4.9 engine
Thread Starter
|
New User
Joined: Nov 2012
Posts: 9
Likes: 0
4.9 engine
Since I replaced the computer and did a top end overhaul on my 93 e350, the engine wants to race for about 30 seconds and then settles down and runs normally. This only happens when the motor is cold. Any suggestions as how to fix this would be welcome. Thanks
Fleet Mechanic
Joined: Nov 2011
Posts: 1,823
Likes: 43
From: New York
Do you still have the old PCM? Might be worth swapping that back in, just to be sure the new one isn't the "problem". Does it have the same catch-code as the original?
Otherwise, check for vacuum leaks.
Otherwise, check for vacuum leaks.
Lead Driver
Joined: Feb 2003
Posts: 8,140
Likes: 4
From: Oak Harbor, OH
That's about normal. When cold the computer will raise the idle and dump in a little more fuel until the combustion chambers warm up. I wouldn't worry about it. It's not going to hurt the engine. Our 302 in an 88 E150CW ran for over 300k miles doing just that.
Senior User
Joined: Dec 2010
Posts: 253
Likes: 0
My '96 4.9 NEVER idled fast for more than 5 to 10 seconds, during coldest periods in the Missouri Ozarks. It was completely factory equipped; nothing had been changed out.
I think it's a function of some variables present in Input Sensing that probably causes too-long high idle: primarily Engine Coolant Temp. and Inlet Air Temp. Running engines fast wastes fuel, if you care about that. High idle auto trans engagement is tough duty for clutches & bands, somewhat. 'Course, we used to "floor" our cast-iron transmissions in neutral, then dump them in "low"! (Ha!).
If you really want to get "into" this sort of thing, start measuring the voltages the PCM "sees" from various inputs, and compare to accepted standards.
impish
I think it's a function of some variables present in Input Sensing that probably causes too-long high idle: primarily Engine Coolant Temp. and Inlet Air Temp. Running engines fast wastes fuel, if you care about that. High idle auto trans engagement is tough duty for clutches & bands, somewhat. 'Course, we used to "floor" our cast-iron transmissions in neutral, then dump them in "low"! (Ha!).
If you really want to get "into" this sort of thing, start measuring the voltages the PCM "sees" from various inputs, and compare to accepted standards.
impish
Trending Topics
Senior User
Joined: Apr 2012
Posts: 425
Likes: 1
From: Fort Worth, Texas
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Fleet Mechanic
Joined: Nov 2011
Posts: 1,823
Likes: 43
From: New York
FWIW, I doubt he's using a '96 MAF PCM with a speed density configuration - I'm not sure if that would even start. But there may have been subtle changes to the calibrations in the speed density years (the majority of the 4.9's), and that could be what he's seeing (and as others have suggested, that wouldn't be an issue).
Thread
Thread Starter
Forum
Replies
Last Post
whitesdford
1999 - 2003 7.3L Power Stroke Diesel
4
Jan 23, 2006 03:40 PM