Hi- I have a 95 Blazer 4x4. I just put in a reman motor from Marshall Engines through Advance Auto Parts.

It runs rough at idle, and is low on power. When using my scantool, I keep getting a p0306b=Misfire detected on #6 cyl. I have verified spark, and have new plugs, cap and rotor.

I figured maybe it's a stuck poppet nozzle, so I switched the nozzles around.

Still misfiring on #6.

Any ideas?

 

have a read thru this thread https://blazerforum.com/forum/showthread.php?t=31901&highlight=Marshall+engine

it was a Marshall engine also and it was something mechanical, cam lobe or lifter, I believe it was cylinder 4 misfire and he could not figure it out, you can try swapping #6 poppet with another cylinder, clear the codes and see if the problem follows. There is a bunch of information in there that was tried before they came to the conclusion that it was mechanical, so try everything first

 

Switched the nozzles. Still misfiring.

 

Same cylinder? If so, check the compression on that cylinder.

 

ok. as soon as i get my compression tester back from a friend i will do that

 

Tested compression, 130 on cyl #6.

I also get PO325D=Knock Sensor Mod detected
along with PO306B= #6 cyl misfire detected

 

I changed the cap (AGAIN) and the wires. now my code is the infamous po300b random misfire detected.

H E L P!

 

New distributor installed.

still misfiring.

 

The compression seems to be good, I would test all the cylinders tho and write down the compression results, to have a decent running engine you can be within 20 lbs from the highest tested cylinder. Did you use AC Delco parts when you replaced the cap etc??.... You said you swapped poppets and the misfire still on #6 so its leading me to think that it may be something mechanical, Have you removed the valve cover and checked to see if everything is moving as it should??

 

Yeah. AC delco parts. Since swapping wires, and distributor, The misfire code has become p0300, Random misfire.