Got a stumper I need some advice on...
2007 Tahoe LT, 5.3 FFV, 287k on the clock, longblock was replaced at 200k due to AFM lifter failure, AFM disable dongle was put in with the new engine.
A couple weeks ago she developed a stumble at idle. Just a quick little stutter and then normal. Registers as about a 50 rpm drop on the tach. It's getting progressively worse as time goes on (meaning freequency between stumbles is getting higher), but there is no check-engine light or OBDII codes.
It's to the point that it stumbles every 2-3 seconds sitting at a light, and if I just ease off the brake and let it start to roll, it increases to about 0.8 seconds between stumbles (sat there in traffic with a stopwatch recording a lap at each stumble).
As soon as I give it any gas pedal, it smooths right out and does not feel low on power at any point. Occasionally, it will stumble at steady-state cruising on the freeway, but just a one-and-done kind of thing.
It feels like a missfire, but I would think the computer would recognize that?
Any advice on where to look?
2007 Tahoe LT, 5.3 FFV, 287k on the clock, longblock was replaced at 200k due to AFM lifter failure, AFM disable dongle was put in with the new engine.
A couple weeks ago she developed a stumble at idle. Just a quick little stutter and then normal. Registers as about a 50 rpm drop on the tach. It's getting progressively worse as time goes on (meaning freequency between stumbles is getting higher), but there is no check-engine light or OBDII codes.
It's to the point that it stumbles every 2-3 seconds sitting at a light, and if I just ease off the brake and let it start to roll, it increases to about 0.8 seconds between stumbles (sat there in traffic with a stopwatch recording a lap at each stumble).
As soon as I give it any gas pedal, it smooths right out and does not feel low on power at any point. Occasionally, it will stumble at steady-state cruising on the freeway, but just a one-and-done kind of thing.
It feels like a missfire, but I would think the computer would recognize that?
Any advice on where to look?