2004 chevy suburban flex fuel misefire

Could be a restricted injector or electric issue in injector or its command signal .

I don't think you really understand what this fault code means, it means that likely all the engine cylinders are misfiring at random no set pattern, not any particular cylinder. I would start with checking for engine vacuum leaks like the intake manifold gasket. that is all I can say since you provided no make, model or year and engine type and size information.

P1189 Buick - Engine Oil Pressure Switch Fault PO301
Possible causes
- Faulty spark plug 1
- Clogged or faulty fuel injector 1
- Faulty ignition coil 1
- Fuel injector 1 harness is open or shorted
- Fuel injector 1 circuit poor electrical connection
- Ignition coil 1 harness is open or shorted
- Ignition coil 1 circuit poor electrical connection
- Insufficient cylinder 1 compression
- Incorrect fuel pressure
- Intake air leak
PO300 is just telling you that you had a misfire.

Possible causes
- Faulty spark plug (s)
- Faulty ignition coil (s)
- Clogged or faulty fuel injector (s)
- Intake air leak
- Fuel injectors harness is open or shorted
- Fuel Injectors circuit poor electrical connection
- Ignition coils harness is open or shorted
- Ignition coils circuit poor electrical connection
- Insufficient cylinders compression
- Incorrect fuel pressure
What does this mean? Tech notes
The P0300 code means that a cylinder(s) is misfiring or is randomly misfiring. Start by checking for intake leaks, intake gaskets are common caused of multi-cylinder misfiring. If no leak are found the next step is to replace the spark plugs. If the problem persist more tests needs to be done to diagnose problem, see "Possible Causes"

You are misfiring. If you have Autozone (or similar) research your check engine light, they will come up with one or more of the following codes P0300, P0301, P0302, P0303, P0304 etc. etc.P0308. The P0300 code refers to "Random/Multiple misfires" whereas the other codes refer to that particular cylinder (last digit) misfire. The P0300 code sets when 2 or more cylinders misfire (can be the same 2 over and over, but it takes at least 2 cylinders to misifre to set that code. The others only take one misfire to set the code. Now that you know what is happening, here is how to fix....
Takes all to fire a cylinder (Fuel, Spark, Air & Timing) properly. If you have random or multiple misfires, it is likely something that is COMMON to all cylinders - like the air intake/throttle body area - throttle body can get carbon buildup and not open/close properly. Check the fuel pressure to the fuel rail(s), fuel filter clogged? When you turn your key to the "ON" position, do you hear the fuel pump turn on (whine) and then shut off? No whine, means no fuel pump. Check all fuses and fuse relays related to the fuel delivery system. Check the distributor cap/rotor for any signs of carbon tracking/arcing. Do you have good spark from coil? Check wiring for the Camshaft Position Sensor/Crankshaft position Sensor for timing issues. Finally, check compression on all cylinders. Need good compression for combustion to take place.

For a single cylinder (example Cylinder #2) - Easiest to check is spark. Pull the plug and look at it. Is it wet and smell like fuel? If so, then swap it with cylinder next to it. If the problem moved, then its the plug. If the misfire is still on Cylinder #2, then swap the plug wire (both ends). If the misfire is still on Cylinder #2, then swap the coil. (see where this is going?) If the plug is dry, then check the fuel injector for operation. Noid light tester or you can get a long screwdriver and stick one end on your ear and the other on the injector - it should make a steady, rhythmic clicking sound if it is functional when car is running. No sound? Replace. Is the plug oily? Check cylinder #2 for compression. No compression or little compression means either head gasket blown or bad/sticking valve (intake or exhaust) = big money to get fixed. Timing on one cylinder is hard to test without correct test tools. Timing is likely not a problem on a single cylinder misfire. Good luck.

code p 0300 is random/ multiple cylinders ----misfires detected ===causes ---spark plugs ---HT lead/s---injector/s---ignition coil/s---low compression---wiring
he has changed a lot for nothing
a 5 year old engine can have a lot wrong with it --so new out of a crate is no guarantee
most misfires are from injector problems
it could be a loose valve seat insert so have a compression test done if moving the injectors to new locations doesn't move the misfire

I would start with the inlet manifold gasket, these are know to break down causing vacuum leaks which can cause this issue, also check around engine for other vacuum leaks

P0300 - Random / Multiple Cylinder Misfire Detected

Possible Causes:
- Improper spark plug
- Insufficient compression
- Incorrect fuel pressure
- The injector circuit is open or shorted
- Fuel injectors may be faulty
- Intake air leak

Possible Solutions:
- Perform Injector Service
- Replaced Spark Plugs
- Replaced Injectors
- Replaced Ignition Coils

P0301- Cylinder Number 1 Misfire Detected

Possible Causes:
- Improper spark plug at cylinder #1
- Insufficient compression at cylinder #1
- Incorrect fuel pressure
- The injector circuit is open or shorted at cylinder #1
- Fuel injector #1 may be faulty
- Intake air leak at cylinder

Possible Solutions:
- Perform Injector Service
- Replaced Spark Plug #1
- Replaced Injector #1
- Replaced Ignition Coil #1

Most likely your issue is with cylinder number 1. Follow the info I have provided and you should be able to solve this issue.

The 305 code means a cylinder misfire. You could have a bad valve or a cracked cylinder head (worst case). Rent a compression tester from any auto parts store that does the tool loan program and test your compression. If ALL your cylinders are within 20% of each other, then I would check your injector pressure. I hope its something simple and cheap to repair.

You might consider replacing the cam sensor. The computer relys on this signal in order to generate spark timing.