Is the 55 psi of fuel pressure sufficient?

 

All about fuel pressure testing:
https://blazerforum.com/forum/2nd-ge...eakdown-88305/
Please post LT/ST trims all together.

 

Okay sorry its a friends blazer and i wont have it infront of me till next weekend most likely but id like to try to get some idea of where to check next. I feel like weve gone through just about everything. Fuel pressure held 55 lbs for 10 minutes after pump was off so i think were good there. 02 sensors seemed to check out aswell. One thing that caught my attention was that when we unplugged maf it hiccuped for a second then ran how it does with sensor plugged in even when revved up. It did eventually throw maf code so im wondering if thats normal for it to not change much if you unplug it.

 

Disconnecting MAF opens the control loop, so the injector timing is based on ECU internal timing map, not the O2 feedback. If It revs up, looks like the injectors are giving too much of a fuel (leaking?).

 

I mean when we removed the plenum it looked like fuel was spraying everywhere but once we hooked fuel lines back up it was leaking down slowing but we couldnt see any fuel. He wanted to replace injector for an ac delco instead of the cheap one from previous owner so we did that and pressure holds longer but we havnt pulled plenum again to watch it yet

 

Hm... I am running slowly out of clues. At a first glance I'd say its a fuel pressure regulator into the spider, but You have already changed them. Hardly possible two of them have a same malfunction. So, apart of the negative 12% trims, which seem to be a true reading, You are still getting P0300?
Another possibility is that something goes out of timing, so the ICM improperly controls the fuel quantity that is injected. What about camshaft/crankshaft position sensors?

And, the last resort idea is the fuel quality...

 

Has new distributor shaft and cap and rotor in it and he took it to a ahop to have it timed and a camshaft position relearn on it cause previous owner claimed to have changed it. I really appreciate you responding with solid advice.

 

...what are the O2 traces? Varying normal up-down-up...? Or they tend to stick to bottom or top?

 

 

So I had this truck in the shop (same truck as dkarll88) they went through all the new parts that went on.everything looked good. He claims it is not really missing, he is telling me that If it was missing the way it is showing on 2 cylinders It shouldn't even be able to pull out of the driveway. He checked 'my work' as in (distributor, spark plugs & wires, coil, and spider injector) then went on to do a crankshaft position sensor relearn after that didnt fix it he checked, flywheel, harmonic balancer, and even flashed the pcm because a gm tech told him that may clear it. NO LUCK. Hes said he is at a loss so I went to pick it up lost on where to turn now. Any help or things to check that may cause a false p0300 code