Experience with these particular trucks is what I think this will end up taking. First a little history on this 2001 Jimmy; Since I first bought the truck it's started and ran like a champ, so well so that I only ever had to turn the key just enough to engage the starter for a split second and it would fire right up. I changed the plugs, wires, cap and rotor last 4th of July weekend or about 12,xxx miles ago as it had a noticeable miss to it. I also changed the lower intake manifold gaskets back right after the first of this year.

A couple of months ago after the Jimmy had sat unstarted or driven at work for a week (I was oncall driving the company truck) I started it to leave and I had to hold the key and crank the engine for 2-3 seconds for it to start. Now, that's really not at all a long time to crank an engine BUT it was very unusual for THIS truck as it would normally start with barely a touch, like half a second or less crank time. To this day it's still doing that. Next problem that happened about a month ago was P0410. I searched and did research on the site here and found I'll have to replace it and still need to do so but I don't think it's contributing to the most recent trouble. The most recent trouble is that earlier this week the truck threw a P0300 and is missing while at cruising speeds with no miss at all idling or during acceleration. I went through the plugs, wires, cap and rotor again all in great shape. I then checked some of the more not so obvious stuff such as the ICM, coil, distributor screens, CPS, EGR, TPS, MAF and IAT sensors as I had read in several threads on here were culprits and found no issues with any of them.

I'm at a point where I either need some help finding more items to troubleshoot or I'm just going to have to start spending a bunch of money replacing parts until I find the one culprit. While that may be one way to guarantee a great running vehicle in the end I really don't have the time or money to throw at random parts just to fix this new little problem. I feel that the longer cranking time problem and the miss are somehow related but I have NO idea how they could be related from what I've troubleshot so far.

So, anyone else have any good tips, tricks or troubleshooting techniques to try on this thing?

 

ok the po 410 has no bearing on starting or drivability. just emmisions. now the miss... i agree the 2 are connected. im gonna ?fuel a bad injector leaking down alowwing air into cpi unit causing loss of prime. try clcling the key a time or 2 then crank it. this will prime if it did leak down and should fire right up. now the miss, injectors fail and so do the regulators, all day everyday. the best easy way is to get a scan tool with datastream and a inductive pickup timing light. with this timing light in use as a spark tester u can leave running and move clamp around to check all cylinders without getting knocked on your butt. hook all up, start, CHECK AT IDLE, aim the light and watch for a skip, if u see it in the light, its ignition side, if not, and scan tool or your ear says its missing and light is steady its fuel. could be internal causing a low compression problem but unlikley. u can try to swap a plug and see if it changes which cylinder is skipping but i doubt its a plug. this is the easiest way thats thourough and anyone can do. remember cap and rotors dont last long but this test will show that too. let us know or pm me

 

I had a 99 4.3 and with the original fuel pump it always started with a quick turn of the key. I had to replace fuel pump and ofcourse stupid me used an aftermarket from advance. Ever since the aftermarket pump was in it took extra cranks to start making me think it was something else but that aftermarket pump only lasted 1 1/2 years ofcourse 6 months past warranty. Replaced the aftermarket pump with ACDelco pump and that instant start was right back. I had a bad pump right out of the box. Just another example that aftermarket can sometimes be garbage.