zerMATT951

Ok, so some of you may have been watching my reassembly thread. I'm generally very pleased with my results, but yesterday I started to see a moderate amount of smoke at idle. Chris White warned me that my LR catch can would cause this because of the lack of crankcase vacuum would push oil out through the turbo seals so I immediately thought "easy fix". Not so much.

When I got home tonight, I cobbled together some hoses to re-route my AOS port back to the MAF pipe. The problem still exists. I had to use a hose section that has a minimum ID of about 1/2", is that too small for a temporary test?

The engine wasn't smoking like this before I blew the head gasket (5 years ago), the head is a fresh rebuild (5 years ago, been sitting on a shelf), the K26/6 is a fresh rebuild from Lindsey Racing.

What should I look at next? 3/4" vent hose? Compression/leak down test? Check plugs?

I searched and found a few threads on the subject, and it sounds like adding crankcase vacuum back to the mix should solve the problem, but it doesn't... Help!

Crackership

I responded to your other thread, but is the smoke blue? black? Is it just on idle and decel or does it happen when your on it too? I know it's hard to tell... you may have to have someone drive behind you to look...

blown 944

give it a little time with the AOS hooked back up, Make sure it is actually getting some vacuum too. I have had more trouble trying to eliminate the aos vent and have certainly learned.

If you really want to find out if it is the turbo you can check the whole airflow tract and determine where its from. I would suspect that you will only see oil in the downpipe

zerMATT951

Dave, it's definitely oil, and it goes away once I'm cruising again. It starts puffing soon after I lift and roll to a stop at traffic lights, pulling into the garage, etc. It doesn't smoke on startup, but I haven't done a cold startup and watched it for any period of time either. It's safe to say that I've got to drive it for a bit first, or at least let it warm up for a few minutes before it starts to smoke. I do get some black smoke under boost, which I think is fuel and unrelated. My wife says it stinks when she was behind me and I did a hard 2nd to 3rd pull, and it wasn't smoking, just raw fuel and I'll deal with that issue after I get the oil smoke figured out.

Sid, I'm not at the point yet where I want to disconnect any turbo pipes, but I may at least try to eliminate oil sources before turbo hot side like looking inside the IC pipes, check plugs, etc. I'm also going to go ahead and pull off the smaller temporary hoses that I connected to the AOS and come up with something better that maintains 3/4 all the way. I am also going to compare vacuum at the dipstick vs the tree pipe to make sure the AOS isnt clogged or something else isn't preventing crankcase vacuum. I thoroughly cleaned the AOS while I had it out, and I know it was all wide open when I put it back in.

Clown

I hope you can get to the bottom of this because I have the exact same problem with my car and have been spending the past few months trying to research and figure out what is causing this. I just put my car back together a few months ago and same thing smoke at idle and only idle. Very embarrassing at a red light and I pray for green lights the whole way to the grocery store. It does not smoke at cold startup but if you let it warm up for several minutes in the driveway or drive it for a mile and then stop and idle the smoke starts coming out. Start driving and it goes away. The general consensus was that the turbo seals were leaking. Well I just pulled the turbo two weeks ago and did not see any oil on the hot side. I sent it off any way to get rebuilt but the turbo builder said that the seal were still good and did not see any oil inside. I put the turbo back in the car but waiting on an M-Tune order to arrive so I can start the car back up. Hopefully I will have the M-Tune early next week so I can fire it up. While I was at it, I replaced the plugs, ignition wires, O2 sensor and changed the oil to non-synthetic. I will keep you posted on the results but I have a feeling that it is going to smoke regardless of the above mentioned changes. If it is still smoking I will probably pull the head and replace it or have it rebuilt since I was told the smoke could be caused by worn valve seals.

One thing that is strange about my situation is that when I put the stock exhaust back on with the cat for emission testing a week or two after my rebuild, I did not have any smoke while the stock exhaust was on. After emissions I put the cat-less 3" exhaust back on and it started smoking again at idle. Apparently whatever is smoking was being burned off by the cat.

Does your car have a cat-less exhaust on it? Do you use synthetic oil? Has the O2 sensor ever been changed on that 25 year old car? Keep us posted...

zerMATT951

My head is fresh with new seals and guides, I have new plugs, wires, and I don't use synthetic oil. I have no cat, but I drove the car without a cat for 5k miles before the HG blew prompting this "rebuild", there was no smoke. I have no clue about the O2 sensor, but I can't imagine that would have much to do with oil smoke.

My car is doing exactly as you describe at the start of your first paragraph. It's quite embarrassing because I spend quite a bit of time sitting at red lights...

Are you running a stock AOS with the vent tube run back to the turbo inlet tree pipe?

Rob

Look at the bottom of the connection between the turbo center housing and the turbine housing and see if it looks oily and leaking there. If so, your turbo is leaking oil out the rear turbo seal. Also, IIRC you modified the top of your AOS and removed factory restrictor. Maybe you can come up with something that takes the larger size opening at the top back down to the 6mm diameter and see if that helps.

Crackership

I'm sorry you're having this problem, Matt... I hate to say this, but I've been told that a new or freshly rebuilt head will exacerbate any problems the block has... I had a similar experience with my Alfa... It didn't have any real issues, except it was slow, so I bought a set of Glenwood Motors heads, cams, headers and a GoTech standalone... put it all back together, and while it was faster, it also blew a smoke screen worthy of 007... Everyone I've talked to about it seems to think that the new heads turned what was minor blow-by into a major oil burn. I hope that's not what's happening to you.

It is worth noting, however, that when it comes to engines, the GTV6 and 944 engines are similar in that they are both 2.5L and operate on the principle of internal combustion... but beyond that, the similarities become harder and harder to find... the Alfa is a wet-sleeve block... and it has what I can only describe as metal golf tees as a key component of the valve train... and there's a sense of deliberateness with the 944 engine, where the Alfa engine kinda looks like it was put together by someone who was on vacation that day...

Clown

I am running a Stock AOS and I do run it to the MAF tree. I have never inspected it though. I wonder if a bad one would cause smoke?

I guess between the two of us we have just about checked everything. I was hoping you had an old head on there as well....how depressing I was beginning to think that is my problem but now I dont know.

Someone told me one time that they had a bad O2 sensor that was causing smoke. They replaced it and no more smoke.....Beleive me I am trying to eliminate all possiblilites hence new spark plugs wires, o2 sensor, rebuilt turbo. ....I am off to research AOS to see if that is a possiblility...KEEP ME POSTED as I beleive we more than likely have the same problem. Seems like you have more leverage on this forum as I am a new guy around here....hopefully we will get to the bottom of this.

Jfrahm

If one or more of the rings are in upside down it might behave as you describe.

zerMATT951

I'll see if I can see that far up from under the car when I have it up in the air again. Hopefully the seals aren't leaking on a fresh rebuild!

I've currently got the AOS re-router to the MAF tree with a size restriction between 1/2 and 3/8, so I don't think going down in size is the answer. I'm going to try 3/4 all the way through and see if that makes a difference.

I've heard of that happening too, but I just changed my oil and opened the drain on the catch can and it's bone dry. If I had major blow-by, I expect I'd have got some oil out of it. I also did a compression test and they are all even with a 141 psi average. I don't have a leak-down gauge, but an empty catch can and good compression should equal decent rings.

I can see that issue with fuel (black) smoke, but not oil smoke. The O2 sensor helps the ECU calculate AFR's, so if it's bad, it could feed too much fuel causing a rich condition.

Agree, but I stopped short of engine internals on my rebuild because the rod bearings and pan gasket had been replaced 6,000 miles ago. A compression test today also looks good (see below).


1,000th post!!

zerMATT951

Pulled the plugs, they look ok other than signs of being a little rich. I guess it's time to get my WBO2 hooked up.

Compression test looks good too with an even spread and 141 psi average.

I also just changed the oil... maybe it was over full? I'm going to make sure I stop just a bit short of completely full.

C ANDERSON

Add me to the list of ones doing exactly the same thing, did it before adding the catch can. never got oil in the can either. compression was a little down but not bad. turbo was recently rebuilt K26-8 4" exhaust , maf . went back to maf tree from aos and still smoked. Just completing a new engine build with new turbo so will report soon not back in car yet. The old cylinders had some wear at top and a few small scratches just doen't add up the way and times it smokes . This one could be run on the track with no smoke but consumed oil more than normal . Also no oil ever found in IC pipes and after pulling turbo no signs of oil in hot side , could it be burning it so fast that it never builds up there ? Think maybe they don't smoke until the pipes get hot enough ?

Clifton

zerMATT951

I'm baffled, and I'm not alone. Surely someone has seen and solved this problem before, we need to keep this thread alive for a while so that we get more input...

And I'm changing the name of the thread to remove the word "decel" because I think that is throwing some people. It's really only an idle issue whether I'm decelerating or just stopped sitting at a light.

Clown

Yes I agree we need to get to the bottom of this smoke at idle issue and keep this post alive !!!

I would like to see some video of your cars smoking to see if it looks similar to mine. I have some video of mine but need to post it on Youtube so I can give you guys a link. May be we could all post a short video. Also if you could rev the engine in the video to see how it changes the smoke under vacuum.

There are other threads in this forum with people who indicate similar problems but there never is an answer posted or a "I finally figured out why its smoking" post at the end...

I will try to post the video soon....