Engine missing when at cruising speed?
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Joined: Apr 2006
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From: Alaska
Engine missing when at cruising speed?
I have been searching these threads for hours trying to pin down an answer as to why my truck "misses" (coughs, sputters, hic-up) when at cruising speeds. It doesn't seem to matter if I'm cruising in 3rd gear, 4th gear, or OD. When I get on the throttle it picks right up, no problems. I can't get it to duplicate when not driving (ie: while parked, holding the throttle at different rpms) I have read it could be anything from a vacuum leak, my TPS, IAC, EGR, fuel pump, fuel filter, etc. I have replaced the, distributor, plugs, wires, and fuel filter. It seems this is a problem with a few I6's in this forum but I have yet to find one that fixed the problem. Please help.
Viggy
92 F150,x-cab, 4x4, 4.9L, 5sp.
Viggy
92 F150,x-cab, 4x4, 4.9L, 5sp.
Tuned
Joined: Jan 2006
Posts: 290
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Did you replace the distributor rotor cap? My 85 van would not start last week. I got it started and the only thing I think I did was to clean the contact post and rotor on the distributor with a pocket knife. I might have had a loose connection some where but I don't think so. It sound electrical to me. Check for bad grounds and connections. Look at the motor at night for sparks. Look at your dist cap again. Some times they can ark between the posts and it will score the cap.
Postmaster
Joined: Dec 2006
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From: Spokane, WA
I was experiencing a similar problem but at low to moderate speeds and light to moderate throttle pressure on my '83. The Tech's that are rebuilding my engine said the problem is common and that going down 1 or 2 sizes in the EGR metering usually eleminated the problem.
Postmaster
Joined: Dec 2006
Posts: 3,603
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From: Spokane, WA
Apparently there are different sized metering parts that can go inside the EGR valve but that is all I can tell you about it. Check with an Emissions savy Tech and they can probably fill you in.
Also, I still had the problem after I had to have a new EGR valve installed to pass emissions but that was prior to talking to another Tech about the problem when he advised me about the different metering parts. In the mean time I had a Mallory HyFire 6a box installed along with a MSD Blaster 2 coil, opened the plug gap to 50 and that reduced the problem 90%+ and really woke it up.
BUT having said all that it appears you have a FI engine and mine is carbed ('83) and I am not at all familiar with the intricate workings of a FI engine.
Also, I still had the problem after I had to have a new EGR valve installed to pass emissions but that was prior to talking to another Tech about the problem when he advised me about the different metering parts. In the mean time I had a Mallory HyFire 6a box installed along with a MSD Blaster 2 coil, opened the plug gap to 50 and that reduced the problem 90%+ and really woke it up.
BUT having said all that it appears you have a FI engine and mine is carbed ('83) and I am not at all familiar with the intricate workings of a FI engine.
Last edited by Harte3; Jan 13, 2007 at 12:05 PM.
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1987 - 1996 F150 & Larger F-Series Trucks
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