Hello everyone I am new to the forum and am in need of some help. My 98 blazer has an issue with p0306 and will throw only that code. But it only happens if the temp outside is below 85 degrees. If its 85 or warmer it runs flawlessly. And will drive around town all day at 25-35 mph no problem. If the temp falls below 85 or I take it on the highway and it gets cooler air number 6 wont fire and I get a flashing ses light with the p0306. If I park it for 20 minutes and restart it will have no issues again. I'm stumped I have changed the spider fuel filter distributor plugs wires and coolant temp sensor. Where should I go from here?? Thank you in advance for any help you can give.

 

I see you replaced the dist cap etc.... did you use GM parts?
I don't see new plugs listed.

There are lots of post about problems with aftermarket parts.

This is just general info I pulled up from ODB-codes....

Causes


A code P0306 may mean that one or more of the following has happened:Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective computer

Possible Solutions

If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.
If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

 

Since you've replaced all those things without the code changing, my guess would be a weak cylinder. Run a compression test.

Also try switching to 1 or 2 step hotter plug for that cylinder.

 

I agree. Something must be affecting that cylinder specifically. If the compression shows good (consistent within +/-10% of the other 5 cylinders), then airflow could be compromised in some way (ex. a collapsed lifter or a wiped cam lobe). You can measure the valve lift with a dial indicator, but to do it properly, you really should remove the intake manifold and measure it off of the lifter body itself.

 

Redroc.....My bad....I read plugs wires as "Plug wires"