The Random Misfire PO300 code on my 1998 suburban 229,800 miles was the distributor cap I just finished changing the cap and rotor Now it runs fine-no off idle stumble-no miss-no codes-no yellow light"service engine soon" The cap contacts-8 aluminum looking studs- had "lots" of greenish corrosion crap on them rotor looked fine Didn't do the wires or plugs back hurt sooo much after the 1.5 hours bending into the bay to do the cap-rotor Anyway-thanks for the help I think one of you-maybe redy or Edward or 08 suggested that the onset of this problem in the heavy rain-suggested cap- The cap was at least 10 years old-maybe much more- The wires aren't OEM- BELDEN maximum protection- I left them and the plugs for "some other day" Buddy of mine suggested the little "ball" in the middle of the cap is spring loaded this one sure isn't-it is solidly stuck?? Anyway lucked out-not the pitb injectors-which would have been $400 and 20 miserable back breaking hours Thanks all Charlie PS I don't think I have changed a dist. cap in 30 years no need-didn't keep cars long enough to wear one out-not since maybe the 1980 D-100 OR 1986 Toyota pickup
Good work, Charlie. It's been a long time since I have seen the inside of a distributor cap , but I seem to recall a little spring-loaded plunger in the center of it. And my famously reliable 89 Honda did need one injector replaced at about 215K miles. If yours are original , you're doing good.
ksstathead edwin Better to be lucky than good!! Thanks Oh -drove it to a school-10.2 miles away-a route I have done maybe 100 times in the last 3 years. In HINDSIGHT it must have been a missing a bit for a long time Not enough to CODE-but it must have been off Because it is very smooth running Unfortunately my scan gauge has croaked-just croaked( had it since Katrina,so no complaints) I couldn't measure the MPG But about 3 weeks before the CODE PO300 and the obvious miss-it got a RECORD MPG-17.3mpg cold engine on the 10.2mile trip(average on that trip is about 16.2mpg or so depending on time of year Anyway I got lucky-just the cap-only spent $100 43.30 cap rotor $50 wires $3 PCV no I haven't done the wires or plugs yet-they can wait PS I ran it around town-for a couple of weeks-while it was missing/coding-mpg was down about 10-15% Heck I ran a 1969 Corolla SW from Baton Rouge to Denver and back-2200 miles then drove it to Key Largo from BR(about 2000 miles) all with a HORRENDOUSLY warped head head gasket leak Yeah spewing steam and oil out the exhaust-and from under the hood for 5000 miles Heck finally had it fixed-sucker ran on for 5 more years until sold The little Corolla was my kind of car--OWNERPROOF like the suburban-ownerproof
