2001 Ford F-150 engine idle

JACKLE61

MEMBER
2001 FORD F-150
5.4L
V8
4WD
AUTOMATIC
245,000 MILES

Intermittent pulsating idle, fuel pump occasionally doesn't turn on. After the engine has warmed up and driven a while I get a severe pulsation during idle. It almost seems as though it gets no fuel then gets a shot of fuel so the tach is "bouncing" up and down. Lately, twice I have had the fuel pump fail to turn on after shutting off motor. If I let it sit for a minute or two I can hear the fuel pump kick on and it will start. I know it could be one of several things but when the fuel pump started acting erratic I started to wonder. PCM? Fuel pump? MAF? Bad pump relay? What's your best guess. OH, when this first started, and still, I get a P0171 and P0174 code. Bank 1 and 2 running lean. Replaced plugs, fuel filter, pcv, cleaned MAF sensor, replaced air filter.

2 Replies

HMAC300

MECHANIC
48,601 POSTS

Your fuel pump may be failing like freezing up then going so check your fuel pressure with a gauge first. I'd bet it's on the low side and the pump need replacing.

Was this

answer

helpful?

Yes

No

Friday, January 3rd, 2014 AT 10:00 AM

BMDOUBLE

MECHANIC
1,139 POSTS

Surging idle and lean dtcs= most common failure is the pcv tube collapsing and sucking air behind the throttle body. Also check the pcm and fuel pump relays, if the check engine light does not illuminate when you try to start it the pcm relay will be in question. You can also check the voltage at the pump while having someone cycle the key. Good luck