My 2000 chevy blazer has been misfiring lately. Every morning when I drive it's really bad; but only at low speeds ,like between 10-30mph. At high speeds it's fine. Later on in the day I'll park it for a couple of hours then come back and drive it and it's completely fine, no misfires, shifts fine. What could it be

 

I would start with a complete tune up (plugs, wires, cap, rotor, fuel filter).

 

Yeah ive done all that except the fuel filter. as of right now im replacing both coils and see if that helps

 

I Have been having this problem where from a cold start my 2000 blazer hesitates and doesnt want to go but it only happens at low speeds. When i get about 35 it clears up, then also after being driven and it warms up it clears up at low speeds too and drives like nothing wrong with it, til the next morning and its right back at it. I have Po300 code too for multi misfires and Po327 Pending code.

Heres what ive replaced so far.

Spark Plugs
Wires
Dist. Cap and Router
Both Pick Up Coils
Fuel Filter

I think it might be a fuel pump or maybe the knock Sensor, any ideas?

 

I had this issue, I replaced the injector, plugs and cables, cleaned the MAF, fuel filter, oil filter, turned out to be my cap and rotor....

Does it make a difference if its damp out or hot? if so I would check the cap and rotor for sure.

 

Probably the cap/rotor as has been suggested. Use quality parts if/when you replace these components and make sure that the drains in the distributor base are clear while you have the cap & rotor removed.

 

It doesnt matter if its hot or damp outside it does it every time until it warms up then drives fine. But i think i found the problem. My Fuel Pressure is at 55 and the specs say it is supposed to be between 60-66. Im thinking a weak fuel pump

 

My 01 blazer doesn't start misfiring til it gets up to operating temp. When I start out in the morning the first few stops I come to it idles fine. When it get to temp it almost stalls at stops, it idles terrible, shakes the whole vehicle, and smells bad(really stinks like brimstone). When it's at speed it runs great. The SES light is on and flashes intermittently. Codes for #1 misfire and injector circuit come up when scanned.

 

I have seen many vehicles which have no problems and have their fuel pressure around 55psi. The accuracy of some gauges leaves something to be desired. So I wouldn't take this as an ultimate "the pump is bad" indication.

Follow the EGR cleaning thread in the Tech Article section.

 

Just replaced the pump, didnt work, and sadly it was a waste of time and money. so now im focusing on my SES Light code Po327 which is Knock Sensor-Low Voltage (or something like that). I read online that a bad knock sensor can cause poor acceleration, sluggish engine, specifically at take off. which matches to all my symptoms.