WEIRD idle issue on turbobrick

So as some know, I've been driving the 940 wagon bought from JD for the past year or so. It's been great, but now that my kids are starting to reach the 'don't have to be within 3 feet at all times' age, I have noticed something odd. Every once in a while, at idle only, the car will absolutely belch blue smoke. And then stop. Seriously. Cracking the throttle gets it to stop too (reduction in vacuum, I would guess) but it doesn't start again when you close the throttle again. The vacuum gauge looks normal the whole time. The car doesn't use any oil now with the new PCV system. This is seriously weirding me out. I got a bunch of crickets over on turbobricks. Now it's time for the best and the brightest to tackle it.

And yes, LS1 is a potential answer. The wife is away this weekend.

Well, the obvious things would be to check for oil not draining back out of the head. Pull the valve cover and see what you find. If there's something blocking the drainback holes, that could be the issue.

PCV system, put an oil catch can on there, check your breather filter if you have one, you may be collecting oil in one of your PCV lines and then you're having to 'purge' it, a can would help, OR you can increase the size of your lines, OR you can check for kinks, bends, etc, i'd pull your PCV lines and inspect for oil...

http://www.srtforums.com/forums/f70/blue-smoke-idle-fix-thank-you-ben-522951/

You'll find almost all of them have oil leaks in the turbo. The oil goes to the intercooler and sits there, in a pool, at the bottom. Every once in a while some gets sucked up into the engine, producing a nice cloud.

Really want to surprise yourself? Pull the intercooler out and check. It's easy to do. You'll be amazed at the amount of oil that pours out.

foxtrapper wrote: You'll find almost all of them have oil leaks in the turbo. The oil goes to the intercooler and sits there, in a pool, at the bottom. Every once in a while some gets sucked up into the engine, producing a nice cloud. Really want to surprise yourself? Pull the intercooler out and check. It's easy to do. You'll be amazed at the amount of oil that pours out.

None.

Just did it.

Perhaps the PCV can gets full somehow, spits the excess into the intake, and then its fine? No idea why it would do that though. Sure its not actually running rich? What does the AFR do when this happens? How do the plugs look?

The turbo drain lines are knows to get clogged on those-perhaps its backing up into the turbo momentarily?

Plugs look fine - afr looks fine the whole time... interesting thought about the turbo...

Mikey52_1 wrote: Well, the obvious things would be to check for oil not draining back out of the head. Pull the valve cover and see what you find. If there's something blocking the drainback holes, that could be the issue.

Just at idle? Cracking the throttle makes it go away? Doesn't sound like it fits...

Raze wrote: PCV system, put an oil catch can on there, check your breather filter if you have one, you may be collecting oil in one of your PCV lines and then you're having to 'purge' it, a can would help, OR you can increase the size of your lines, OR you can check for kinks, bends, etc, i'd pull your PCV lines and inspect for oil... http://www.srtforums.com/forums/f70/blue-smoke-idle-fix-thank-you-ben-522951/

All of the pcv stuff was swapped a few months ago - no changes to this issue.

Well ok, now we must think!

I agree with you, vacuum is likely in play. At idle you get your 2nd highest vacuum. 1st highest is decelerating the engine. But that deceleration condition is mighty transient, and might not induce the smoking.

Intake valve guide is a likely culprit, but it doesn't fit neatly. High vacuum pulling oil past a worn guide and or seal.
Why sporatically though? Hmmm, it's a valve under bucket setup. They pool oil as I recall. Might be related.

Might want to also do a quick balloon check on the PCV, just to make darn sure it really is working right. Pull the dip stick, put a balloon over the tube, and watch to see if it inflates. Since you've replaced everything, it probably won't. But it will let you see if there's any strange transient puffs of pressure in the crankcase.

I know the older Volvo turbos (740 specifically) had issues with the oil drain back tubes clogging (I don't think they had water cooled center sections) from coked oil. This could cause oil to get past the seals in the turbo and cause issues like this.

The solution was to clean the oil drain back thoroughly, then use good synthetic oils, proper oil change intervals and let the turbo cool a bit before shutting down to prevent it happening as frequently.

Not sure if the newer turbo's had similar problems or not.

Just a thought.

foxtrapper wrote: Well ok, now we must think! I agree with you, vacuum is likely in play. At idle you get your 2nd highest vacuum. 1st highest is decelerating the engine. But that deceleration condition is mighty transient, and might not induce the smoking. Intake valve guide is a likely culprit, but it doesn't fit neatly. High vacuum pulling oil past a worn guide and or seal. Why sporatically though? Hmmm, it's a valve under bucket setup. They pool oil as I recall. Might be related. Might want to also do a quick balloon check on the PCV, just to make darn sure it really is working right. Pull the dip stick, put a balloon over the tube, and watch to see if it inflates. Since you've replaced everything, it probably won't. But it will let you see if there's any strange transient puffs of pressure in the crankcase.

I have done something very much close to that, the valve cover fill cap on these things is the right weight where you can let it sit unscrewed on the cover (1/2 turn thingie) and if it bobbles around or flies off you need a new PCV system (which is very odd in turbo brick land) which is what I found and what I fixed. It no longer does that. The symptom that I was chasing then was that the car would belch blue smoke whenever I closed the throttle under boost. That's totally gone now, as I found LOTS of leaks and crappy fixes (ever see a smaller vacuum hose slid inside a larger vacuum hose and clamped at either end?) within the PCV system.

Boy, I hate to say it, but a valve guide does sound interesting. The oil pump shouldn't be doing a whole lot at idle, though, I'll have to find out if something is plugged in the drain as you mentioned. If it were more intermittent (every 30 seconds, every 1 minute) I would buy this, but it's like once per week for a few minutes as long as I stay at idle. Also, the fact that it clears up if I crack the throttle, even after the throttle is closed again makes me doubt this theory, because the hypothetical pool of oil would not only still be there, but be bigger. If seems as if that would cause it to belch oil even more instead of clearing up.

Oh well, if I have to pull the head I may as well stick a 302 in there, right?

Ugh...

turboswede wrote: I know the older Volvo turbos (740 specifically) had issues with the oil drain back tubes clogging (I don't think they had water cooled center sections) from coked oil. This could cause oil to get past the seals in the turbo and cause issues like this. The solution was to clean the oil drain back thoroughly, then use good synthetic oils, proper oil change intervals and let the turbo cool a bit before shutting down to prevent it happening as frequently. Not sure if the newer turbo's had similar problems or not. Just a thought.

I always use a good synthetic, with 5K changes, and I know JD did too. I still may have an issue, though, the car is near 20 years old and has 230k on it. I'll look into checking the oil drainback from the turbo. I am not exactly sure how that works anyway, and you never really know until you break it when taking it apart, right?

foxtrapper wrote: You'll find almost all of them have oil leaks in the turbo. The oil goes to the intercooler and sits there, in a pool, at the bottom. Every once in a while some gets sucked up into the engine, producing a nice cloud. Really want to surprise yourself? Pull the intercooler out and check. It's easy to do. You'll be amazed at the amount of oil that pours out.

I was actually really hoping a ton of oil was in there, too, it would have been a great excuse to get a bigger turbo.

tuna55 wrote: Oh well, if I have to pull the head I may as well stick a 302 in there, right?

Or a 16v head.

m4ff3w wrote:

tuna55 wrote: Oh well, if I have to pull the head I may as well stick a 302 in there, right?

Or a 16v head.

Or maybe a LSx...

tuna55 wrote: And yes, LS1 is a potential answer. The wife is away this weekend.

tuna55 wrote:

tuna55 wrote: And yes, LS1 is a potential answer. The wife is away this weekend.

Like I said,

If it's like my 740 at all...the oil drain tube should be relatively simple to get to with a smattering of extensions and sockets (maybe a swivel or two) and the car up on ramps.

I think mine had two bolts on the holding it to the turbo and it slip-fits into the block. I don't recall if there was a bracket stabilizing it anywhere along the way (though that is likely).

Clem

There ya go, a 302 will fix everything!

I'm not happy with the valve guide theory either, for exactly the same reasons. It should continue for several seconds after you crack the throttle, not instantly stop. And it should always leak some, so you should be seeing oil consumption, yet you say it's not burning oil any longer.

Hmmm, any unusual roughness to the engine when it does this? Anything else that could help diagnose or provide clues?

In wondering if we/you are chasing a red herring, a couple of thoughts:

A a fuel injector hanging a bit. At idle with the manifold vacuum high injector pressure is at its lowest. The smoking wouldn't be oil, it would be gasoline. A slightly damaged injector could occassionally go just out of spec at idle enough to not send a good burnable mixture to the cylinder, and leave it to burn in the exhaust manifold or cat. A blip on the throttle brings the pressure right up, and the injector then behaves fine. Yea I know, it's a reach.

Throttle body. God knows why but on the Volvo's especially those engines, they are hyper sensitive to the throttle plate being clean, or they go all weird at idle. I've never heard of one smoking because of it, and I can't see how it could do it. But its easy to clean with a rag and take that one out of the equation.

At true idle, the throttle position sensor is telling the ecu the engine is idling. That has the computer in one mode. The faintest touch of the foot on the pedal changes that switch position and the computer mode. Could there be something here that we're not thinking of?

foxtrapper wrote: There ya go, a 302 will fix everything! I'm not happy with the valve guide theory either, for exactly the same reasons. It should continue for several seconds after you crack the throttle, not instantly stop. And it should always leak some, so you should be seeing oil consumption, yet you say it's not burning oil any longer. Hmmm, any unusual roughness to the engine when it does this? Anything else that could help diagnose or provide clues? In wondering if we/you are chasing a red herring, a couple of thoughts: A a fuel injector hanging a bit. At idle with the manifold vacuum high injector pressure is at its lowest. The smoking wouldn't be oil, it would be gasoline. A slightly damaged injector could occassionally go just out of spec at idle enough to not send a good burnable mixture to the cylinder, and leave it to burn in the exhaust manifold or cat. A blip on the throttle brings the pressure right up, and the injector then behaves fine. Yea I know, it's a reach. Throttle body. God knows why but on the Volvo's especially those engines, they are hyper sensitive to the throttle plate being clean, or they go all weird at idle. I've never heard of one smoking because of it, and I can't see how it could do it. But its easy to clean with a rag and take that one out of the equation. At true idle, the throttle position sensor is telling the ecu the engine is idling. That has the computer in one mode. The faintest touch of the foot on the pedal changes that switch position and the computer mode. Could there be something here that we're not thinking of?

No roughness at all, and the afr shows that everything is fine. Now, it could be wrong, but I would bet that if an injector went honky, that it would show as rich (good theory, though). Interesting idea about the throttle body. I will try that.

As far as 'idle mode' it has an IAC which works on PWM 12Vdc and I am not entirely sure how it acts when you're off the gas vs on the gas. It may, as you suggest, go full closed when the throttle is cracked. If the idle speed were going wonky at the same time, I could totally buy this theory. I have had the IAC off and it operated great when placed on straight 12Vdc off and on.

If its a significant amount of smoke, like you can fog for mosquitos, you'll probably be buying a turbocharger soon.

I keep thinking turbo as well.

Those PWM IACs are supposed to close under acceleration IIRC.

I'd like to blame the turbo as well. And initially that's where I pointed. But he pulled the intercooler and it was clean inside. And I can't think of any reason it would smoke at idle, and instantly clear with a blip of the throttle if the turbo was leaking.

Looking again at the initial post, you say it will occassionally give a big belch of blue smoke. As in like it just took a big gulp of oil? Interesting, I'm sure that's a clue. And does it clear on its own, or will it only stop if you blip the throttle? Hmm.

Are there any fluids you're having to top off? Or other weirdness that perhaps we could draw together? A brake master cylinder leaking through booster, a blown head gasket, etc.

I don't remember about the 940's but the 240 & 740 turbos didn't have a flame trap in the pcv system. They had the hose, but not the trap. The turbo served as the trap. If you put a flame trap (the perforated plastic round thing) in the system, it would plug and the turbo seals would leak. I was going to ask another senior citizen here what he remembers, but he forgot to come in to work today :)