I have a 1998 Chevy s10 blazer that is running ruff and shaking and bad smell from exhaust like sulfur.When I step on gas black smoke comes out of exhaust.There are no codes when hooked to code reader.Mechanic has changed spiders pcv mass air flow and has made no difference.Could this be a computer problem.Car has 110000 miles and is in nice shape 1 owner and well maintained.Thanks for any help you can give

Ordinarily, rough running with a raw gas smell indicates a fuel pressure regulator or fuel injector problem, but that usually produces grey or black smoke. The white smoke may be steam, which is more serious.

If the exhaust also smells somewhat like maple syrup (that's what burned engine coolant smells like unless you are running water without antifreeze), or your coolant level is going down rapidly, you probably have a bad head gasket, cracked block or head that is leaking coolant into one or more cylinders. That's what would produce a large amount of steam, and the uneven power production is what makes the engine vibrate strongly. The mixture control system is being all messed up because the coolant in the cylinder is preventing proper combustion - on the one hand the knock vibration sensor is telling the computer that the engine is running too lean, but on the other hand the oxygen sensor is detecting the rich condition. A readout of the engine computer would be interesting to see.

Run the engine as little as possible until you get this checked out. A coolant leak into a cylinder can cause quite a bit of secondary damage.

You may be able to identify which cylinder has the problem by removing the spark plugs and inspecting them. A wet spark plug is confirmation of my hypothesis. If you have a borescope (video camera on a flexible tube or with a fiber optic bundle with a lens on the end), you can peek inside the cylinder through the spark plug hole. Otherwise, pull the head to see where the coolant leak is.

Check for dirty stuck EGR.

The Smell is-- Sulfur Dioxide-- from an over heated
Exhaust Converter

Yes-- it will be ruined soon

White Smoke all the time, could be a head gasket

It could also be-- lots of fuel-- that is overheating the converter

Have to look at fuel trim on scan tool data

possibly a faulty injector for the miss but if you have a head/headgasket problem it would account for the exhaust. Do a compression test and radiator pressure test to eliminate that area of concern

Catalyst convertor is bad.

The seeet smell is antifreeze. You have a blown head gasket or intake gasket.

black smoke is carbon have you changed the o2 sensor's??

Had a 94 Olds Bravada that did a similar thing and it was EGR valve on the front of the intake. It' s easy to take off and clean with WD 40 and if you have an air compressor blow it out good.

make sure you have good fuel preasure, start with that first.

black smoke is an indicator of too much fuel not burning in the combustion chamber, or too much carbon build up in the exhaust. you might have an injector problem, i.e. 2 much gas overloading somewhere.