Shudder at Constant Speed- what the hell is it?!
10-28-2016, 08:10 AM
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Shudder at Constant Speed- what the hell is it?!
Hi All-
I have a 97 T100 4WD V6 3.4 manual with 285,000 miles on it. I am the original owner and have never abused the truck or done any serious off roading.
Recently when I'm at a steady speed and usually around 3,000 rpms, in 4th or 5th gear but it may happen in other gears too, the truck shudders/jerks/hesitates for a second or two and then resumes as normal. It does not happen when accelerating, only when at a constant speed which as far as I can tell is at 60mph or greater. No CEL is thrown. It feels to me like it's a misfire or quick power loss. It happens infrequently (once every 10-20 miles) and I can't do anything to create the conditions to make it happen. I THINK it's engine, not drivetrain, related but need to experience more and listen to the engine harder to see if I hear a change.
To address the condition I recently replaced all the plugs (NGK R), all the wires and coils. The plugs were worn and number three was a bit wet with gas. I did use dielectric grease to prevent arcing; I did not set the plug gaps. I was having a rough start (that would disappear after the engine warmed a bit) where it sounded like one cylinder may not have been firing but after the replacement of those items that condition has gone away.
I also replaced several vacuum lines but have a noticeable split where the air intake hose enters the throttle body- I think I sealed this split with gasket sealant and electrical tape. While there I sprayed carb cleaner in the throttle body whose outermost area seemed clean. I plan to clean the MAF and probably clean the T body a bit more thoroughly. I'll also replace the air filter for the hell of it.
Other details that may or may not be relevant:
I love this reliable truck and want to keep er running. Any suggestions you have are welcome. As I find out more about the condition I'll share my findings here.
Thanks!
I have a 97 T100 4WD V6 3.4 manual with 285,000 miles on it. I am the original owner and have never abused the truck or done any serious off roading.
Recently when I'm at a steady speed and usually around 3,000 rpms, in 4th or 5th gear but it may happen in other gears too, the truck shudders/jerks/hesitates for a second or two and then resumes as normal. It does not happen when accelerating, only when at a constant speed which as far as I can tell is at 60mph or greater. No CEL is thrown. It feels to me like it's a misfire or quick power loss. It happens infrequently (once every 10-20 miles) and I can't do anything to create the conditions to make it happen. I THINK it's engine, not drivetrain, related but need to experience more and listen to the engine harder to see if I hear a change.
To address the condition I recently replaced all the plugs (NGK R), all the wires and coils. The plugs were worn and number three was a bit wet with gas. I did use dielectric grease to prevent arcing; I did not set the plug gaps. I was having a rough start (that would disappear after the engine warmed a bit) where it sounded like one cylinder may not have been firing but after the replacement of those items that condition has gone away.
I also replaced several vacuum lines but have a noticeable split where the air intake hose enters the throttle body- I think I sealed this split with gasket sealant and electrical tape. While there I sprayed carb cleaner in the throttle body whose outermost area seemed clean. I plan to clean the MAF and probably clean the T body a bit more thoroughly. I'll also replace the air filter for the hell of it.
Other details that may or may not be relevant:
- The engine temp gauge bounces,
- I have a ripped CV boot on the driver's side but it seems okay for now (no clicking on turns),
- Slow loss of coolant- not sure where it's going but there is no coolant in oil,
- Radiator replaced ~2,000 miles ago due to a minor leak in the top,
- The shudder persisted after a recent tire balance and rotation,
- I replaced my clutch ~2,000 miles ago and have had no issues with it,
- When I replaced the clutch I lost the function of my cruise control- probably just need to rescrew/tighten the cable in the transmission,
- Alternator rebuilt by reputable shop 2,000+ mies ago,
- Sway bar bushings replaced ~2,000 miles ago.
I love this reliable truck and want to keep er running. Any suggestions you have are welcome. As I find out more about the condition I'll share my findings here.
Thanks!
