Yes they are close to the collectors which are open at this point. Dumb it down for me a bit. Case grounded style. They are for a02 Silverado which is what the engine came from. They plugged right up. Is there a better type to get. They are 4 wire as I recall.
You'll have to ignore anything thing related to fuel trims until the misfires are sorted out and the exhaust is complete. GM uses about a 445 milli volt bias on the O2 sensor signal circuits so if the O2s are the wrong type, disconnected or the harness is wired incorrectly for the type O2s used, the O2 pods will read around 445 mv. You have an O2 issue for sure BUT since you have two confirmed cylinders down you must attack that first.
Another cause of extended cranks is lack of cam signal. It will run without a CMP signal but will take longer and often several attempts to start. I've seen 3 bad LS CMP aftermarket sensors right out of the box. Have your nephew check for a CMP signal either thru a scan data pid OR if he is a scope user it will be a 0-12v digital square wave. This won't cause your misfires though.
Start with the two misfiring sensors. Check spark, then put a noid light or scope on those two injector circuits. If those are both good, check compression on those two holes both cranking and running then check a known good hole to compare against. If fuel, spark and compression check out you'll need to check that the coil control circuits aren't crossed by the harness builder.
I know you're hoping for a silver bullet that will explain all of your symptoms and often times that is the case but I can promise you that in this case, I'm certain you have multiple root causes.
So go in this order or you will be chasing your tail.
1. Solve both constant misfires
2. solve extended crank
3. Finish exhaust
4. Solve O2 non response
The misfire could be as simple as 2 bad spark plugs. I've had 2 engines that had the spark plugs fail. 1 engine had less than 7000 miles and 2 plugs failed. The other engine had less than 40 miles and a plug failed in it.
get that exhaust finished, open exhaust will mess up the o2 readings.
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When my nephew scanned the CPU he ran a cycle of the injectors. All of them responded. Should I still use a noid light? I plan to fix the exhaust this weekend and rescan it. Thanks again for everyone's input.Originally Posted by farmtruc
Bit of an update. Exhaust is complete. Noticed the scan tool indicated the O2 sensors were not sending a signal. I removed the O2 sensors to clean them up a little. Heavy carbon. After I reinstalled them and ran the truck, it was a little better. I took a closer Look and noticed the ones I had (tip was rounded with what appeared were small slots in the tip) were different than the more squared off tips which have small holes in them. I purchased ac deco O2 sensors (more squared tip) and installed them. Truck ran much better. I still have the multiple engine misfire code, knock sensor one low voltage and 0650 mil. I also now hear a distinct ticking noise (electrical) noise coming from the coil injector area. Also, truck is very sluggish when I drive it. Most likely due to the Aforementioed codes. Thanks to everyone who has responded. Gonna keep looking.
So even more of an update. The previously codes remain. I have ordered ac delco knock sensors and I will check the intake for warpage and possible leaks when I replace the sensors. What I found really interesting was this; as I checked the fuel injector wires with the noid light, I came to injector 5. If you remember, I mentioned hearing a ticking noise on the drivers side of the engine. I checked injector 5 and as i removed the actual plug from the injector, the ticking noise stopped. Once the injector was reconnected, the noise started again. The noid light did function on 5. My guess is either an injector that's not working at all or dumping fuel. I'm guessing the latter. Any input is appreciated.
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