96 jeep grand cherokee intermittant exhaust smoke when air conditioner on

Air Conditioning is a completely different system than propulsion systems. There ought to be no relationship between smoke and the AC system. Except that the AC system can contribute to overheating while stopped and/or under heavy loads. The reason for this is that the AC system will warm the air going through the cooling system radiatror, causing it to be reduced in its effectiveness. It isn't so much that the AC will warm the air is that it blocks the air.

Rick did pass the time by typing:

Yes and your probably not going to like it.

Heading off water contamination in the fuel tank... Filled up at a cheap station or a low (elevation) station after a heavy rain? You may have a tank of crapoline. A gas drier that's safe for O2 sensors can help that.

However......

You may also be describing a leaking head gasket. Check the oil for coolant and the coolant for oil. White smoke is usually water being sucked into the engine and blue, oil. It is a very bad thing to continue running with a leaking head gasket as it will destroy your engine in short course.

Thanks for the suggestions! I will check the valve cover gasket. My father suggested the bad tank of gas theory. That's definately possible. I have tanked up after a rain recently at a shady place! Maybe there's some water in there, since there is no lost coolant or any coolant in the oil.

If it's burning oil, would it be intermittant ?

Thanks again, and if anyone else has other ideas, please post. This message group is great. I have gotten much help through the years. Last year it was the front axl u-joints.

Oh, another thing. I recently passed the emission test last week. No problems with the exhaust. Just a little bit more info.

More info! I didn't know this before. My father added some stop leak stuff to the oil last week! He didn't tell me. Could that cause intermittant smoke from the exhaust??

Rick proclaimed:

Stop leak in the oil *might* cause it but only if you have an internal oil leak in the engine itself..which would be not good news.

If you can see the smoke by running the thing up to goodly speed, then let off the gas.... then as the thing slows 15-20 miles per hour, gently press the gas again. Smoke then is usually stuff like valve seals, altho it could be piston rings or such. Dunno how easy it is to get oil thru a blown head gasket on the 4.0.

Would think that even with a catalyst you might be able to feel an oilish material on the inside of the exhaust...AFTER it has been gotten good and hot, then allowed to cool down. If so, the oil isn't doing your catalysts much good either.

Lon did pass the time by typing:

Easy enough just to pull the plugs and check. Take note of each plug (or take a photo and give us a link).

The only blown headgaskets in the 4.0 that I've seen sucked coolant or let the coolant get into the oil. Burning oil has almost always been worn valve guides. Never looked at the passages that closely. Feed comes up through the lifter rods and returns through the drain holes, there isn't enough pressure there to force oil into the engine.

Now on more than one occasion I've had a HUGE white cloud follow me. Almost thought I blew the engine. Turns out it was a tank of crapoline. Pumped out a cup by cycling the fuel pump and it was almost 10% water. Only tank I ever dumped.

p.s. If your going to do this, dump the gas into a large plastic or glass container and let the water sink to the bottom. Pour the "good" fuel off into a gas can and repeat. Take a while but slowly it removes the water. Then go with a fuel system drier.

MORE INFO!

Ok, I wasn't getting any smoke for a while, and I haven't used the air conditioner at all. Well, this weekend I took a trip, and used the air. You guessed it! Smoke emitting. I pulled over and looked under the car. There was smoke coming from the cat converter. It was also dripping. However, I couldn't tell if the dripping it oil or dirty water.

I let it cool down for about a half hour, and continued on. I didn't turn on the air again. No smoke

I also didn't turn the air on at all in the 2 hour ride the next day. No smoke.

I do have a small oil leak, and it's been there for quite a while. I get a small puddle wherever I park.

Can this possibly the the water from the air conditioner building up and getting into the catalytic converter ??

Rick

How about the oil, from your existing leak, being washed down onto the cat by the AC condensation??????

In this theory, with no water dripping out of the AC, the oil either clings or drips straight down. Stranger things have happened.

Just a thought.

Regards,

DAve

Well, I'm not nearly as mechanically inclined as some here, and I'll probably get crucified for this, but here it goes:

You mentioned an oil leak and burn... does the smoke occur after you "top off" the oil? (we've all probably had one of those "check the gas and fill the oil" cars at one point in our lives). Do you top it up or wait until the dipstick registers a full quart low, then add a full quart? In my experience, even new vehicles have a "happy point" with oil level that may or may not read completely full on the dipstick even though there is no leaking or burning... As Bill said, the valve cover gasket could be the source of the smell but the smoke could be a result of overfilling and due to the fact that you've got so many miles, could be some tired rings and high pressure.

I was always taught to never add oil until you're a full quart low. Too much will spell disaster for engines with high mileage.

Just a thought. Good luck!

John