Okay, so I've been through this time in and out but this is new.

i have a 04 blazer, misfire at cylinder 1. Changed the distributor cap and rotor, wires, coil and spark plugs. Still no change.

i did a compression test and it read about 120 and that sounds good compared to cylinders 2 and 3 at 140 and 160.... so to test it out, i put compression fix fluid in and the engine got a bit more quiet but over all i still have the misfire and symptoms.

I'm thinking it could be the fuel injector to cylinder 1 or atleast the fuel injector's O ring because i hear an intermittent spark and my oil smells like fuel

i know my blazer pretty well, but another opinion is always good, any thoughts???

 

Follow the Captain Hook's fuel pressure/leak down test (link below my signature) to rule out any fuel delivery issues. Probably the most common engine problem with Blazers.

 

alright so i did the fuel pressure leak down test. Key on/engine off 57 PSI....when engine turned on, the pressure gauge was intermittent but it stayed between 50 and 60psi....

when i shut the engine off and waited 20mins it stopped at 60 psi and never dropped

I cut the engine on again but this time i watched the gauge as i pulled the throttle plate open to increase RPMs.

when i did that the gauge went steady at about 60 psi

 

If you've never upgraded the CSFI spider injectors to MFI, that spider assembly is known to cause problems. The poppets are crap. The MFI set has an electronic control for each injector. A lot of us have done the upgrade. Runs about $300. A check you could do on the ignition system is to pull the spark plug and ground it to see if it sparks with a steady rhythm while the engine is running. You could also do things like switch the wire/plug with another cylinder to see if the miss moves.

 

I've done that, its not the plug or wire...the fuel pressure leak down test i did is really pointing to the single fuel injector or the seal/O ring that seals that fuel injector which is cylinder 1

cheapest thing i can do right now i guess is to take off the upper manifold cover and check out the O ring before buying a whole new injectoe

 

You have not reported any testing that will single out the fuel pressure regulator or a single injector. You already have a MPFI spider on a 2004 - they came that way Seems like you are really going down the primrose path. Not sure where you can buy a single MPFI injector.

On exactly what are you basing that there is a misfire on #1 cylinder? If you are ready to listen, I'm sure we can help.

 

I was unaware some models came with the MPFI. What year did they start?

 

My check engine light, code p0301, cylinder 1 misfire...

I'm listening

Also the dealer sells single MPFI injectors for blazers, and GM has made the specs available to a few, if not a lot, of after market parts manufacturers...so as of today, if it were without a doubt the full injector, the part would be immediately available

the injector could be dead, i hear what sounds like the injector firing wildy without a scope or screw driver to the manifold....

Or, that sound could be fuel sputtering thru the O ring, and that kinda makes sense because my oil smells of fuel, a stronger smell than before the misfire

your thoughts?

 

LU3 and LG3 MPFI 2002 saw major changes to the 4.3L fuel-injection system. For 2002 California emission Chevrolet Astros, GMC Safaris, Chevrolet Silverados and GMC Sierras all came equipped with the updated LU3 4.3L. 2003 saw the L35 discontinued and the LU3 replacing it in all other applications. A new variation was also introduced in 2003, the LG3. For 2004 to 2009 the LU3 has been the only 4.3L produced.
The biggest change to the LU3 and LG3 was the fuel-injection system. These engines used a multipoint fuel-injection system, with six Multec II fuel injectors mounted at each intake port on the manifold. GM recommends the Multec II spider assembly (which is also available for the L30 and L31 small block V8 motors) as a replacement for the 1996-01 CPI injector/spider assembly since the poppet valves have been known to stick open. The sticking poppet valves have been attributed to ethanol fuel blends sold in the State of California. The composite upper intake manifold and cast aluminum lower intake from the L35 engine is also used on the LU3. The LG3 uses a cast aluminum upper intake and a cast iron lower intake.[7]
The LU3 also received a quiet cam to help reduce vibration at both idle and high engine speeds. This camshaft used the same lift and duration as the older design, but the cam was reprofiled to keep the valve lifters in full contact with the cam lobes as the cam ramps down.[7]
The LG3 was used in Chevrolet and GMC S-series pickups and was only produced for 2003. The LU3 was used in the Chevrolet and GMC full-size trucks and vans, the Chevrolet Astro and GMC Safari vans and the Chevrolet S-10 Blazer and GMC S-15 Jimmy. The LG3 was rated at 180 hp (130 kW) and 245 lb·ft (332 N·m) of torque. The LU3 was rated at 190-200 hp and 250–260 lb·ft of torque.

Do you actually have a real steady felt misfire definitively identified on #1 by something other than the PCM, or has the service engine soon light and a specific code convinced you of it? Can you induce a real misfire and the misfire detection system will identify it correctly? Can you watch an induced misfire count up misfires in a live misfire display for the correct cylinder using a capable scanner? This is my criteria for believing P030x codes are real. If the system can't identify an induced miss, the misfire detection is malfunctioning and cannot be trusted. How do I know? I had one that gave false misfires. So please consider all of this this carefully.

 

I understand what youre saying

since i dont have a reader to count the misfires, i use and OBD reader to clear the code....now 4 months ago, it was smooth running and when i would clear the code the code it was still smooth....

but shortly after about 2 weeks after the code would come back upon start up or driving thru the city and idle...the misfire is noticeable, i fixed 2 other misfires...1 after i brought it, the spark plugs were bad...and the 2nd misfire was a vacuum leak i fixed..

i definitely recognize the shaking feeling, sound, and the rhythm the engine has with a misfire...so i doubt the pcm is setting off a false misfire

oh and the misfire stops on acceleration