Won't wind up
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New User
Joined: Dec 2008
Posts: 5
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From: Charlotte
Won't wind up
Long time lurker with a problem. I have a 1998 F150 4.6L auto that for some reason just won't wind up, rpm wise. I'm getting a P0306 code for a miss at low rpms in OD under load. It's also throwing an IAC over speed code, P1506. Doesn't seem to me that either would cause it to just not want to wind up. I had the P0401 problem but cleaned that out.I did put a new gasket on the IAC valve when reinstalling it. Thoughts please.
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Thread Starter
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New User
Joined: Dec 2008
Posts: 5
Likes: 0
From: Charlotte
Acts like it's starving but it has a new filter and fuel pump. I cleaned the MAF sensor wires with contact cleaner even though they weren't dirty. I sprayed around the intake & vacuum lines to see if that would affect the idle, it didn't. I pulled the plug off of the IAC valve and got no change. Shouldn't it have shut down without the IAC plugged up? If it was hung open would that cause the P1506 and the sluggish performance? It did show a P1504 after/because I pulled the IAC connector.
Postmaster
Joined: May 2003
Posts: 3,310
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From: E.Lincoln County, NC
From service manual:
CHECK IAC VALVE FOR PROPER FUNCTION
Transmission in PARK.
A/C, heater and all accessories off.
Engine at normal operating temperature and fan control off, but not disconnected.
CAUTION: Do not disconnect fan control harness. It may cause engine overheating.
Disconnect IAC valve harness connector.
Listen to engine rpm.
Did the rpm drop or engine stall?
No
NOTE: Do not attempt to clean the IAC valve.
IAC valve is inoperative, REPLACE IAC valve only. RESET Keep Alive Random Access Memory (RAM) (REFER to Section 2A, Powertrain Control Module (PCM) Reset ). VERIFY a symptom no longer exists.
CHECK IAC VALVE FOR PROPER FUNCTION
Transmission in PARK.
A/C, heater and all accessories off.
Engine at normal operating temperature and fan control off, but not disconnected.
CAUTION: Do not disconnect fan control harness. It may cause engine overheating.
Disconnect IAC valve harness connector.
Listen to engine rpm.
Did the rpm drop or engine stall?
No
NOTE: Do not attempt to clean the IAC valve.
IAC valve is inoperative, REPLACE IAC valve only. RESET Keep Alive Random Access Memory (RAM) (REFER to Section 2A, Powertrain Control Module (PCM) Reset ). VERIFY a symptom no longer exists.
