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I decided to finally bring my garage queen out for a ride yesterday. She started right up, but after about 3 min of idle time, it started to ruin very rough. Almost stalling, as if one or more cylinders were not firing. CEL came on, service traction control and REP/limp mode displayed. Fortunately, still in the drive way. I ran a basic cel scan, and it shows P0068. MAP/MAF Throttle Position Correlation. I cleared it, started the car again. Started normal, started running rough again. This time I shut the car off, left the driver door open for 2 min, and restarted the car. The cel remains on, but no limp mode.
I checked all the plug/coil wires, and the air intake maf wire. I removed the air intake assembly. It has a fairly new air filter. Less than 500 miles. No obstruction in the intake. Car sits in a heated garage, in car capsule cover from Oct to April.
The car has as long as I have owned it (3 years) always had a surging idle when moving. Up and down, slowly. 7-800 to 2500 and back. I have a 1/4 mile gravel (but smooth:-)) drive way, and always keep the car in 1st gear at idle when leaving. It will stay about 1500 -2000 rpm with no throttle application. Does not matter if the car is cool or (after a trip) warm. I have to ride the brake to keep it slow on the soft surface.
Drove the car for 5 miles. Ran just fine, except for the idle surges and the cel stayed on. Same code P0068.
I have replaced the water pump and thermostat as a precautionary mx early this spring. It still has some air in the coolant system. The gauge will jump up and down a little. Original radio was replaced, including a wiring unit from Crutchfield. It does not get driven much. On the 2nd tank of gas for the summer. All stock 2008 6 Spd. 40K miles.
BusDriverC6.....the first thing I would do is check the battery, and especially the ground underneath the battery. Little gremlins can pop up, and that's the first place I would go. Then, remove and clean the MAF Sensor with the specific cleaner spray. Because you removed (disconnected) the battery, the ECU will reset. I would clear the code once you reattach the battery cables, and then let's see what happens. You might want to do the battery and ground route first and see if that works things out. One step at a time! Let us know what you find out.
Below is the code setting criteria for your P0068…ECM is comparing throttle position and engine load and they disagree the code sets…the load or airflow rate is based on Throttle Position, Baro, Map, IAT, and RPM…if you have a scan tool which you can graph these 5 data PIDS as your driving you may see something…not an easy code to fix.
I cleaned 4 grounding points under the hood. 2 under the battery, one on each fender.
Re installed the battery….and the car started right up, with no engine code showing or in the memory.
Went out for a 45 min ride. Stopped by Autozone for some cleaning spray. Both for the maf sensor and one for the throttle body.
Car ran good, but it still has a surge at idle. In 1st gear it will chug along at 1500 rpm, with a little hesitation. At a stop with clutch pressed, it idles correctly.
just prior to a stop, decelerating in 2nd, pushing the clutch it will surge to 1500 or 2000. Then settles down again.
Tomorrow I will clean and inspect the air intake assembly.
Thank you for all the suggestions.
So this is a pretty serious code and designed to keep a runaway throttle from happening. What is saying is the MAF is seeing a different rate of flow than what the present throttle angle should be seeing as airflow. I am guessing this engine is modified and has been "tuned". You need to find someone who knows what they are doing calibrating and fix the tables correctly. You can turn it off but that is not the way to do this because then you could actually have a runaway throttle situation and the car would not shut itself down.
P0068 Car running rough and surging.
