Thanks so much for your help with this. I was getting fatigued talking to myself under the hood so it’s nice to have a couple other minds chewing on it. Even if it doesn’t get solved here, it is with gratitude that I read each of your suggestions and ideas.
First, a quick summary of what I messed with today and what I got as a result. This morning, I did two restarts at operating temp, each with a waiting period of 10-15 minutes after initial shutoff (ie. after I had driven somewhere and shut it off). I did it with the accelerator pedal halfway down each time and zero delay. She fired right up.
I stopped by a parts house on the way home and grabbed some Mystery Oil, figuring I’d at least get a decent cleaner headed through the fuel path. Maybe it helps, maybe it doesn’t, but it may as well be running through there while I’m trying to get to the bottom of it. Worst case, it cleans out some varnish in the injectors. Best case, that was my problem to begin with.
While at the parts house, the guy who helped me said he has a similar era Chevy that had developed the same, as he called it, a “lean start.” He swapped out the engine coolant temp sensor, which I have already done, and the air temp sensor that goes in the air intake. He said he didn’t know which one solved the problem because he swapped them both out at the same time. And he’s never seen the symptoms return.
The one in the air intake was 1996 vintage so I swapped it out for a new BWD. Then I warmed it up to op temp in the driveway for about 20 minutes, shut it off, let it sit 15 minutes. It started right up without touching the accelerator.
I had to run to the store. I shut it off, was in the store for right at 10 minutes, came back and she fired right up without touching the accelerator.
It has been probably three months now since my Burb fired up immediately at operating temp. It just did it twice in a row after changing out that air intake temp sensor. Maybe that was the issue. Maybe not. I can’t imagine that Mystery Oil could have affected a change so quickly, but I guess it’s possible. I don’t know.
I’m going to see what happens tomorrow. I’m hoping the symptoms are completely gone, but it has been such a pest to root out that I’m skeptical. I’ll be surprised if the dry-start issue just disappears and hope to be surprised. I’ll post what happens this weekend while I’m out driving around.
Rod Knox, would Mystery Oil (or some other cleaner) eventually remove carbon if it were on the intake valve stem? By “eventually,” I mean like in a few tanks of running it, not over the next decade it would eventually erode the carbon. Or at this point, as dirty as the injectors could be, is getting the injectors cleaned out by a shop sort of in order? As far as winter fuels go, I’ve been running ethanol-free for about the past 3-5k miles so fuel vaporzing shouldn’t be an issue, should it? Serious question, not being sarcastic.
oldbodyman, I spent more time combing through the service manuals last night. Found the oil pressure sensor. In the manual, it looked fairly open to get to. Under the hood, it looks like it’s sort of buried beneath a couple AC lines, which is a handy location. I’m hoping that’s not it, but until I can see if the intake sensor actually fixed the issue, your idea is still on the radar.
GeorgeSanJose, yes, there is none of that spitting. No puff of smoke, no spitting. And your comments on the manuals are true. No single section provides complete information. The GM manual parks all kinds of stuff under the chapter “On-Vehicle Maintenance/Repair,” where it offers snippets of clues that you need to make sense of the other pieces in other chapters when you can find them. I’ve had one Honda. I bought an OEM service manual for it on CD and it was absolutely intuitive and helpful. I could find and understand everything in it in a matter of minutes. And it was half the number of pages, but told me in perfect detail with very helpful drawings (that matched the steps, unlike GM’s) every single step I needed to make any repair to it. It takes me longer to locate everything in a GM service manual than it did for me to locate and finish the repairs on my Honda. I can’t even wrap my brain around the way GM does business. 15 years ago I promised myself I’d never buy another Chevy. As much as we love the utility of our Burb for our family, I’m being reminded why I promised myself that.
Thanks so much to each of you. I’ll run it around this weekend and see what happens and return with whether the issue is gone. I greatly appreciate each of you chiming in to help. Have a great evening.