For the last 18-months, the engine will shudder when going up a slight incline or under light load. Push on the gas, I have tons of power. Gear changes are always smooth. It's when I'm on cruise control or holding the engine steady between about 1400 and 1800 RPMs. The rpms also tend to surge a bit up and down about 50-100 rpms in a regluar frequency when under this condition. Every couple months when this happens, I'll get a P030X random misfire code and the car goes into limp mode. There is usually a fuel odor and even some light smoke from under the hood. The code has been thrown for three of the six cylinders and seems to be random as to which one (1, 2, 4). After sitting for five minutes, the car runs fine. I've replaced the coils twice, the crankshaft and camshaft sensors, and all the plugs. I even sent it to the dealer a couple months ago for a week and they couldn't reproduce the problem and all their diagnostics came back OK. Did the same thing with the same results at a Firestone repair shop a couple months prior to that.
Last night, it happened again. This time, it had two new codes. I pulled the codes, cleared them, and the car's back to normal (normal being the slight shudder and surge explained above):
- P00C6: Fuel Rail Pressure Too Low - Engine Cranking (Intermittent)
- P228C: Fuel Pressure Regulator 1 Exceeded Control Limits - Pressure Too Low (Confirmed)
The parts store and I went through the diagnostics on those errors and determined next step should be to replace the high pressure fuel pump. It shows up in a couple days. Should I also try replacing the fuel pressure sensor while I'm at it? Any other suggestions? There doesn't seem to be a lot of info on doing this repair on these specific vehicles. Do I need to bleed the fuel system post repair or anything? If this doesn't solve this problem, do you have any suggestions on what to try next?
Pump arrives in a couple days and I'll post back whether it fixed the problem or not. Thanks.
Vehicle: 2012 Acadia SLT w/ 85,000 miles. All regular maintenance done consistently. I run a bottle of the techron stuff through once a month. Full synthetic oil changes.