vario flow Control valves??

The Solenoids seem to function as they should when 12V is applied. they pull the pin inside the housing and hold it firm.

The Control valves however im not too sure about. they move with voltage but only a tiny amount. Surely this isn't right. Its the same with both sides.

On a plus note. there is no sighn of metallic or plastic debris in my filter housing.

Also put the ignition on. 8.8V at Flow valveconnector. 0v at Solenoid connector I assume this will change slightly at idle then again at load





http://s8.photobucket.com/user/TTath...ibrq9.mp4.html





Hmmmmmmmmmmmmmmmmmmmmm

Taner

Is that amount of movement normal???

I though it it would fully expose the oil path holes in each direction???

997_rich

Your video doesn't seem to be working... but the symptoms do sound a whole lot like chain whip or skipped tooth on the timing chain especially given the weird cam angles.

is it easy for you to pull the engine?

I think I'd:

Boroscope(now really cheap on amazon) the cylinders through the plug hole to verify you're not actually impacting the valves. No sense in trashing the engine in the diagnosis process.

Turn the engine by hand and watch with the boroscope to verify proper operation on the failing bank.

Swap sides with the solenoids. See if the problem switches to the other bank.

then I might think about dropping the engine to pull the valve cover. Even if you don't have plastic parts in the oil, the top end chain tensioner can fall off if the retention pin fails. If it falls and gets caught in place it may not get smashed and send plastic parts to the oil pan. That chain slop could give you some bad valve angles or even allow the chain to skip a tooth.

One more stupid question- you have full oil and good oil pressure?

Stupid question #2 is your fuel good? if you have bad fuel and a semi-bad plug or coil maybe the engine is retarding the timing on that bank to try to deal with your crap fuel.

What error codes are you throwing on Durametric? ignition on a specific cylinder?

Taner

Hi rich. Already scoped the engine, found no contact evidence, no scores, no debris. Good oil and lots of pressure.

A mix of crappy and good fuel. Fuel level is low but I have approx 10l of old stale fuel in the tank and 10l of fresh. Il re upload the vid and 2 more pics. Activated and deactivated. Surely no oil can pass through the jokes as they are literally open less than a mm.

Does anyone have a pic of their lift valve

Taner

http://s8.photobucket.com/user/TTath...ibrq9.mp4.html

997_rich

The few rare times that I've actually held one of these in my hand I've never put voltage to it to see how much it opens. It seems very unlikely to me that only the variocam valve is failing out of every part in the whole engine and both of them are failing in the exact same way.

I think I'd go back to swapping them side to side and seeing if the problem switches sides. Also, looking closely at what other error codes you're throwing... I suspect your problem is elsewhere. Are you throwing other codes besides the 02 sensor that isn't in place. Are you throwing codes for cam position sensor? I'd consider swapping sides on that one as well.

good luck!

Taner

Ok strange goings on, since putting it all back together it now runs fine and smooth. Although the knock is still there. The misfire seems to have cured itself.

While together I thought I'd have a little test while it was running.

The knock/tapping is there at idle

Not there at 2.5k plus

Doesn't knock when ramping up and down from 1500 to 4k on and off

Strange.

Thought I'd drop the sump cover to double check the pickup.

Again, all clean and no signs of any broken parts or random objects.



The sound really does now sound like tappers but it I possible to tell what side as the sounds it's so hard to pinpoint.

CrossThread

I am sorry you have ran into a problem, it is always disappointing when you are so close to finishing such a great project like this. You say it was running good, with no noise before it sat for a year? Hopefully it is just mechanical varnish and/or a sticky solenoid that is causing the grief, not something mechanical. Best of luck!