Studdering problem
Freshman User
Joined: Dec 2005
Posts: 48
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From: The Rolling Rock Town
ok, on the 4.9s the iac is the smaller cylindrical sensor (about 4 inches long) located between the intake tubes and the manifold, that may be your problem. i suffered SIMILIAR problems with mine. to completely rule out your fuel thing, the 87-91s had a secondary fuel pump right beneath the drivers side seat. there is a possibility that is could be giving you problems (if it even has one).
Laughing Gas
Joined: Oct 2005
Posts: 1,226
Likes: 42
From: The OC
My 1990 4.9 had a similar problem last year, but I was able to pull a KOEO MAP sensor fault code. It got progressively worse with time to where I couldn't even keep the truck running without playing with the throttle. I knew it was the map sensor for sure when I unplugged it at the firewall and the truck purred like a kitten for a couple of minutes until the computer began to compensate for the missing sensor and truck died. After replacing the MAP senspr, my truck ran the best it ever has.
Senior User
Joined: Aug 2002
Posts: 176
Likes: 0
From: Indianapolis USA
Hello,
My '96 F150 w/5.0 v8, 4r70w auto tranny, 3.55 Traction-Lok rear has
similar problem Intermittently-no codes. New plugs, fuel filter, dist. cap
and rotor, complete tranny fluid change w/premium Mercon w/enhanced shudder protection. Intermittent & slight at all speeds---noticed mainly
when hot. The other day after acceleration to 70 mph on interstate,
shuddered so bad at constant speed, thought something was going to give,went away,
though, then back to the slight, intermittent deal... Also ran a couple
bottles of injector cleaner through it. Starts easy, idles excellent.
Seems to be getting worse little by little... Around 113,000 on truck,
bought it used and was told that "nothing had been done to it"...And
it looked like it... Other than that one time severe shudder at 70,
sounds like some of the others. Any ideas on this one ??? Thanks much.
JR
My '96 F150 w/5.0 v8, 4r70w auto tranny, 3.55 Traction-Lok rear has
similar problem Intermittently-no codes. New plugs, fuel filter, dist. cap
and rotor, complete tranny fluid change w/premium Mercon w/enhanced shudder protection. Intermittent & slight at all speeds---noticed mainly
when hot. The other day after acceleration to 70 mph on interstate,
shuddered so bad at constant speed, thought something was going to give,went away,
though, then back to the slight, intermittent deal... Also ran a couple
bottles of injector cleaner through it. Starts easy, idles excellent.
Seems to be getting worse little by little... Around 113,000 on truck,
bought it used and was told that "nothing had been done to it"...And
it looked like it... Other than that one time severe shudder at 70,
sounds like some of the others. Any ideas on this one ??? Thanks much.
JR
Thread Starter
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New User
Joined: Oct 2005
Posts: 21
Likes: 0
I started this thread and finally figured out what the problem was with my engine. I waited to make sure it was really the problem before I came back and posted.
It has been over three mopnths now and I have not had the problem come back since I did the last fix. This fix included putting a new head on the truck. I started losing antifreeze and I could smell it at the exhaust. Did a compression check if I remember and had some low readings but the part that caught my attention was one of my plugs was really rusty. When the head was off I could actually see that it was warped. I did not want to spend the money to shave the head fearing that it was also cracked. So I just replace the head. I got a good deal from a friend so I was able to get a complete head real cheap. So my studdering problem if not fixed, knock on wood.
It has been over three mopnths now and I have not had the problem come back since I did the last fix. This fix included putting a new head on the truck. I started losing antifreeze and I could smell it at the exhaust. Did a compression check if I remember and had some low readings but the part that caught my attention was one of my plugs was really rusty. When the head was off I could actually see that it was warped. I did not want to spend the money to shave the head fearing that it was also cracked. So I just replace the head. I got a good deal from a friend so I was able to get a complete head real cheap. So my studdering problem if not fixed, knock on wood.
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