Ok Guys, my daughters 96 blazer lost #1 cylinder, had a code PO 147 and PO 301...both codes O2 sensors...changed both..light still flashes...miss still there..changed plug and wires, cap & rotor...still misses on #1 cyl...plug is black....rest are clean...any ideas? thanx.

 

Bad valve seals? Bent valve? Bad rings? Blown piston?

Start with a compression check.

And the P0147 code is for the rear most O2 sensor (B1S3) and has nothing to do with actual engine operation as it monitors the efficiency of the catalytic converter only.

And please do not double post.

 

sorry for the double post...new to this. As far as the sensors, i wondered if they would cause a miss.it runs great above 3000 rpms. lots of power. misses bad at idle and under initial takeoff. plug is black..runs like a bad lobe or burnt valve. Daughter overheated it 3 yrs ago. i replaced 4 valves. problem started when i parked it outside on wednesday. i live in minnesota..wind chill was 32 below zero. it sat outside for 4 hours. started it up . and instantly went into a shake at idle and lost #1..I'll do a comp test and see where its at.. thanx.

 

did comp test...#1 got up to 90 lbs...dropped instantly to zero...Checked # 5 125lbs...stayed up for 30 min...checked #2, 125 lbs... stayed up for 30 minutes... looks like i'll be digging in again...

 

You can do a cylinder leak down test to see where you have to go from there. This does require an air supply though. Basically, you rotate the engine over until the valves are closed on that cylinder, hook an air hose up through the spark plug hole, and listen for air escaping. If it comes out the intake, you have a bad intake valve. Exhaust, bad exhaust valve. Valve cover breather, bad rings. Bubbles in the radiator, bad head gasket.

You can also repeat the compression check, but this time, squirt some oil in through the spark plug hole. Spin the engine over and see what it reads. If it picks up, the rings are the source of your problem. Oil allows for a better seal.

 

Thank You Sir, That sounds like good advice. My Brother-in-law has a leakdown tester we use to use on his Modified stockcar, I'll put it to work again..

You Know..since you did mention bubbles in the radiator, when i took it out for a drive, the outside temp was 10 degrees above zero. i got it up to normal temp around 195, and i did notice it jumped to 215 degrees real fast, and instantly dropped back to normal.I drove 2miles back home, and didnt see it do it again. Is that normal? would that indicate a bad head gasket? I'll still do the leakdown test.

 

removed cyl head, replaced ex valve #1 cyl....did compression check, 150 lbs on every cyl,not bad for 151000 miles...installed distributor with rotor aimed at the # 6 on the housing. #1 compression stroke, TDC...lined marks on timing cover from balancer...did i do it right with the top line on the balancer with the notch on the cover? and the bottom line on the balancer with the tab on the cover?... it fired right up...but still has a bad miss. engine light flashes. wires are on correct, new cap & rotor, plugs. could it be a bad injecter? or do i have it off a knotch? I did another TDC check, and the rotor is right on the #6 on the housing. I've built over 100 V8 chevy racing engines, and have never had a nightmare like these 4.3 motors. also, is it possible to put a HEI distributor and intake manifold from a 92 4.3 on this motor? any help is appreciated..thanks..

 

I would start looking at the ICM and coil.

And about the HEI distributor, the ECU will complain about not having control over the distributor, but it would likely run.