slight misfire cyl.4 (cold), major misfires cyl.4,6,7 (warm)
 

10,000 miles on new goodwrench crate motor. when first started (cold) has slight misfire on cyl. 4, can't even notice but scanner shows it. drive 5-10 miles (warmed up) cyl. 4,6, and 7 misfire with 4 having the most. new plugs, wires, intake gaskets, distributor, the injectors are clean, does not lose fuel pressure. I'm stuck need some ideas

Welcome to the forum!

Now about the problem, To me it sounds like you timing is slightly off. Take a timing gun if you have one, loosen the distributor, and set it to factory specs.(Should be 0 degrees before top dead center)

What year is it? What engine size? Do you ever feel it? It is normal for the scanner to show misfires in the data. As long it is not being recorded in miss history or setting a code.

'98 Silverado Z71 5.7L, ext. cab, short bed, 4x4 You can't feel it until it's warmed up then it becomes quite apparent (jerking and sputtering) and the service engine light begins to blink. Didn't realize there was a slight misfire until the scanner was hooked up from a cold start. Starts with cyl. 4 everytime, once hot other cylinders start misfiring.

Still sounds like timing to me!

Haven't checked yet, taking a break, looking for ideas to try.

The timing on this truck is not adjustable with a light, also the distributor does not really control ignition timing. It is actually the cam sensor and is used to control injector timing. It must be set looking at cam retard in the data through a scanner. The spec is 0 + or- 2. Most of the time but not always it will set a p1345 code which is cam/crank correlation. When you prove all else is good as it seems you have there is a bulletin for installing a shim on the crank sensor. It is used to set the proper air gap for the sensor. Sometimes the timing cover warps and changes the gap. Also does it have the updated electronic injectors in it or does it still have the poppet injectors?

This sounds like close to the same issue I'm having on my '97 5.7. I replaced the injector spider with the new updated one and still having the same problem with stumble and misfire. Not saying the original poster doesn't have the same issue, but I've gone around and around the bush on mine and still no solutions.

Best of wishes philgethifi! I'll subscribe to this thread and you can check out my thread for things I've found that might be of help as well.

It has the old poppet injectors, hooked up a snap-on scanner and all eight pressurized and released, tested it twice. Also is there a bulletin number on the crank sensor shim, or can you email me a copy of the bullletin? Let me know and I will give you my email address.

Anybody have info on how to shim crank sensor, pulled it out and it is rubbing.