Question about 1993 Isuzu Trooper
I can tell about a couple of odors from oils that are quite indicative of the places where they oil is leaking into the exhaust though.
You've got a few internal places where oil can get into the engine and even some can get into the combustion chambers. They have distinctive odors and can really help diagnose the cause or reason for the oil consumption.
First let's start with the "sweet-smells".
This means that the oil have gone through the combustion process along with the engine's fuel (gasoline or diesels too!). It is about the same smell you get whiffing the exhaust on a 2-cycle engine with gas-oil premix.
Places where this CAN happen:
1) Cylinder walls ie; piston rings, worn or broken.
2) PCV system where the oil is sucked into the manifold under vacuum and is entrained into the combustion chamber in the normal air-flow to the engine for combustion.
3) Intake runner-to-head surface gasket(s) where the intake can actually **** oil from the cam tray area or the inner valley between the heads and the intake manifold.
4) Occasionally from changing spark plugs in "well" type plug chambers that let the plug get very close to the head through the head casting. Taking a plug out and letting the collected oil fall into the cylinder is usually a temporary situation, but can scare you when it happens.
5) Cracked head or blown head gasket: this usually has to happen where the head has a high pressure passageway for the oil to travel through the head to get to a cam tower on top of the head.
6) Now - here's something that's gonna get debated, fer sure! ONLY the intake valves can leak past their stem seals and allow oil to travel down the stem onto the combustion process. Remember that I am speaking or "sweet" oil smell here.
Now some of the "not sweet" or bitter oil smell:
1) Exhaust guides or stem seals on the EXHAUST valves ONLY can cause a very acrid smell of nasty, eye watering and cough-inducing stink.
2) CVCC or pre-combustion chambers can also cause this problem. The Honda CVCC engines were notorious for this! The auxiliary valve can leak oil into the pre-chamber and then it opens the valve and dumps the burning mess into the main cylinder head area and the results are a bad BAD stink and lots of white/blue smoke.
3) RARELY...very rarely the exhaust port AFTER the exhaust valve seat can become perforated and allow oil to get into the exhaust stream. It does NOT burn here - rather it just cooks-off with a very bad smell.
Acrid oil smell - the oil has NOT gone through the combustion process in the cylinder head but is rather "cooked" into a stinky odor. It may or may not smoke too much too.
Sweet oil-burning smell - oil that has been burned as part of the combustion process in the combustion chamber on one or more or even all cylinders.
Posted on Mar 20, 2009
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Posted on Jan 02, 2017
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