You don't.

 

Hey Amxal--I also live in the chicago area (well more near the Wis. border) and am having the same exact problems you are with the wet weather. However, it was doing the same thing last spring, and I changed the wires, cap and rotor, and it solved the problem. That is until now. My SES light is also on, and they told me the same things about the gas cap, and multiple misfires. I find it hard to believe that I need to change the wires, cap and rotor again though. Maybe I need a new coil?? Anyway, let me know what happens with you. Good luck.

 

Is the 98 motor DIS? If not, then BASE timing MUST be set.

 

You cannot set the base timing on the '96+ motors. The distributor hold down clamp fits onto a square drive on the base of the distributor. There is no adjustment that can be set, period. The only thing you can do is make sure you are on the right tooth down at the cam gear. The rest is handled by the PCM.

And no, it is not DIS (distributorless ignition system).

 

I agree, you cannot do anything with the timing for a 98, just drop the dist. into the right tooth. I tried the trick of spraying a fine mist of water on the engine, (wires, cap, plugs) last night and I found nothing....no light show. I have not changed the coil and to the best of my knowledge it is original. The thought of replacing the wires,cap and rotor has passed my mind, except I've done it 2 times in the last 2 years, I am using AC Platinum Plus plugs, the best Napa wires, cap and rotor (I did not go cheap) I have had to replace the cap 3 times, the last time (before the new dist) I puta bead of silicone where the cap meets the dist. to help seal...can't say I saw any improvement, but I do know you have to be careful when tightening the cap down so you don't crack the dist.

Thanks for all the help and ideas, I'm still open to all.
AMXAL

 

Ah, this is news to me. Wonder what GM was thinking on that score.... Maybe they got tired of folks tweaking the timing a bit? Upsetting their carefully scheduled emissions stuff?? Curious.

@OP: What are your plugs gapped at?

 

Well I dropped the Blazer off at the shop today for repairs tomorrow, the mechanic prepped me idea that he may need to change the spyder, said that maybe the pop off valve (s) could be sticking. I would have thought the pressure flush he performed last week would have cured that. In any case he said repairs could be $500 + for the spyder replacement.

 

Sorry for being mechanically DEclined but, what'a a spyder? And pop off valves? Never heard of them................

 

I would get rid of those platinum plugs and install what GM recommends before letting that mechanic do anything else. Platinums are never really needed unless they are specifically recommended by the manufacturer.

 

Um, AC Delco Platinum plugs are what is installed from the factory and are what is recommended... Specifically double platinums.