Hello,

It's been a month and a half and I still have the P0304.

I did go ahead and replace the whole distributor. Did not fix it.

Every once in a while, I'll get maybe a day with no P0304 and will get P1415 sometimes, but before all my monitors are "ready" for inspection, the P0304 will return. I've also changed the AT mount as I discovered it was broken. I didn't think it would fix the P0304, but still had my fingers crossed.

I've checked my MPG the last month or so and consistently get near 21, about 80/20 hwy/City. That's pretty good, is it not? for a motor that skips and over 210,000 miles?

Well, I've been driving the vehicle with expired tags for 2.5 months, constantly looking for cops and avoiding areas where they are usually seen.

I am really tired of this.

Anyone got any suggestions?

Thanks!

 

If you havent tried trading spark plug or wires with one on the other bank try that, i dont remember if youve mentioned plug wires or not. If the misfire doesnt follow the wire and plug then you know ditributor is good and the #4 plug and wire are functional, did the distributor come with a new cap and rotor? If the cap and rotor are new, distributor is new and the misfire stays on #4 when you trade plug and wire to opposite bank then its fuel or compression, the 130 psi you originally got should be enough to burn the fuel and make enough power that the computer shouldnt be able to detect it, the odd thing is, if it was a straight dead cylinder missfire it will usually give you a blinking check engine light so it must be firing sometimes, also, with timing chain wear and other mechanical wear it makes the computers ability to detect the exact cylinder very inconsistant but you had said before that pulling the plug wire from #4 causes no change in roughness so i assume we are chasing the correct cylinder, also in case we didnt cover this, the plug wire locations on the cap are not in order front to back, please rule that out too, if all these ignition rechecks i just stated are good then we need to move on to fuel.
Possible things causing lack of fuel to one cylinder: Low fuel pressure(new injector and new "spring loaded" poppet may require a few more psi to open than the old ones, sticking poppet, sticking injector, Bad electrical connection at the injector connector pin, injector wire broken inside insulation, high resistance in the injector wiring, loose pin on injector connection at pcm(unlikely but possible), failing injector driver (transistor) inside the computer, these are a hot internal component and can cause solder joint cracking on the circuit board too. That covers almost every single cylinder fuel delivery problems ive ever seen. If i was at home i would get the computer pinout and have you test resistance between each injector wire at the engine and computer to make sure we have a good path to and from.....but i wont be back there for a couple days, you may be able to find one on the internet if you search around. Theres a test you can do to see if you are getting power to the innector but its a delicate procedure, i will try to brush up on this circuit design so i can tell you how to test without damaging anything, its different for different year make models and if you do the wrong thing you can fry the computer, but the safest test you can do is backprobe the connector with a volt meter (no test light!) at the injectors, you will need to remove the cover from the top of the plug so you can see where the wires go in, get a metal paper clip and sharpen the tip to a point, stick it straight down alongside the wire and check for voltage between each wire and ground on the engine or battery negative with KEY ON, try to find power to all 6 injectors and mark or remember which ones they are, if you find power with key on that means that the injectors are ground side switched (by the transistor) inside the computer , now if you stick your paper clip in the negative wire and use a test light, yes test light now, connected to battery positive and touch the paper clip you should get no light, the other side of the injector will also be positive as long as there is no ground, now if you start the engine and touch that paper clip the test light should blink if the computer is giving the injector a ground path. Im going to try some quick internet study to figure out if this system works like this, in the meantime please rule out and verify the ignition stuff i mentioned earlier, i want to figure this out as bad as you do but its really hard when i cant be there and i know parts have been changed, especially because i know that the failure rate of aftermarket parts is very very high so it worrys me that im just chasing my tail around some "Assumed Good" part that was bad out of the box....it happens alot, i once got 5 bad mass airflow sensors in a row, went to a different store bought the same brand and never had another problem, first store just had a bad batch i guess but it had me about to give up on working on cars altogether!

Anyway sorry for another mile long post, hoping i can help you get to the bottom of this. Just be careful testing injector circuitry and remember that a test light is essentially a jumper wire so it can short circuit things, a volt meter just takes a sample of whats there, when i tell you to use the test light its because we have verified circuit design and need to see the light to verify a pulse.

 

I've learned that on a 2005 blazer, (maybe applies to your year blazer) you must check camshaft retard settings with a good scan tool. Make sure it is within spec.


When you replace a distributor you must tell computer to run "relearn on camshaft retard" I think the crank sensor provides that info to the computer.


Why is it that these vortec engines never run worth a **** as they age. seems like misfire city engines.

 

Well here's my update: I still get the P0304 and sometimes a P0300, however, never at the same time.

I have noticed this, which may help in the diagnosis: The codes are only thrown when started cold (overnight start or at least sitting 3-4 hours).

I can clear the codes at night, cold start in the morning and instantly get pending P0304 or P0300. Sometimes, rarely (5% of the time) the SES will flash for about 20 seconds and then go out. I have discovered that if I drive the car about 5 miles, restart engine and let it idle about a minute (or drive it) and repeat 2 to 3 times the pending code will go away. It will of course come back the next morning, or sometimes in the afternoon if the Blazer has sat all day. I can again do the restart trick 2 --3 times to get rid of the pending code. If I get the confirmed code, I can do this restart procedure about 5 -6 times and the SES will go out; however the code remains. I understand 40+ cycles are needed to clear that.

With all that being said, it looks like i only get the misfire codes upon a cold/ semi-cold start.

Does this information help in what I can rule out and where I should concentrate?

As always,

Thanks!

 

If the SES light flashes it pretty much always means the computer is detecting a dead cylinder, it may or may not actually be #4 when it gives the P0304 code, most times they are pretty good at detecting a flat out dead cylinder, the times you get the P0300 the cylinder may just be missing here and there or not producing the correct amount of power. Since you dont have expensive diagnostic equipment I dont know how you are going to find it without just throwing parts at it. My current Blazer gives me a miss sometimes now too and sometimes its set P0300, sometimes it gives me P0304, I know for a fact that mine needs a new distributor cap, I washed my engine after rebuilding my ac compressor and it started missing, i left it running while i washed so i would know what i sprayed that killed it if it stalled, well i reached back and put my hand on the distributor cap and got some light zaps and tingling. These caps are a terrible design and they will crossfire within the plastic that cap is made of. Try soaking the distributor with the engine running and then put your hand on the cap with the engine running, grab each plug wire and follow it from cap to plug, also grab the ignition coil and its wire. This wont kill you, ive been zapped many times, s s s s s ss s ss ss s ssss ss 66 TIMES.....I hope someone can guess what movie thats from...
Anyway, if you get a tingle from somewhere thats where you need to concentrate.
If you dont find anything in the ignition system, which you may not because just now i re-read post #12 and you stated that when its missing there is no change whether the cylinder is connected or not. If this is true and you can get a good spark to jump from a screwdriver stuck in the #4 plug wire to the block and you have tried switching the spark plug then you probably have a fuel issue on that cylinder. Possible reason/scenario, the #4 injector that you replaced may have a bad poppet? The injector itself may not functioning right mechanically and not allowing enough or any fuel.
Also, on the ignition one more time, you replaced the distributor recently, did you replace the cap and rotor with it and how about the plug wires, you said you replaced the cap in december when you did the LIM, DO NOT ASSUME THAT THEY ARE GOOD. I have had these cheap distributor caps and rotors go bad in 6,000 miles, if you bought a store brand or something in a shiny package that said NASCAR on it you better just go get a new set, an AC Delco!

In my opinion you have enough compression for the cylinder to fire and make decent power....however, you have not performed proper compression tests so that cant be confirmed, a proper test needs to be with all plugs out, throttle wide open and you keep cranking until the needle stops rising, not for a specific amount of time, also a battery charger should be connected and turned to boost so that you arent getting your last few cylinders on half cranking power, a pair of decent jumper cables hooked to another running car would work too. On the same note if proper procedure was followed you probably would have gotten better numbers so dont worry about it.
You are lacking spark or fuel, if i were in your shoes and I was sure i had GOOD spark at the plug I would try swapping that injector around to a different cylinder if possible or buy an injector assembly from a junkyard and try that, they go for $75 in my area .

I hope you get to the bottom of this soon.

Remember, DO NOT assume your distributor cap is good...

 

Thanks DimeBlazr!

I did not read your post until this morning. I'll try the water deal over the weekend. I've been zapped a few times over the years, even a few times with 110 V AC (that CAN kill you! haha).

What I did do last night, dark, no moon, was run the engine and I did see a faint flashing spark/glow where my No. 2, 4 and 6 wires meet the distributor. I tried to touch the glow area and did not feel any shock.

Does the fact I can see the glow (albeit faint) indicate a spark leak? Should it have been all dark?

 

Well the glow is never good, although i havent tried looking with new or properly functioning parts, but i bet thats going to be your problem. Check each plug wire terminal in the cap too, should be nothing but shiny, if you see any carbon or discoloration you need to replace the cap and wires

 

Hello, When I went out on this P030X quest a year or so ago, I found many lengthy threads here and there on the subject that never fully came to a solution.

This thread is no exception; nevertheless, I thought I'd give an update and partial closure to this:

My solution to the registration was that last September I registered the vehicle in a county where we own property that is outside metro Atlanta and does not require emission testing. Had to change my license to there as well. It is/was nice being able to drive and not be on the lookout for law cars! Felt like a criminal! Tag was expired for over 4 months, driven nearly everyday.

Coincidentally, the P030X went away (for a while) around that time and I do believe it is/was the faint glow I saw at the distributor on the 2-4-6 side. I doubled up the dielectric grease in that area and it is gone most of the time, but does reappear on occasion. A new AC cap/rotor/wires would probably fix it all up; however, whenever the P030X does not appear, I get P0410 and/or P1415, which will not appear if a miss code is present. The secondary AIR fan works like it should. I suspect the driver's side check valve has failed; however, I can't get it to come off.

Honestly, I really no longer care as the vehicle is registered and runs relatively well, coupled with the fact that we've also added two newer vehicles to the fleet, so the Blazer is now a 'secondary' vehicle. With over 220,000 miles, pasture is in order.

Thanks to all who have helped with this and other issues I have had and I hope I have/can help as well!