Early Converter Lockup When Cold?
12-09-2018, 07:16 AM
#1
On The Tree
Thread Starter
Early Converter Lockup When Cold?
Truck is a 2003 Silverado 2500HD 4x4 with 6.0 and 4L80E. Only modifications are shorty headers and an Airaid Modular Intake Tube (stock filter box). No tuning changes, that's all stock.
Title indicates what I THINK is happening. Only happens when cold. By "cold", I mean ambient temp cold and truck cold start, such as morning commute to work sub freezing ambient temp; or after sitting all day at work in sub freezing temps. What happens is this: Starting off from stop, first pulling out onto the road, so truck has been running for a few minutes, enough time to get out of the garage or parking lot or whatever, and make my way to the road. Say 1 to 2 minutes running time. Starting off easy, light throttle. Taking it easy, truck isn't warmed up yet. First shift, from 1 to 2, shifts early (because of light throttle), but seems to either already have the converter locked up, or it locks up immediately upon shifting to 2nd. RPM drops to 1300 maybe, truck sometimes "bucks". Step a little harder on the gas to try to get either a downshift or unlock the converter and it won't do either. It's clearly struggling because it's in too high a gear for the speed, load, etc.
So, what gives? Is my converter faulty? Seems normal once warmed up, this never happens at warmer ambient temps, even moderately cold, like 40's. I usually see it only when ambient temps hit the 20's, but then it happens consistently.
If I put the truck in "towing mode" this doesn't seem to happen. Any help? No check engine light or other indication of a fault.
Title indicates what I THINK is happening. Only happens when cold. By "cold", I mean ambient temp cold and truck cold start, such as morning commute to work sub freezing ambient temp; or after sitting all day at work in sub freezing temps. What happens is this: Starting off from stop, first pulling out onto the road, so truck has been running for a few minutes, enough time to get out of the garage or parking lot or whatever, and make my way to the road. Say 1 to 2 minutes running time. Starting off easy, light throttle. Taking it easy, truck isn't warmed up yet. First shift, from 1 to 2, shifts early (because of light throttle), but seems to either already have the converter locked up, or it locks up immediately upon shifting to 2nd. RPM drops to 1300 maybe, truck sometimes "bucks". Step a little harder on the gas to try to get either a downshift or unlock the converter and it won't do either. It's clearly struggling because it's in too high a gear for the speed, load, etc.
So, what gives? Is my converter faulty? Seems normal once warmed up, this never happens at warmer ambient temps, even moderately cold, like 40's. I usually see it only when ambient temps hit the 20's, but then it happens consistently.
If I put the truck in "towing mode" this doesn't seem to happen. Any help? No check engine light or other indication of a fault.
12-09-2018, 12:02 PM
#4
On The Tree
Thread Starter
if this were normal adjustments for cold temps, upshift would be delayed to keep engine rpm and egt up. This would be to help warm up catalytic converters and general engine heating. The truck is doing the opposite.
12-09-2018, 12:03 PM
#5
On The Tree
Thread Starter
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12-12-2018, 08:08 PM
#8
On The Tree
Thread Starter
No, it IS causing issues. There is no mpg benefit to a locked converter when accelerating stone cold in 2nd gear. As stated in my original post, the truck bucks and struggles to accelerate because of the early converter lockup. It puts heavy strain on the cold engine trying to lug the truck with a locked converter. "Just drive it" is not an option. This needs a fix so nothing else gets F-ed up!
