'99 Expedition XLT
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'99 Expedition XLT
Hello everyone I'm new to the site and was wondering if you guys& gals could help out with some knowledge about the trouble codes P0302, P0304, P0420, P0171, and P0174. I know at least 2 codes are misfires, courtesy of google, but the others have brought about several different answers. Truck has started to idle and accelerate very roughly. All info and recommendations are greatly appreciated.
Cargo Master
Joined: Jul 2005
Posts: 3,495
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From: Not as far west as I want
Test the coil packs on those with the misfires. I took mine in to a mechanic last week. I had three coil packs replaced, new intake gaskets installed and new throttle postition sensor installed. No more codes.
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I'll have to look into the coil packs then. I've had the truck bout 2 years and had no issues until recently and don't really know when the last major service was other than oil changes, etc ,etc....how much did that run you? If i may ask
Laughing Gas
Joined: Oct 2005
Posts: 1,226
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From: The OC
For the P0171 and P0174 both banks lean, check the rubber elbow at the back of the intake manifold coming from the PCV valve and check around for any other vacuum leaks. You should try cleaning your MAF sensor too. The misfire codes are cylinder specific. The P0420 is probably from the misfire, but get under the truck and check your O2 sensor wires and connection anyway.
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