[Flyer58]

To help diagnose a head gasket leak or oil leak around the valve stems try this

Drive on an open road with little to no traffic and accelerate to 45 MPH or faster then take you foot completely off the gas pedal and let the car slow down to 10 MPH, then hit the gas pedal hard to accelerate quickly and look in the rear view mirrors for a puff of smoke caused by a high vacuum in the engine which pulled in water or oil.

The procedure may vary depending an you transmission but the idea is to create that high vacuum for several 20 or 30 seconds and then quickly clear out and burn it off.

 

[Flyer58]

Andruil, I like digging for information on the Patriot yet I'm finding very little help out there. Sounds like you have several problems which may or may not be related.

You should not see any smoke up front when starting the engine so that indicates an probably exhaust leak for either a gasket, crack, or loose connection.

The rough idle after start... Does that happen each time you start the engine whether it's hot or cold or after 20-30 minutes of resting or only when sitting overnight?

Also what year is you Patriot and what engine do you have in it?

Lastly I can't find any FSM information out there for checking the fuel pressure. Obviously it will pump up to something around 35-45psi (I'm guessing) but then does the pressure stay there or immediately release to a low residual pressure. If there's no pressure in the fuel rail then I doubt very much could leak out of an injector. My YJ holds pressure for 30+ minutes but not sure about the Patriot.

 

[Flyer58]

Per a FSM, supposedly the pressure is maintained short term but eventually goes to zero.

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Thanks! My guess is "For a short while" means there's probably not enough pressure to make for a rough start issue without it also throwing codes for rich mixture or a continuous rough idle. I mean things could happen but I don't see it this time. Appreciate the info.

 

[Flyer58]

I checked my coolant this morning. It gurgled a lot when I took the cap off but I could see coolant in the tube. I added some more just in case.


It can go days without starting rough and smoking. The smoke is definitely coming from around the exhaust manifold. I had a rough idle after starting last night when I left work. It had been sitting for about six hours. This time the smoke reminded me of a fuel smell. The electrical smell the first time was after I changed the coil packs. It could have been my mind playing tricks on me or something on the coil packs.

So what we have is a rough idle on starting (only sometimes) which always seems to coincide with smoke from the exhaust manifold. The roughness will work itself out. A compression test revealed 125 across all cylinders. The oil on the dipstick is fine and there is just condensation under the oil fill cap which doesn't really get burnt off because I live five minutes from home and don't travel with it much.

The only codes I have had are the one for the coolant temp sensor (which was replaced) and misfire on cylinder 3. The spark plugs looked fine when I had the compression test done. 2013 2.4.

If the rough idle lasts long enough you can try checking the new coil packs. start with #1 and unplug the coil electrical connector then plug it back in. You should get a very noticeable change in sound/rpm. Work your way across through #2,#3 and #4. If one shows no or little change then you may have a bad new coil or spark plug. You can check coils by switching places between the bad and a good one to see if the problem follows the coil.

I installed new coils in a Nissan Rogue and have one go bad after three months. The problem was very similar to yours. If you have an AutoZone or any other friendly parts store nearby they will gladly do a free code scan to help.

 

[Flyer58]

Any code on the scanner?

Depending on how an injector is stuck, open or closed, it can cause smoke in the exhaust.

 

[Flyer58]

That does look like a black powdery soot from an exhaust leak, probably the gasket on the manifold and prior to the catalytic converter. After the cat is usually clean like the end of a tailpipe. I wouldn't be surprised if some oil leaked out from the valve cover gasket. That's an easy fix if you find oil on the backside of the engine.

 

[Flyer58]

One or two drops of oil can go a long way down the engine out even along the undercarriage. Just switch the #3 coil with any other one and see if they code shows the new location.

 

[Flyer58]

Looks ok to me. How long have you been using that plug in the engine?

 

[Flyer58]

Something else to think about is the leak may be from a cracked cylinder head which would cost a lot more than just a gasket. They are less prone to cracking but it still can happen. If you decide to fix the leak have a shop check the head for a crack. The test doesn't cost hardly anything but the repair will.