Help! Trouble shooting multiple misfire code P0300 01 Chevy S10

[fwhitt]

Hello all,

I bought a 01 Chevy S10 with 4.3l. It's has a P0300 code on it and I'm trying to find the problem. I've changed all the plugs, wires, distributor cap, rotor button, changed the crank sensor and it's help but still have the code and i get random service light flashing and that i know is bad. I'm thinking the spider injector may be the problem i'm seeing multiple misfires on cylinder 1 and 4 from the history. I was wondering if you could take a look at my data file and tell me what you think? Any help would be greatly appreciated. I am very new with HP tuners but loving the capabilities so far.

[TransGo Robert]

Most likely the injector spider under the intake is plugged up for cylinder #1 and #4, it looks like they are barely firing at all.

[fwhitt]

Thank you for the reply Robert. I thought that might be the case as well. I have a spark tester coming. Before I tear down the intake I?m going to verify I?m getting fire on those two cylinders. I?m also planning to do compression test on them as well. If those pass I?ll be doing a spider injector.

[TransGo Robert]

Thank you for the reply Robert. I thought that might be the case as well. I have a spark tester coming. Before I tear down the intake I?m going to verify I?m getting fire on those two cylinders. I?m also planning to do compression test on them as well. If those pass I?ll be doing a spider injector.

Yea make sure compression is good (very doubtful if it was a compression issue since the two cylinders are not next to each other) and that you have good spark then it's going to be the usual spider issue.

[fwhitt]

Ok, thank you.

[TheMechanic]

Spiders are easy peezy to daig. Install fuel pressure gauge, hook up scan tool. energize fuel pump prime. record fuel pressure KOEO.
pulse injector one and record fuel pressure drop. Repeat for each cylinder. Most will be within a pound or two. You will find one or more that has no drop at all. Possible no sound at all also. Done so many at the dealer when they first came out I could do them in my sleep. Back before they switched to an updated multec we had to replace each poppet valved injector one at a time. We would often get the same vehicle back multiple times for different injectors until they updated with the multec at the port.