Hi All... I recently pulled my 2002 Silverado out of storage. The truck was sitting for six years. It took some time getting the truck started. The fuel pump failed while being stored. I replaced the pump using the bed tilt method. The truck started but ran poorly. It barely held an idle until it was warm and had a hesitation at start. I ran a bottle of Sea Foam SS14 through the throttle body, added Sea Foam fuel additive, and Sea Foam Trans Tune. I drove the truck for 50 miles, and it threw a P0300 code. This is when I started my diagnosis... here were my steps:

Step 1: Changed out the spark plugs and wires (still original at 105k miles). The truck idled a lot smoother and lost some of the hesitation at start. I cleared the P0300 and drove it for 10 miles. It threw the code...

Step 2: Began ignition system diagnostics
- checked that all the connections were secure and no broken wires
- used a spark tester, and every coil threw a nice blue spark
- used a timing gun, and every coil ignited in sync
At, this point I have ruled out the ignition system

Step 3: Vacuum Pressure Test
- I pulled vacuum at the fuel pressure regulator. The regulator's diaphragm warped and had fuel in it. I replaced the regulator. The truck’s idle and start are much smoother.
- Vacuum pressure: 21Hg
- I cleared the code, but it came back! Dang!
At this point, I ruled out poor vacuum.

Step 4: Began fuel system diagnostics
- checked that all the connections were secure and no broken wires
- checked fuel pressure at idle: 52psi
- used a fuel injector tester. I turned the ignition on and bench marked the drop-in fuel pressure in medium pulse mode. All the cylinders dropped by 17psi except for cylinder 1 which dropped by 18psi.
At this point, I ruled out the fuel system.

I have not done a compression test yet. My thinking here is the P030(#) code would dictate the faulty cylinder. Am I wrong? Also, I have not done a vacuum smoke test. I think this is my next test because of the freeze frame data (attached). By no means am I an expert at reviewing this type of data. To be honest, this is the first time I’ve read such data. According to the data, the P0300 was detected at 532rpm, 193F temp, and 10.93Hg. I am not sure how a warm motor at idle can lose 11 Hg in pressure from my vacuum test in Step 2.

My gut tells me it is the manifold gasket(s), cam shaft sensor, or crankshaft sensor. Any thoughts or advice would be greatly appreciated!

Thank you much,
Dave

 

The P030# is the cylinder that is misfire. The rpm vrs. vacuum look normal, however is the idle 532 rpm? I'd suggest next step is a compression test