'94 MM 2.4 white smoke

Hello all, looking for some advice on my '94 MM 2.4. Over the past couple of weeks it has started to develop an issue. At first intermittent but now happening most of the time. Truck has 126k on the clock and is in otherwise amazing shape.

The symptoms:

- The engine will sometimes idle up. No tach on this truck, but it feels like it picks up a couple hundred RPM.
- Seeing white smoke with a hint of blue as the white dissipates at idle, spitting some liquid as well. Seems to be water, doesn't stain the concrete.
- Runs like a top, strong acceleration, no stumbling and no lights or anything.
- It only has about 100 miles since its last oil change (the smoke started happening just prior).
- No telltale coolant issues that I can see. Maybe some slight cloudiness in the overflow tank but nothing decisive.

Here's what I've tried so far:

- Pulled the plugs to look at condition. 2, 3, and 4 are a little cleaner than 1 but all of them have only been in about 1500 miles so I'm not sure how much that means.
- Checked the vacuum lines for leaks with carb spray, no dice.
- Looked for oil sludge buildup on the cap, looks really clean but again the oil has maybe 100 miles on it.
- No sign of oil in the coolant.
- I topped off the coolant to the full line to see for sure if it's getting consumed. The truck has only run for a few minutes since then, not sure yet.
- Pulled the radiator cap and ran the engine while cold. No bubbles in the radiator after a minute or two idling.
- Replaced the PCV valve as it was a little sticky, no change.

Some of this feels like the early stage of a head gasket, but it doesn't feel 100% like that to me. I'm far from a pro, hoping someone here can point me in the right direction. Could this be an intake gasket? I taught my nephew to drive stick in this truck and he had it bucking around a lot. Maybe that put stress on the 28 year old gasket?

Just trying to rule everything else out before the head has to come off. Thanks in advance for taking a look!

Sometimes a failed head gasket or cracked head doesn't result in coolant finding it's way into the oil galleries. White smoke is usually a symptom of coolant in the combustion chambers. The spark plugs being scoured clean of carbon deposits would also indicate this. It doesn't necessarily need to pull coolant at a noticeable rate for it to be leaking. There is a coolant test kit you can buy that will react to the coolant if there's a combustion chamber breach but I would try re-torquing the head bolts or at least checking head bolt torque first. Avoid an engine overheat scenario at all costs. The 4G64 head can be temperamental and has been known to warp enough to cause the cam to seize in the journals and snap - not good. I'm going to doubt that the intake manifold gasket is the culprit but weirder things have happened...

http://www.mightyram50.net/vbulletin...a-tint-of-blue

Blue/black smoke on acceleration from a standing start/idle may be bad valve stem seals. It usually clears quickly once you're rolling and might show up again under heavy load like accelerating up an incline. If the valve stem seals are shot, the spark plugs will foul from oil contamination and you will see traces of it on the backs of the valves along with a build up of moist looking crud.

Thanks all for the help! I do pay attention to the temp gauge and there haven't been any overheating issues since I've owned the truck (about a year and 3000 miles now). It sometimes will make a small puff of blue smoke on startup if it's been sitting a few days but I wrote that off as typical old Mitsubishi. I replaced the plugs about 1500 miles ago or so as part of some routine maintenance but the ones that came out didn't strike me as bad and it had been running normally. It did have a bit of lifter noise on startup and I ran some Seafoam in the oil (in the recommended amount) for a couple hundred miles and it mostly quieted down, the recent oil change was to get that out.

I haven't seen any smoke under acceleration apart from this recent stuff. Even now it runs great apart from the idle thing but it's sidelined until I figure this out. The only recent changes I can think of that would be relevant were the Seafoam and my nephew making it buck around like a bronco while learning to drive a stick. Maybe related, maybe coincidence... who knows.

Your nephews' lack of driving skill won't blow a head gasket (not good on clutches, drivetrain and nerves though lol) Try a head gasket/combustion test kit to narrow down the possible cause. The 4G64 is a forgiving engine to work on and if you need a VRS/head gasket kit you can do the whole thing and replace valve stem seals etc while it's apart.

if it's sucking down an over flow bottle of water after it cools off then I would start to look at a head gasket problem. But since it's winter it could just be a cold exhaust pipe. If you put a vacuum gauge on it and the needle whips back and forth then you can have a problem. But the best thing to do is watch the coolant use.

Geezer - I was definitely pricing out motor mounts afterward just in case. :) I'll dig in over the weekend and see where it goes. Thanks again for the advice, much appreciated!

Camoit - I thought it was winter condensation at first, but it smells. Not the sweet smell I'd expect of coolant, which is what sent me down the path thinking it might not be a head gasket. But that might have been wishful thinking. Also, it's way more in quantity than it was last winter when I bought the truck. Something's definitely up, unfortunately. I should give the vacuum gauge thing a shot this weekend, just need to get one!

Just want to say I'm grateful for this place and the expertise of the folks here. There's so much more value in personal experience than a shop manual will give you. Looking forward to getting "Frank" back on the road.

Had time to run a few checks today, no smoking gun found yet unfortunately. Here's what I did see:

Compression test, all were within 5 psi from highest to lowest. According to the Haynes shop manual I have, spec is between 130-150 so these appear to be healthy numbers.
- #1 - 145
- #2 - 143
- #3 - 140
- #4 - 143

Unfortunately I do not have an air compressor so I can't really perform a leakdown test here as far as I know.

While the plugs were out, I turned the engine over and wasn't able to make out which cylinder(s) were seeing coolant. Looked for any drips of liquid around the spark plug holes and didn't see anything obvious. It's got to be getting in there somehow though. Sprayed carb spray around the area of the intake manifold gasket while it was running, no reaction. Checked the torque on those bolts anyway, no smoking gun and no change.

Got a vacuum gauge and hooked that up. At idle, it sits steady at 22 inHg / 530 mmHg.

The smelly smoke/vapor persists. It made a puddle under the tailpipe after a few minutes, I soaked some up on a clean paper towel just to see if there are any telltale signs of color. We're about to get a good size (by North Carolina standards) snowstorm and yanking the valve cover to check head bolt torque will have to wait until after that. As always, open to other ideas of course.

No engine misfire under load, no chalky foulded spark plugs, not having to refill the coolant overflow tank~ try barhs leaks valve stem seal treatment ~ use half a bottle then on next oil change use the other half ~ O'Reillys might have a free rental coolant tester that changes color if there are combustion or exhaust gases getting into the coolant ~ this test will let you know if coolant is getting into the cylinders ~ keep at it until you nail it THUMBS UP

If you are getting consistent cold ambient air temps and there is a lot of moisture in the air, it'll make it's way through the intake. No distinct sweet smell of ethylene glycol coming from the exhaust and your coolant return levels aren't dropping, it has to be another source of water/condensation. Remember you'll get water dripping from the exhaust on a healthy engine when it's new so it's not necessarily a sign you have a problem lurking somewhere.

There is also the issue of the seafoam you ran to clean up the lifter tick - that may be what you are smelling in the exhaust and seeing as white smoke as it burns off. With the compression where it is at, and not using coolant or seeing it in the oil, the motor appears to be fine to me.

Well, joke's on me. Pennyman, you're exactly right.

I kept thinking there must be something I was missing and there was. Yes, I'd added Seafoam to the crankcase to clear up that sticky lifter, and the rest went into the tank which was right around the dose they say to use. It never crossed my mind that it would make the exhaust stink so bad. I know the spray can type does that, but never thought using it in the fuel would. Refilled the tank with fresh fuel and magically the stink is gone. Fine by me, I'd rather feel like a bit of a dummy than have to replace a head gasket.

The pros - Using it in the crankcase cleaned up the lifter tick pretty well. Using it in the fuel made a noticeable difference in how smoothly it runs and especially idles.

The cons - It stinks so bad I thought there was something seriously wrong. Makes a surprising amount of smoke when used as a fuel additive.

Thanks to all who contributed here, just thought I'd let you know the thrilling conclusion that the truck is just fine and I learned a lesson. :)