Exhaust Smoke On Start-Up

[PNWingnut]

I've got a 1984 Eagle wagon that I purchased a bit over a year ago and has an issue with the engine smoking when starting from cold. When starting up the car from cold it runs pretty rough and sounds like it isn't firing on all 6 cylinders. I have to give it gas for a minute or two before it will idle normally, all the while blowing out oil-smelling smoke. It leaves an oil stain on the ground where the exhaust comes out. Once the engine is warm, it's fine. Starting the car again after stopping for errands, it's fine.

I'm quite confident the issue is not related to the cylinder head. I had the head worked on not too long after getting it. They resurfaced it, re-ground the valves, replaced several valves, and replaced all the seals. The issue remained the same after that work. I've also replaced the head gasket and replaced the plastic valve cover with a metal one. I've also checked the compression a couple times and it is (to my understanding) normal, between 150 and 170, which has me scratching my head. I took a peek, inside when getting work on the head done and the cylinder walls did not look bad, but I didn't do anything more than that. There was a decent amount of carbon build up on the pistons, but not too surprising with the issues I'm having.

My current thinking is that the head needed work and oil got in which caused carbon buildup which caused the rings to get stuck which is now causing the issue even with the head re-machined. I recently put Marvel Mystery Oil in each of the cylinders, let it sit for a couple days (turning the engine every so often), then once it drained through I planned to drive the #$*& out of it to try and break down the (supposed) carbon build up, free my rings, and get this issue solved. Currently, the car is in the shop getting steering and suspension parts replaced, so I haven't driven it much since putting the MMO in.

For those more experienced than I, does my thinking sound correct? Am I missing something or wasting my time? Should I just tear down the engine and see the rings for myself? I will be moving in August and want to have this issue fixed before then, so I only have so long to get this figured out. If it is relevant, the emissions stuff was removed by a previous owner.

Thank you very much,
Blake.

[89 MJ]

If you hold the engine at part throttle and then dribble tiny amounts of automatic transmission fluid or water down the carb, those will be the best way that I've heard of to free up the rings and clean out the engine.

[MIPS]

When I had a head renewed in 2020 it had similar issues of coughing oil on a cold start (left to sit) and while they did the valve seals they did not do the valve guides. When it was rebuilt again in 2022 they found the guides were badly worn and it should of had the valves changed at the same time previous. This was causing oil to run down the guides even with new seals and leave oil and a LOT of carbon in the cylinder.

[Ludworks]

I wouldn't tear it all down just yet. Your logic is sound, but if the rings were so stuck or damaged that you're sucking enough oil past the pistons to blow it out the exhaust I'd expect that thing to be clattering like a diesel on startup.

Mips is right that worn valve guides can cause this issue. The valves can "wobble" in the guides and let oil past, but I would expect to see at least some change with new stem seals, especially since the shop apparently checked and replaced several valves. The fact that there is no change is mighty suspicious.

I'd recommend you take it for a drive, burn off all the oil that's on the pistons, maybe dribble some water in the intake like 89 MJ suggests, then let it sit overnight. In the morning pull the spark plugs and take a look down the spark plug holes. Rotate the engine by hand to bring the pistons up to a good viewing height. If the pistons are oily it's definitely a head issue. Take a look at the plugs too and you'll be able to tell which cylinders are getting oiled, that should narrow things down substantially.

Also, maybe check the PCV system. Make sure it's routed and functioning correctly. Pull the line from the valve cover and see how much vapor is coming out of your crankcase while running. If you're sucking oil up past the rings it stands to reason you'd be pushing some exhaust down past them too.

[PNWingnut]

Alright, I've got a bit of an update. I got the car back from the shop yesterday (yay!) and took it out for a good long drive to burn off the oil. This morning I took off all the spark plugs and took a look inside as suggested. The spark plugs were all dry and the pistons looked pretty dry as well. I did see one drop of something on #2 and I couldn't really see into #6 just because of how far back it is plus the wiring harness in the way. Otherwise, all dry and I would think if that was causing the amount of oil that blows out the exhaust to happen I'd see more than 1 singular drop.

I also checked the PCV hose and did find that there was a hole in the hose. I replaced it and checked that I have suction at the PCV valve while it's running, which I do. While checking the PCV valve suction after changing the hose I verified that yes, it is still blowing oil out the back.

I took off the top of the air cleaner to watch where the vent from the rear of the valve cover connects to it. When I give it gas I see puffs of exhaust smoke come out and there is some oily residue there in the air cleaner. Am I correct that this sounds like blowby?

I have not yet dribbled water into the intake, but will probably be trying that soon.

[Ludworks]

I would also expect, with a cracked head or worn valve guides, that you'd see more than one drop of (possibly) oil on one piston.

I'd also think that if you had a PCV issue you'd see a lot more oil in the air cleaner. MIPS had some fun with that a few years ago, he might have some insights.

Were the spark plugs fouled or did they have that nice lightly-toasted marshmallow look to the ceramic? With oil in the combustion chamber you'd absolutely see one or more spark plugs covered in ash and/or black gunk.

Crazy question here, but are you sure it's oil? I just recently saw where a rich condition caused black liquid mist to spray out the exhaust. It wasn't oil, but a mix of water, un-burned gas, soot, hydrocarbons, etc. It makes a pretty convincing "oil stain" where it speckles the concrete (and your shoes) but it's actually just too much fuel. It also can have a pretty strong smell. Not so common to physically see that with a working catalytic converter, but it could happen and would explain the rough start condition when cold. You'd see a lot of white/tan exhaust as opposed to the bluish smoke of burning oil.

[PNWingnut]

I think we are progressing in the right direction!

None of the spark plugs were fouled, the ends did have that toasted marshmallow color on the end and were dry.

I took a look at the carburetor and that was certainly part of the issue. What I forgot is that before I got the head worked on I had to turn the idle screw out a lot to get it to idle for me. But after getting that work done I did not adjust it back, so it was still 4+ turns out. I set it back to 1.5 turns and checked the two mixture screws at the base of the carburetor as well (they were fine).

As for the smell, I have a hard time telling what it is, but I'll give it another whiff next time I drive it. With the screws adjusted I started it up and immediately I noticed a better startup. Much less rough and didn't have to give it much gas to keep it running. I then took it for a drive on the highway to try and clear things out again. I am heading out of town for a couple days, but when I get back I'm going to start it up again, give the carburetor the tuning it needs and see where we are at. I may also do another compression test.

As a side note, I have a Holley Sniper EFI on the way, but I want to figure out this issue first. I'd rather spend time futzing with the carburetor and getting the exhaust smoke gone as is before adding something new into the mix.

[Ludworks]

Very good!

You should see less and less of that oily fluid as it works out of the exhaust. Another long drive will help. I'd suggest an oil change once you're happy with the carb. With that much extra fuel there's probably some in the oil.

Unfortunately if you've still got a catalytic converter it's probably shot...but I'd say most cars of that age have the same issue, so par for the course.

Modern gas smells sort of vaguely sweet and a little like alcohol, though it varies a bit being rich or lean. Some people like the smell.
 
Burning oil is thick, acrid, and sort of plasticy. Nobody likes it. You'll taste it and feel it on your tongue if you get a big whiff.

[89 MJ]

Glad you've made such great progress on this issue.

[PNWingnut]

I just completed a compression test on the Eagle. #1 - 135psi, #2 - 140psi, #3 - 145psi, #4 - 145psi, #5 - 140 psi, #6 - 150psi. (I rounded to the nearest 5 since my dial doesn't have 1-digit tick marks) From a quick Google search it sounds like factory compression for the 258 was 120-150psi with a max variation of 30psi, meaning my compression is good.

I did get a compression test done about a year ago and had higher numbers: #1 - 160psi, #2 - 157psi, #3 - 165psi, #4 - 166psi, #5 - 174, #6 - 170. However, that was from a shop that I didn't have much trust in. After taking it in they basically shrugged their shoulders at me. This was before having the cylinder head machined and before I had to exhaust replaced to fix multiple leaks (and get a nice muffler). So even though I don't know how you can mess up a compression test, I still don't have much faith in it. Also since I've made impactful changes since.

I think at this point I'm going to move on to installing the EFI. All the pointers and help has been very much appreciated.

[Ludworks]

I think your numbers look just fine and point to reasonably healthy rings.

This forum is a great place to find help. Lot's of members have done EFI so if you need help with that you can find it here too.

Good luck!