Wanted to share in hopes of helping someone
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Senior Member
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From: Ventura, California
Wanted to share in hopes of helping someone
I have had a problem with my truck that has been getting progressively worse. I recently posted the following in the iATN forums:
I received several replies and suggestions, but most centered around the injectors needing to be cleaned. I don't have a professional injector cleaning system, and couldn't understand why clogged injectors would affect idle and off idle, but the truck ran great with a little more throttle.
Well, they were right, and I was wrong. I bought 2 large bottles of injector cleaner, and added them to each tank, when they were both about 1/4 full. After driving for just one day on the first tank, the problem has almost completely gone away. I plan to run the second tank, as sort of a second cleaning, in the next day or two, which I imagine will clear things up for good.
In the past, I have been firmly against the use of fuel additives for cleaning injectors, but my truck is living proof.
Just thought I'd share.
Take care,
~Chris
1995 Ford F150, 4.9L, 5 speed, OBD I, speed density, 70k
miles.
Vehicle has been tuned with known good parts, timing is set
to 10* BTDC. Knock sensor, IAT and TPS have been replaced
within 10k miles. Vacuum at idle is 19". Fuel pressure is
within specs, and holds after the key is turned off.
When cold, after the idle settles, there is an occasional
miss. There is no set rhythm to the miss. It progressively
gets worse, but has never stalled the engine. Off idle,
more pronounced when cold, but present when warm, too, it
will stumble. The best way I can describe it when it is at
it's worst is like someone driving a stick for the first
time. It will buck unless you feather the clutch, and bring
up the rpms. Otherwise, it feels just like a bad TPS does.
Once you start to accelerate, the problem completely
disappears, until you try and maintain a low speed. Driving
at 45 mph or lower, at a steady pace, it will feel like
it's cutting out, but not nearly as bad. Honestly, most
people wouldn't even notice, but I do. If it starts to cut
out, giving it more throttle takes care of it. The truck
always pulls strong, and never shows any signs of trouble
at high speeds. Just off idle, and at a steady speed, below
50 mph.
I searched the archives, and found similar descriptions
that ended up being the injectors, but in every case, the
engine had trouble with sustaining high speeds, and that's
when this one doesn't have any trouble. I don't have a
scope, so I can't absolutely rule out fuel or ignition, but
I would think that if it were either of those, the problem
would only get worse at higher speeds.
This is my work truck, and I don't have much time to work
on it, so I have tried to research as much as possible. The
other possibilities that where mentioned in the archives
included the EGR and a bad VSS, but when I disconnected and
plugged the EGR vacuum, the problem remained the same, and
my speedometer is right on the money, and never bounces or
reads erratically. Also, the O2 harness near the battery is
perfect.
I plan to look into it a little deeper this week, and
wanted to see if this rung any bells in here first. Thanks
in advance!
miles.
Vehicle has been tuned with known good parts, timing is set
to 10* BTDC. Knock sensor, IAT and TPS have been replaced
within 10k miles. Vacuum at idle is 19". Fuel pressure is
within specs, and holds after the key is turned off.
When cold, after the idle settles, there is an occasional
miss. There is no set rhythm to the miss. It progressively
gets worse, but has never stalled the engine. Off idle,
more pronounced when cold, but present when warm, too, it
will stumble. The best way I can describe it when it is at
it's worst is like someone driving a stick for the first
time. It will buck unless you feather the clutch, and bring
up the rpms. Otherwise, it feels just like a bad TPS does.
Once you start to accelerate, the problem completely
disappears, until you try and maintain a low speed. Driving
at 45 mph or lower, at a steady pace, it will feel like
it's cutting out, but not nearly as bad. Honestly, most
people wouldn't even notice, but I do. If it starts to cut
out, giving it more throttle takes care of it. The truck
always pulls strong, and never shows any signs of trouble
at high speeds. Just off idle, and at a steady speed, below
50 mph.
I searched the archives, and found similar descriptions
that ended up being the injectors, but in every case, the
engine had trouble with sustaining high speeds, and that's
when this one doesn't have any trouble. I don't have a
scope, so I can't absolutely rule out fuel or ignition, but
I would think that if it were either of those, the problem
would only get worse at higher speeds.
This is my work truck, and I don't have much time to work
on it, so I have tried to research as much as possible. The
other possibilities that where mentioned in the archives
included the EGR and a bad VSS, but when I disconnected and
plugged the EGR vacuum, the problem remained the same, and
my speedometer is right on the money, and never bounces or
reads erratically. Also, the O2 harness near the battery is
perfect.
I plan to look into it a little deeper this week, and
wanted to see if this rung any bells in here first. Thanks
in advance!
Well, they were right, and I was wrong. I bought 2 large bottles of injector cleaner, and added them to each tank, when they were both about 1/4 full. After driving for just one day on the first tank, the problem has almost completely gone away. I plan to run the second tank, as sort of a second cleaning, in the next day or two, which I imagine will clear things up for good.
In the past, I have been firmly against the use of fuel additives for cleaning injectors, but my truck is living proof.
Just thought I'd share.
Take care,
~Chris
Senior Member
Joined: Jan 2002
Posts: 1,354
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From: Valencia, California
The only fuel additive I use is Chevron Techron but I add 2 bottles of that like once a year but I've been meaning to replace my injectors anyways, I think it might have been you that said every 100k is a good time to replace them anyways.
Good Luck bro.
Good Luck bro.
Last edited by SPROCKET_X; May 12, 2003 at 12:07 PM.
Senior Member
Joined: Jan 2002
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From: New Orleans
My truck when I first got it would hesitate bad, I thought it was the TB, so I cleaned it. It ended up being injectors and I used I think STP and it made it work perfectly. But I am going to buy bigger injectors soon, so everything is good.
Thanks for the info
Thanks for the info
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Joined: Mar 2001
Posts: 749
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From: In the shop cutting something up
I have been fighting what sounds like the same problem for a month now, but I have ran 4 bottles of cleaner. Its was no help, could my they just be bad? 
When I used the cleaner I filled the tanks and ran them very low, but you said you put it in with a 1/4 tank?
When I used the cleaner I filled the tanks and ran them very low, but you said you put it in with a 1/4 tank?
Thread Starter
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Senior Member
Joined: Sep 1999
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From: Ventura, California
Originally posted by olefafl
I have been fighting what sounds like the same problem for a month now, but I have ran 4 bottles of cleaner. Its was no help, could my they just be bad?
When I used the cleaner I filled the tanks and ran them very low, but you said you put it in with a 1/4 tank?
I have been fighting what sounds like the same problem for a month now, but I have ran 4 bottles of cleaner. Its was no help, could my they just be bad?
When I used the cleaner I filled the tanks and ran them very low, but you said you put it in with a 1/4 tank?
They aren't perfect, but I have noticed a big improvement. I have decided to replace them, however. I still don't believe that the cleaner is going to bring them to their optimum level of service, but the fact that it did make a difference convinced me that the problem is in fact due to dirty injectors. The 4.9 has a really bad history when it comes to injectors, too.
Have you checked for codes?
Senior Member
Joined: Mar 2001
Posts: 749
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From: In the shop cutting something up
Originally posted by PKRWUD
Honestly, I was taught in college that fuel additive injector cleaners are a waste of money, and that has always been my experience, except this time.
Have you checked for codes?
Honestly, I was taught in college that fuel additive injector cleaners are a waste of money, and that has always been my experience, except this time.
Have you checked for codes?
No codes, no light, (light works), just idles like crap.
https://www.f150online.com/forums/sh...hreadid=114038
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Senior Member
Joined: Mar 2000
Posts: 307
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From: Montana
Yeah, when the injectors start to get dirty, they stick open slightly. This causes an incrediable rich condition on the bottom. When you get to higher rpms the enging passes enough air to lean iit back out.
Beastie, Unless you are also putting in a chip don't waste your money on larger injectors. The truck won't run better. The o2 sensors will simply lean out the new injectors.
Beastie, Unless you are also putting in a chip don't waste your money on larger injectors. The truck won't run better. The o2 sensors will simply lean out the new injectors.
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Senior Member
Joined: Sep 1999
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From: Ventura, California
Originally posted by SPROCKET_X
Chris is it a hard project to replace the injectors on the 4.9L? Something I could do in my driveway in a day.
Chris is it a hard project to replace the injectors on the 4.9L? Something I could do in my driveway in a day.
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Joined: Aug 2000
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From: Lockport, NY USA
Beastie:
24 is too big unless you do major mods, it will run too rich because the fuel trim won't be able to compensate for that large of an injector. I have seen people run 21lb injectors though. During normal driving the computer leans them out to maintain a good fuel ratio. When you go to wide open throttle the computer goes to open loop and sprays fuel based on a table in the computers memory. If you get the right size injectors you can get a good 12.5:1 ratio which can give you more power. However you can't really richen up your engine if it has catalytic convertors on it. I wouldn't bother with bigger injectors unless you do some head work.
-Jon
24 is too big unless you do major mods, it will run too rich because the fuel trim won't be able to compensate for that large of an injector. I have seen people run 21lb injectors though. During normal driving the computer leans them out to maintain a good fuel ratio. When you go to wide open throttle the computer goes to open loop and sprays fuel based on a table in the computers memory. If you get the right size injectors you can get a good 12.5:1 ratio which can give you more power. However you can't really richen up your engine if it has catalytic convertors on it. I wouldn't bother with bigger injectors unless you do some head work.
-Jon
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Joined: Jan 2002
Posts: 1,856
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From: New Orleans
Not to worry, when I do it, I am going to get everything calibrated for it, so that my truck will work perfectly fine with the larger injectors. I might just go all out ang get the FMS 42# injectors that the Ls come with, so that when I eventually build up my engine to what I want it to be, I wont have to worry about that part of the fuel system not being able to support the hp.
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Senior Member
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From: Ventura, California
Dude, stock injectors are good up to 300-350 hp. You will NEVER need 42# injectors until you add a blower. A big blower. The money you will spend trying to calibrate your engine to work with them could buy you several sets of injectors, and still won't work. Please don't waste your money that way.
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Joined: Jan 2002
Posts: 1,856
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From: New Orleans
Well thats the thing I am going to put on a vortech and run like 12psi all the time and maybe when I goto the track change the pulley and goto 18 or something. I havent decided, but I can get the injectors real cheap fro ma friend at the Ford dealership, and Mike T. can program my chip for the larger injectors and MAF sensor with no problem. I may just get the 36# injectors, but I can actually get the 42#'s cheaper.