I just put in 6 new AC Delco spark plugs. As far as #5 being that messed up is a mystery to me too. All 6 of those plugs were from 18 months ago. I had no problems with my Blazer before my spider injector went out. I didn't use Ac Delco wires, cap and rotor but it was fine for 18 months so IDK why it just not decided to mess up. I just recently started getting P0101 and P0442 error codes too. This check engine light is going to be the death of me. Any other ideas to stop this light? I'm about to take the darn thing to a Chevy dealer.

 

Well no luck figuring out the light. I still get a misfire code driving up high doing 70mph (very high end scanner says rand misfire and cheap scanner says P0303).
Lower Intake Gasket (b/c it was leaking). A little time after this I started getting the SES light.

All Spark Plug Wires
All 6 Spark Plugs
Distributor Cap and rotor
Fuel Filter
Lower Intake Gasket
3rd Cylinder Injector
Oil Change

Is there anyway to test a distributor or is it just buy a new one and hope that fixes my problem? If that does do it then maybe the fuel pump as its PSI is just a tad low. I just want to bash my head against a wall.
I took it into a Chevy dealer and they wanted to start by checking the 3rd cylinders plug and wire (remember the cheap scanners give a 3rd cylinder misfire). However, they didn't listen to me on everything that was changed and wanted to charge me almost $250 for labor and parts. I think $250 is a little high to change 1 plug and 1 wire I did less then 2 weeks ago.

Any other ideas?

 

Have you checked the cam retard?
Pull the distributor and check the gear for worn teeth.
Injector #3 may have a problem.

You might also want to do a cylinder leakage test. Pressurize the cylinder with compressed air when its at TDC on the compression stroke and then listen for air coming out the exhaust or the throttle body. These engines can have an issue with sticking valves under load (cylinders 3, 4, 5, & 6) There is a GM TSB for that problem.
In very basic terms, a compression test tells you about your engine's ability to generate cylinder pressure, and a leak down test tells you about it's ability to hold pressure.

 

Yes I checked and my Cam retard was way off but I was able to get it back to 0 about 2 weeks ago. Checked last night and it's still at 0. I did not pull it all the way out though to check to see if the teeth were worn. I did a compression test using a gauge when I pulled all the plugs a few weeks ago to put new ones it. If I remember correctly all 6 cylinders came back very close to each other around 180 psi. Since I've replaced all those parts I'm tempted to just buy a new distributor and fuel pump. Yes it's $400 but I know my fuel pump is a little low. I tested it about a month ago and if I remember correctly it was near 58 where spec is 61-66. This morning I made it up the big hill that always gives me problems with out my SES light coming on. It did come on last night going home and before I left work I switched out all 6 spark plug wires.

 

If you want a distributor, this one is all aluminum. I have one. $41 + ship - no tax. Works fine. I switched cheapo cap/rotor to Delco.
Skip White Performance Detail Description

I'm curious what software or scanner you are using to check camshaft retard.

I have had two different AC Delco MPFI conversion kits on mine and both regulators gave 58psi at the fitting with fuel pump activated/engine off (second one installed because first one was at 58psi). I know a lot of creedence has been give to the 61psi min spec for proper operation/starting of a Vortec V6, but I think that spec truly applies to the original unconverted systems with the poppet valves. In any case, fuel pump is tested by dead end pressure being at much higher pressure than 61 psi, and the time it takes for pressure to leak down. No need to replace unless it fails. See sticky at top of this forum on fuel pump testing.

The TSB on misfires going up hills is having too tight of valve guides. Probably not very applicable to a high mile engine. But weak/shot valve springs could do it too. I think that is a pretty big long shot.

Question I have is if there is actually a felt miss or lack of power when the problem happens. If no felt miss, but misfire codes being set - I can attest that excessive bearing clearance can cause false misfire codes. Any ticking or knocks when warm? What is oil pressure at idle in drive when engine is COMPLETELY warmed up (assuming 5W30 oil). Being fully warmed up and a downshift from 4th to 3rd while going up hill at 70 mph would get you to an RPM where a bearing could rattle and the code could set. If you happen to stay in 4th gear, then maybe no code. You need to observe your tach. Colder days could make the oil thicker and thus avoid the code being set if this is your problem. Keep in mind that antifreeze in oil is definitely not good for engine bearings. Not saying this is your problem - but you should keep it in mind and not refuse to consider it.

Has anyone disturbed the crank sensor or front cover in any way? If so a crank sensor relearn is required in order for the misfire detection system to work properly.

If you have a scanner that will monitor live misfire counts, you can easily test misfire detection by inducing a miss in each cylinder and looking at the counter for that cylinder.

 

I haven't had the SES light come on since my last post. I hope it magically fixed itself. I'm using a Snap On EESC318 Solus Ultra scanner to check the Cam retard. As far as when it misfires going up the hill sometimes it's noticeable and others not so much. Usually my RPMs jump 200-250 and feels like my car is downshifting. The oil didn't look like it had any antifreeze in it when I changed the oil last week. Yes I use 5w30 in my Blazer. My oil temp on the gauge is almost always straight up and down when warm (sorry with out running out to my car right now thats the best I got). I live in MN so it's cold up here but since I've been having the problems the weather has ranged from 50-20 degrees. The last few days it's been the normal cold (actually above normal for this time of year) so I don't think that is playing a factor in the misfires not showing up. We did take apart the engine to put a new lower intake gasket in and the distributor was removed. So I assume that would effect my crank sensor and probably need to be relearned.

Edit: On my way home the stupid light came on for misfire.

 

I went 2 weeks with out the light coming on. Here in MN those were a few very cold weeks. This morning driving into work I got a P0101 and P0300. I checked the data that was stored and this is what I got. Could the mass air flow sensor be bad which fired the P0101 code and in return cased a misfire?

https://www.dropbox.com/sh/309f9crtf...5vTSp6CRa?dl=0

 

After changing plugs, wires, cap, rotor, distributor, injector poppet, fuel pump and fuel filter my problem was not fixed. I took the Blazer into a Chevy dealer and after 4 hours of working on it they think it has a bad 3rd cylinder intake valve. Looks like my Blazer is F'ed. Thanks to everyone who tried helping me out.

I guess I could pour some Seafoam into my intake and see if a miracle cures my problem.

 

I don't buy that line of crap Maybe they don't know what it is, and they told you they "think" it's a valve to "scare" you away. That tactic is used far more often than you could imagine. Burned suggested a cylinder leakage test back in post #13. Results of that would tell you 100% if a valve is leaking. Applying compressed air into the spark plug hole, (special adapter) will force the piston to BDC and both valves will be closed. If you hear air through the tailpipe, exhaust valve. If you hear air through the throttle body, intake valve. It's that simple!


Did you install an AC Delco cap & rotor yet? You might be surprised at the results If not, at least you'll know you have the best possible part installed.


Make sure camshaft retard is at zero degrees immediately after a 2K rpm throttle snap, (Solus).


Perform the crankshaft position sensor relearn, (Solus).


Post all 4 numbers from this: https://blazerforum.com/forum/2nd-ge...eakdown-88305/


Perform an injector balance test, (Solus).


Perform a cylinder contribution test, (Solus).


Then, just for grins and giggles, plug in that Solus again, only this time, don't cruise down the freeway while you're testing Engine at idle, normal operating temperature, (195F - 200F), PCM in closed loop, Transmission in park or neutral, all accessories turned off. Post images just like you did in your previous post.

 

just wondering if you ever figured out the problem. having very similar thing happening to mine. (2003)