Intermittent P0300 Random Misfire and Sluggish/Jolting acceleration in stop and go traffic

[Sparksalot 0]

Hello,

First time poster.  I have a 2015 Spark (gas, automatic transmission) wit 48k miles.  I've noticed a few things with my pre-owned Spark.  First, it seems when accelerating through my neighborhood after start up, the acceleration is slow and not smooth.  This same thing happens in stop and go traffic below 15 mph.  One time, and only once, when accelerating from being stopped, I actually killed the engine and had to restart it.  

 

I didn't think too much of this until I got a CEL. I checked the code on my OBD II, and had only one...P0300 (random misfire).   On the next startup, the CEL was off and hasn't been back, although the P0300 code remains when ido my OBD II scan.

 

I've also noticed a clicking noise in the engine, which I think I can diagnosis as a noisy rocker based off this forum and YouTube videos. I'm unuclear if it's related to the misfirecode.

 

Lastly, I have intermittent A/C cooling at lower speeds mostly in town. I consider this a nuisance at this point and not my main problem.

 

Does anyone have suggestions on troubleshooting my misfire code/sluggishness or know of any TSBs involving it?

 

[Retired old Gearhead 201]

CVT is not dropping down to first gear when needed...Have the reprogram recall done?

[Bobby MSME 100]

For the computer to determine when to drop into 1st gear, there are many variables involved.

First, there are no gears to change below 40 mph. The available torque is controlled simply by position of the sliding pulley which determines apparent & effective gear ratio. I have also noticed, that at speeds below 10 mph, if I step on the gas, the pulley does not shift to that position which generates maximum torque. It is exactly similar to keep driving in 2nd gear when car has slowed down below 5 mph and driver wishes to accelerate quickly. There simply is not enough torque available to accelerate.

 

The computer program which controls sliding pulley position is affected by following variables:

 

1 current vehicle road speed

2 current engine rpm

3 how much additional load is present in the car (in addition to empty tank curb weight) *

4 gradient of the road (flat, down slope or up slope) *

5 prevailing wind load *

6 ambient temperature which affects engine performance

7 tire air pressures

8 position of gas pedal when driver tries to accelerate

9 How fast the driver pressed the gas pedal (gradual acceleration or stomped on pedal)

10 How well the engine is tuned in current state*

 

Many of above variables are available as data to the computer programmer (except those marked with *) and then she has to decide which of these variables to use in computing pulley position required.

 

The old style geared automatics have a much simpler situation. If vehicle speed drops below a certain value, change to lower gear. The CVT can be programmed to ignore everything except vehicle speed. But my guess is, the programmer is using more variables to determine how much torque is needed and the commensurate pulley position. She has all this data available from sensors, so why not use them. But that makes much more difficult to write a fool proof computer program. May be GM will spend more resources on developing a smarter computer program for the CVT situation.

 

Edited June 10, 2017 by Bobby MSME
additions

[Sparksalot 0]

I didn't know of the programming recall, but wouldn't I need to be notified before I could be eligible? 

[Mr.tozzi 66]

9 hours ago, Sparksalot said:

I didn't know of the programming recall, but wouldn't I need to be notified before I could be eligible? 

No need to be notified, call a chevy dealer service department, give them your vin and they will look up the pending recalls for your vehicle.