Kolchakxi

My 1999 Suburban LT 4x4 7.4L w/ 89k miles is refusing to start.

I purchased it a year ago, and since then I've done pretty much all the preventative maintenance I can think of... oil changes of course, but also freeze plug replaced, new radiator, trans overhaul, front & rear diff serviced, trans case serviced, new serp belt, new master cylinder, etc. You get the idea. There isn't much that hasn't been maintained for the sake of preventative care. Battery is a 6 month old Interstate, far exceeding OEM cranking amps.

Over the last two weeks, she's started to sputter lightly while driving steady. You feel it while at various speeds, under both steady power and hard acceleration. It felt much like a miss, or water in the gas, if that explains how it appears. A few days ago, she didn't want to start... cranked normally, but would "skip" during the firing process. Finally she started, and continued the sputtering. I was hoping it was bad gas, since that's a notoriously regular thing in our isolated community. I also thought perhaps a bad fuel filter, but that was replaced about 6 months ago. Fuel pump seems to be working fine, and I haven't yet gotten close to hitting the usual 120k mileage where fuel pumps in these rigs (and pickups) tend to fail. We pulled the plugs today, and aside from being fairly ready for replacement, there appeared to be no issues. That being said, a thorough cleaning was done and the gaps were checked.

I recently had the transmission overhauled, and since she'd been occassionally sputtering prior to the trans work, I decided to have the codes checked while it was in the shop. There were no friendly secrets of issues noted by the digital detective. Nothing was found.

I was unable to find any bad relays or other issues, and the starter doesn't appear to be the issue since there was sputtering of the 454 before this episode of failure to start. So, assembled and pretty, she sits in the driveway. Myself, and 2 of my Chevy-knowledgeable buddies, are at a loss. There's no way I'm the only one that has seen this mystery... so, if you have any thoughts, I'd appreciate some input. Thanks very much.

TJ