Will knock sensors being bad cause a random cylinder misfire in a 5.3? Trucks running like ****

 

You have any OBD II codes?

 

Short answer is yes and no - the PCM uses knock sensor input to retard the timing and prevent spark knock. An intermittent or unstable signal from the sensors can affect the PCM’s ability to adjust timing correctly.

However, if the PCM determines the knock sensor signal is unreliable, it will set a code and ignore KS input until the problem is resolved (or until the next key cycle, depending on the code).

+1 with oilcanhenry on checking for codes, but FYI intermittent misfires on these trucks are most often due to loose connections on the spark plug wires. The C-clips on the wire ends are known for breaking and/or falling off - even some aftermarket wires have this issue. If your truck hasn’t had an ignition tuneup recently, I’d start with inspection of the plug wires.

 

Yes I have the p0300 random misfire and a knock sensor low input code as well. I have changed injectors new plugs changed wires out. Had 3 sets. Older ones but we’re working fine when pulled. Changed coils new intake gaskets. I have one knock sensor that ruined I know is why I’ve asked this question. But it was running like this before it threw the code too. And I have a bank 1 sensor 1 o2 showing bad as well

 

If you know a knock sensor is bad then replace it, just to make sure it’s not causing the problem.

As for the P0300, try checking the ground points for the ignition coils - they are known weak points on these engines. One is located at the right rear of the engine, near the oil pressure sensor and the other is located on the left front. Replacing the eyelets will typically resolve weak connections.

Also remove the crankshaft position sensor and inspect the end of the sensor for scratches/dents - this indicates contact with the crankshaft tone ring (normal with higher mileage). If you see any, replace the sensor and make sure to install at least one of the spacers that comes with the new sensor.

The sensor can be difficult to remove, so use penetrating oil and twist the sensor back and forth to help work it loose. I’d recommend having a new sensor at the ready as it’s not uncommon for the sensors to break even if you’re being careful.

 

iplanned to pull the crank sensor as well I have 2 other good ones laying around. That were in running motors at the time. I haven’t seen any grounds from the coils. Not an extra ground from them. Do confused there. This is the third motor in the truck. And have everything hooked up the same way as the first 2. I am now getting a p0200 code which is injector circuit open so gotta figure that out. And a map sensor code. These are both brand new as of this morning though. Well today’s scan anyways Still have o2 sensor code and knock sensor code and multiple cylinder misfire

knock sensor being bad I’ve got to get the valley pan off bc it rusted out that bad. Was that way when I got the motor

 

Please verify the year of the engine you currently have installed and if you’re using the original PCM for the truck or the engine. A mismatch between the PCM and engine controls could be part of the problem.

P0200 - Check fuses INJ A and INJ B in the underhood fuse box. If good, check for battery voltage on the pink wire at the injectors with the key on.

I’d ignore the MAP sensor code for now as it’s likely a result of the other issues.

The ignition coils have 4 pin connectors. The outer pins are the primary circuits and the inner pins are the PCM control and low reference circuits.

The pink wire should have battery voltage with the key on - the black wire should have less than 0.2 ohms resistance to block ground - any more than that is reason to suspect the ground points need attention.

To prevent false results, first touch the meter leads together and subtract that from your reading; also make sure you have a good, clean block surface for the meter lead.

 

I checked voltages to injectors all injectors are reading at 12.34 volts with key on so all seems normal with that. Although I checked both sides with voltage and idk if it’s just in the cycle but cylinders 3 4 and 7 have voltage readings around .350. The rest of them showed only .002. Does this indicate anything? I didn’t have a chance to check coils bc of rain but I have that p0200 code for open injector circuit amd I’m pretty sure it will fix my problem when I can fix that. Will a stuck injector cause that code? I changed 3 out yesterday and runs far better now. But still missing and having the 0300 and 0200 codes

the motor is an 03 and truck is 02. But all sensors and entire intake were changed. Had all the same sensors on the lower part of the motor amd all the accessories came off of my original motor.

 

The ground side of the injectors is what the PCM uses to control the pulse width. It’s normal to see minuet amounts of voltage on them KOEO. 0.002 is normal - 0.350 seems high, but doesn’t necessarily indicate problems.

If you have a noid light (or incandescent test light), use it to check for pulsing (test light will glow dimly​​​​​) while cranking.

The P0200 is a general code - if the PCM could determine which injectors are malfunctioning then it would end with the corresponding number (P0201, P0202, etc) - and is also likely responsible for (or at least contributing to) the P0300.

Without a specific cylinder(s) being identified by code, the next easiest step is to idle the engine and listen to each injector using a stethoscope. A long screwdriver or length of wooden dowel also works. The injectors should all sound more or less the same, with a clearly defined clicking noise and identical pulse. Any injectors that aren’t clicking, that sound dull relative to the others, or are clearly pulsing more slowly, should be investigated further.

 

I unhooked all the injectors one by one to find dead cylinders. Figured whichever ones didn’t change the idle weren’t firing. Had em all unplugged a day or two. Plugged em all back in and it eliminated the p0200 code at this point. Still have the misfire code. Going to pick up new plug wires shortly since I reused older ones even though they were good on other motor. And doing a compression check as well