Hi Guys,

I'm a bit stumped with my 1997 Civic (D16Y7) that I just did some work on. It started smoking after sitting for a couple of months while I did an extensive overhaul of the suspension and engine. A basic overview of what I did to the engine:

New timing belt, water pump and drive belts (Gates)
New valve stem seals (Enginetech)
Valve cover gasket replacement (Fel Pro)
Oil pan gasket replacement (Fel Pro)
Valve adjustment
Replaced plug wires and spark plugs (NGK)
Replaced the fuel lines (Lines To Go)

A little history of the car: I got it at 239,000 miles and it's now at 298. I did a compression test when I got it and got 185-195 psi across the cylinders. I've generally kept up with maintenance, including oil changes and valve adjustments. It has a history of using oil (mostly leaks) and smoking significantly at start up. That is what prompted me to replace the valve seals. The timing belt was done shortly before I got the car so I was a little ahead of schedule there. It had no history of smoking under acceleration or in any significant amount after about 30 seconds of running.

So after I finished the work, I started the car and immediately it started smoking. It smokes noticeably but not significantly at idle, increasing steadily with increased RPM. It does not taper off as the engine warms. As far as I can tell it does not smell like coolant or raw fuel. I have opened up the throttle body and found oil pooled in the intake manifold. If I clean the oil out, the car smokes less at first, but then it increases back to the same amount as before after a minute or so of running. Some amount of oil then reappears in the manifold.

What I've done to troubleshoot:

Confirmed the timing is correct: It is
Compression test: 185-195 across the cylinders-the same as when I got the car
Cleaned and checked the PCV valve
Checked coolant: No obvious loss of coolant and no oil in the coolant or vice versa
Pulled the spark plugs: All were sooty, but only #2 cylinder looked even a little oily
Checked the oil level: Normal. I had to add a little more than usual (about exactly 4 quarts) BUT I cleaned the oil pan so I imagine that has something to do with it.

I doubt it's the rings because as I said, this is a new and very sudden problem and the compression hasn't changed. I have not done a leak down test but that may be the next step. As far as the headgasket, I am more willing to believe it would fail suddenly but that doesn't explain why the compression is normal (for this engine). Is it possible there's a small headgasket leak that could produce that much smoke? The main suspect in my mind is the valve seals. But I feel confident that I seated them correctly. I did have trouble getting the old seals out. I think I scratched one of the valve guides on the vertical surface but it was below where the lip of the valve seal rests. It also seems like a ton of smoke for it to be the valve seals. Here is a link to a video of the car running and the smoke it is producing:


Of course I am willing to be corrected. As far as the valve adjustment, I've done them before on this and other engines so I doubt I screwed it up that badly. Would it even be possible for a bad valve adjustment to lead to this amount of smoke?

A few additional notes: The car seems loud, especially inside the cabin where I can feel the vibration of the engine much more than before. I haven’t tried to troubleshoot the problem because I figure whatever is going on with the smoke could be making the engine run rough and if I fix the smoke and it still seems loud and vibrates a lot I can deal with that as a separate issue. I am trying not to go down the rabbit hole or chase my tail excessively. I also did change most of the motor mounts. I'd be really grateful for some help, I don't have enough experience with this engine to really know what the possibilities are and if I proceed on my own I'll basically be just guessing, which is not a good place to be with troubleshooting.

 

When you say you changed motor mounts, did you stick with OEM or did you switch to a poly bushing mount setup?

 

They are an OEM equivalent. I do think the new mounts could account for the new "feel" of the motor from inside the car. I got a leak down test kit today so that is my next step as far as troubleshooting the smoke. I put the car back together and took it for a drive. If anything it feels better than before, plenty of power, no hesitation accelerating. I'm a little baffled but will report back when I've done the leak down test.

 

Well for anyone interested in this case, I conducted a leak down test and unsurprisingly it revealed nothing new except that the engine is in excellent condition (ESPECIALLY for nearly 300k) so I'm going to proceed on the assumption that it's the valve seals and get OEM seals and install them next week. I'll also look at the seals I installed and take some measurements and inspect the valve guides to make sure they're not damaged and to try and determine whether I had the seals seated properly.

One final question before I do that. Is there any chance a bad or contaminated catalytic converter could be causing smoke? Like if some oil leaked into the exhaust while changing the seals the first time? I suspect the cat is bad or at least in poor condition and it has an ugly crack where the upper O2 sensor is installed so it's due for replacement anyways. It is also occasionally throwing a code for the downstream O2 sensor. I don't know how much oil would have to leak into it to produce the smoke I'm seeing but I'm still struggling a little with new valve seals leaking that badly...

 

I would highly suspect the seals to be causing your smoking. Also wouldn't you think it's possible if your seals were leaking, oil is getting into the cylinders and causing smoke and also the blow by of oily smoke going into the pcv valve and in to your intake manifold..? Could try using super tech seals- I've always had good luck with them but also can't go wrong using oem..
Your catalytic converter could be causing some smoke...that thing gets super hot and possibly the oil is getting into the exhaust burning up.. just my thinking of possibilities..

 

Yeah I suspect the oil appearing in the intake manifold was either leaking down from the intake valve seals or residual from the replacement process. After cleaning it out a few times it seems to have stopped, while the smoking has continued. As far as it goes, it's not that hard to redo the seals and the OE parts are only $30 or so. By process of elimination it's the most likely thing to be causing the smoke so I'm willing to take the risk of doing the work over. Since I'm not worried about damaging the cat I'll probably take it out on the highway and just make sure it doesn't stop smoking after running the car for a while. Unlikely to work but it's free to try...