High RPM's, but throwing error code P0340

1999 JEEP CHEROKEE
142,000 MILES • 2.5L • 4 CYL • 4WD • MANUAL
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SHREWDLEMMING
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  • 2 POSTS
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.
Sep 13, 2016 at 4:25 PM
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SATURNTECH9
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The p0171 is a lean bank code probably caused by a vacuum leak that can cause a high idle.
Sep 14, 2016 at 12:26 PM
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SHREWDLEMMING
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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.
Sep 14, 2016 at 6:02 PM
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SATURNTECH9
  • AUTOMOTIVE REPAIR CONTRIBUTOR
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Glad to hear it when you get that lean bank code it's usually a vacuum leak.
Sep 14, 2016 at 6:37 PM