High RPM's, but throwing error code P0340

Tiny
SHREWDLEMMING
  • MEMBER
  • 1999 JEEP CHEROKEE
  • 2.5L
  • 4 CYL
  • 4WD
  • MANUAL
  • 142,000 MILES
Went into get a hair cut, came out and my Jeep started running at a high rpm's and was throwing three error codes; P1391, P0171, and P0340. I bought a new Camshaft Position Sensor and installed it, I also did a visual inspection of all the wires, tubes, and springs related to the problems, and I ran 1/3 of a bottle of Sea foam through the engine. After that I cleared the codes and went for a drive to burn out the rest of the Sea foam. On the drive the P0340 came back up and the high rpm's returned. I have checked the wiring and, as far as I can tell, none of my vacuum lines are broken. I did not remove the lines, just visually inspected and ran my fingers over them to feel for abnormal imperfections. I am at a loss because the P0340 is suppose to get you a rough idle, not the high rpm's. So currently, with my foot off the clutch and gas, I can idle my car along in third gear at twenty five mph.
Tuesday, September 13th, 2016 AT 4:25 PM

3 Replies

Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
The p0171 is a lean bank code probably caused by a vacuum leak that can cause a high idle.
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Wednesday, September 14th, 2016 AT 12:26 PM
Tiny
SHREWDLEMMING
  • MEMBER
  • 2 POSTS
Found a vacuum hose, hidden under some components, that had blown off. I missed it on the first two look overs that I did. Everything seems to be running fine now.
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Wednesday, September 14th, 2016 AT 6:02 PM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
Glad to hear it when you get that lean bank code it's usually a vacuum leak.
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Wednesday, September 14th, 2016 AT 6:37 PM

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