So I just went on a business trip and encountered some issues along the way.

Essentially it began when I was doing about 100km up a hill. My engine light came on (was blinking, was not the usual oxygen sensor code) and I was smelling burning oil. At the top of the hill I pulled over, turned off the blazer and scanned the code. It said I had random/multiple misfires.

I checked the oil dipstick soon after stopping just to make sure there was oil still in there (I had checked before I left), and oil level was still the same. However, I noticed that some white smoke was coming out of the dipstick hole. I never noticed any smoke coming out of engine itself or exhaust. I waited a bit and then drove again. I stopped a couple times along the way just to let things settle, but it felt rough going over 90km (limit is typically 100km). It also felt like I was getting less throttle than normal at these highway speeds; city driving was ok but still felt rougher than usual. Felt like it could have been misfiring often, specifically after a few minutes of driving.

A couple things to note:
- this was during a heat wave where temps went from like 20*C to 30*C on the first day of driving. My temp gauge hung around the usual 90*C like usual, and I know this was working because I noticed whenever I started up in the heat it would start at like 100*C then cool down quickly.

- the oil was dark but wasn't quite near the 5000km point where I usually do oil changes. Engine has close to 280,000km.

- I have encountered misfire codes in the past on rare occasion while driving up hills on highways, but noticed no significant changes. I've suspected it may need new sparkplugs (bought it a year ago, and plugs weren't changed for at least a couple years before then).

- I typically smell that sulphur smell (lightly) when I chug up hills.

- Also I still have studded winter tires on because a shop wouldn't put my all-seasons on the rims for now. I assume that, because they have so much traction, that my engine is pushing harder trying to maintain highway speeds than with all-season tires... Anyone have thoughts on this?

So basically here's what I want to know. I plan to do an oil change and change sparkplugs/wires (I have quality ones). But I'm not sure how to check if there's maybe a valve cover leak or to see if oil is maybe mixing with gas in combustion stage? Specifically I'm wondering what order I should do things here: if I do oil change first but find oil in the plug compartments, then I would end up having to redo oil change at some point. But oil change is much easier for me to get done than plugs.

So what do you guys think?

 

Almost guarantee the wires are the issue. Start it up in the dark and look around at the wires. If there is arcing , you`ll see it. You may need to increase the rpms.. The sulpher smell is from the bad wires

 

Interesting, so I take it this has happened to you before?

So you're saying that the spark just isn't making it to the plugs in the first place?

I will check it out tonight to see if there is arcing.

 

Yes it has, not all the spark is making it, Even if you dont see arcing I would still pur my money on the wires

 

Probably be a good idea for him to also replace the spark plugs and cap/rotor with AC Delco (no other brand) and check to insure cam sensor retard is between -2.0° to +2.0°. These are all common problems with performance on a Vortec V6 or V8. Any of these problems will stress the rest of the ignition system (for example a bad spark plug wire can cause carbon tracking in the cap or rotor, as can cam sensor retard being off) and end up as a misfire code and SES light. With 2nd gen Blazers, i think it's best to shotgun the ignition system parts when you are dealing with a misfire. These parts should be considered consumables.

ACDelco D465 Professional Ignition Distributor Rotor by ACDelco
$10.53




ACDelco D328A GM Original Equipment Ignition Distributor Cap by ACDelco
$25.29


ACDelco 9746KK Professional Spark Plug Wire Set by ACDelco
$46.78




ACDelco 41-993 Professional Iridium Spark Plug (Pack of 1) by ACDelco
$6.27 each