Randy Lahey

Any that you would recommend?

I have roughly the same issue with my '99 Sierra 2500 6.0, 304,000kms. I rarely drive it (paid $2,500 in 2012 with 283,000kms), so I don't spend a lot on it. It was running terrible for a while where I couldn't even pass anyone on the highway as it would just bog down completely (i.e. put me over the steering wheel). I did the simple stuff first: new plugs, fuel filter, air filter (and cleaned the giant mouse nest out), cleaned the MAF sensor (with MAF cleaner), and checked the throttle body (it was clean). The plugs and fuel filter made a HUGE difference to the point that it now runs fine on the highway, no problem passing. The issue now though is that it runs about the same as it did when started up (cold)...bogs down so bad it barely moves for the first 30 or 45 seconds, then it 'catches' and runs fine from there. Idles a little rough, but not bad. It does this 100% of the time, worse in the summer (I live in Saskatchewan....+40C summers, -45C winters). However it will intermittently do the same thing when I shut it off and restart (hot, i.e. in a parking lot when waiting for my wife), chugging and bogging until it 'catches' again. I have always had an engine light showing O2 sensor, bank 2, rear, so I replaced that one and the light just came back. This was several years ago. I read that the downstream ones have no effect on how it runs, so I didn't worry about it. The engine light has since gone out (about 3 months ago) and hasn't returned. Still runs exactly the same. I do have exhaust manifold leaks, but they aren't bad. I haven't checked the fuel pressure, but I guess I could do that on startup. In my experience though a fuel pump usually just dies, but it seems maybe these GM ones can limp along forever? I was also thinking it may be the catalytic converter, but that seems like it would be an always thing, not intermittent like this. I bought a temperature sensor (cheap, GM genuine, $19) and will try that, but I don't want to start throwing parts at it. Any ideas?

Old thread, but I was wondering about this as I always keep my '99 Sierra 2500 in Auto pretty much all winter long here in central Canada. There is packed snow (and lately sheer ice from the wind) on the road sometimes from Oct to April. It's currently -36C with about 4 feet of snow in my front yard. The grader doesn't do a deep clean until spring. No such thing as 'dry pavement' in the winter here

Old thread, but I *think* I am having this issue right now on my 1999 Sierra 2500, 4x4, 6.0, extended cab, long box. I'm no expert on trannys, but I get the odd clunk/pull when it shifts from 1st to 2nd , very randomly about every 20th time I drive it (only in town). It has 297,000 kms on it, and I have no idea if the last owner ever changed it. He did swap the engine. I only paid $2,500 for the truck in 2012, and I barely drive it, but maybe I should throw a can of Seafoam in it? EDIT: I don't know that I know what 'slipping' actually feels like. I assume it's either lurching forward or hesitating when it slips, or is it just a hesitation? Mine is 'lurching' forward, not hesitating...

Took it for a drive today, about 35km each way out to my acreage, up and down hills, highway and gravel. It ran fine! Seems like it was just the fuel filter. I still find it hard to believe that it was just a $9 fix. The only other thing I can think is that maybe pulling the fuel pump relay reset something? Can that happen? New issue (old one that I notice more now) is that there is a 'shuddering' when I first accelerate from a standstill (i.e. green light). It runs fine otherwise. Maybe a u-joint? Hopefully not a torque converter issue...

I have a 99 Sierra 2500 with a 6.0L and 295,000 km. I've been having this same issue for several years now (I only drive the truck a month of the year, so I just put up with it). It takes a bit to warm up the engine otherwise it will just completely tank when I press the gas pedal more than slightly. It runs fine at speed on the highway, but starts doing the same thing when going uphill, load or not. It doesn't throw any codes. I've replaced the fuel filter, and haven't tested it uphill yet, but could it be the fuel pump?