2000 Ford E-Series Van High RPM at idle

MPREUSS1

MEMBER
2000 FORD E-SERIES VAN
5.4L
V8
RWD
AUTOMATIC
156,000 MILES

Performed light overhaul and replaced seals and re installed in vehicle. Everything checks ok but very high idle speed (about 1700rpm). Replaced IAC and checked TPS (normal). MAF sensor cleaned and also checked normal, but I can't be absolutely sure since this is 6 wire MAF but all engine off voltages are normal. No error codes. If I restrict the air from the rear of the intake manifold to about 50% the engine returns to normal idle.
Checked for vacuum leaks 20 times but cannot find any. Seals replaced in intake manifold when I pulled engine.

4 Replies

TY ANDERSON

MECHANIC
719 POSTS

If you have access to a scan tool that will read live data tell me what the fuel trims are the short term and long term fuel trims? It sounds like you have a vacuum leak to me. Watching fuel trims will indicate weather the engine o2 sensors are reading lean or rich mixture.
During light over haul what was done to the engine?

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Tuesday, May 20th, 2014 AT 11:54 PM

MPREUSS1

MEMBER
3 POSTS

Replaced engine seals but did not pull heads: oil pan, timing chain cover, valve cover, valve seals, exhaust manifold seals, replaced all exhausted studs and nuts, new water pump, new belt tensioner and idler roller, IA new, replaced much of tubing on transmission cooling lines, flush radiator, new coolant hoses upper and lower.

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Wednesday, May 21st, 2014 AT 11:42 AM

MPREUSS1

MEMBER
3 POSTS

Finally figured out that one of the vacuum leads was installed incorrectly. Removed TB and cleaned and replaced PCV (partially plugged). Engine fired up and ran perfectly. We took for test drive and it has more power and pep than it has in a long time. Very smooth and quiet now.

Thanks for your help and suggestions.

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Wednesday, May 21st, 2014 AT 8:00 PM

TY ANDERSON