cidsamuth

Okay, as some of you may recall, I was complaining about a "bucking" issue when the car is cold. It happens at about 3000 RPM, and only in the first 30 seconds after cold start-up. It actually "surges," and is worse in 1st gear than 2nd (I never get to 3rd and 3000 RPM before the problem is gone).

When I took it to the dealer, they tried to blame my 4.10 gears, saying they were "confusing" the computer. Note, the problem is exacerbated when I put in the Tillman tune, but I obviously returned it to stock tune before taking it to the dealer -- the the car still does it in stock trim.

The speed shop that put the 4.10 gear in suggested that the 3000 RPM flat spot that these cars have may be worse when cold. Then, with the 4.10 gear, the resulting surge is just that much more noticeable. And, of course, with a tune in that makes the car even more responsive, the surge and resulting "bucking" is even more magnified.

So, my question to you is this: If you start your car up cold (sitting for at least 4 hours) and immediately drive it without a warm-up, accelerating slowly in 1st gear, do you have any type of hiccup at 3000 RPM? If some of you can try this for me and report back, it would be much appreciated. I realize most will not have the 4.10, but if this is the nature of the car, it should be noticeable with the 3.31 or 3.73 gear also.

And, yes, I know you should let the car warm-up as a habit, and I generally do. I'm just having trouble wrapping my head around being forced to let it warm up everytime . . . its a new car, afterall. Of course, I can probably live with the idea if this is the nature of the car, and I just made it worse by adding the 4.10 (and tune).

scapegoat

new cars don't need to warm up. just don't get on the pedal to hard until it does. i usually let the rpm's drop after starting before going anywhere and don't get on it too much for 20ish minutes of running.

however, i haven't noticed any issues at 3k at any time

cidsamuth

Yea, if I wait long enough for the RPMs to drop, then the problem is gone. And, obviously, if I don't let the RPMs climb to 3000 until its warmed up, there is no problem.

I figured this was an "open loop" problem, and the drop of the RPMs at idle was an unofficial indicator the car was in closed loop.

dmhines

I generally let the cold idle kick down before driving ... which is typically more than 30 seconds. I have 3.55's and have not had anything happen like what you describe.

bingo2

Don't have this problem now or when I was NA with Brenspeed or Tillman tune.

Rollin Thunder

I only ever had bucking in any manual car if the clutch was let out to far.

matt8998nm

same here i have 3.73s and not problem and i dont harldy ever let my car warm up before driving but i always wait 20 or so minuets before getting on it.

cidsamuth

Can some of you try it, driving it as I described? Start it cold and immediately start driving. No need to get on it, just let the RPMs slowly build past 3000 in 1st.

This will go a long way to how hard I press the dealer when I take it for service.

Adam

I've noticed this, sort of. When the engine is cold the throttle seems to be more sensitive. Be delicate with the throttle or you may cause an exponential bucking action. If you notice it start to lurch, back off the gas.

cidsamuth

I wish that was it. Instead, imagine holding your foot steady on the gas and watching the tachometer climb steadily. At about 3000 RPM, the car lunges and bucks until about 4500 RPM, then gets smooth again.