Diagnosis
Thread Starter
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Tuned
Joined: Apr 2002
Posts: 328
Likes: 93
Diagnosis
1989 F350 7.3 idi 5-spd. 4X4 4.11 gears 170,000 miles. 20+mpg
It has a miss between 50 & 55 mph. Less than 50mph, no miss. Over 55 mph, no miss. This occurs in 5th gear @ just under 2000 rpm. If it's over 2000 rpm, no miss! If you agressively accelerate from 50mph to 55mph, the miss is much less noticable.
As far as I know this engine is completely original except the injection pump was replaced / rebuilt. I am wondering if the symptoms point towards "bad injectors"??? I also replaced the fuel lines between the injectors about a year ago.
What are the recommendations regarding injector replacement? Replace one at a time or by the set like changing spark plugs? Any recommendations where to buy the injectors?
Thanks
It has a miss between 50 & 55 mph. Less than 50mph, no miss. Over 55 mph, no miss. This occurs in 5th gear @ just under 2000 rpm. If it's over 2000 rpm, no miss! If you agressively accelerate from 50mph to 55mph, the miss is much less noticable.
As far as I know this engine is completely original except the injection pump was replaced / rebuilt. I am wondering if the symptoms point towards "bad injectors"??? I also replaced the fuel lines between the injectors about a year ago.
What are the recommendations regarding injector replacement? Replace one at a time or by the set like changing spark plugs? Any recommendations where to buy the injectors?
Thanks
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
At 170,000 you are due for new injectors.
I replace all of mine at the same time.
50 to 55 MPH would be between 1700 and 1850 RPM.
That is a rather tight 150 RPM band to have a miss that is otherwise not noticable.
I replace all of mine at the same time.
50 to 55 MPH would be between 1700 and 1850 RPM.
That is a rather tight 150 RPM band to have a miss that is otherwise not noticable.
Posting Guru
Joined: Jul 2004
Posts: 1,627
Likes: 0
From: West Valley Utah
Are you certain it's an engine miss and not a drive train vibration?
I have seen many, many tires that have a vibration somewhere between 45-55 mph ever since tire shops went to the computerized balancing.
I have seen many, many tires that have a vibration somewhere between 45-55 mph ever since tire shops went to the computerized balancing.
Thread Starter
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Tuned
Joined: Apr 2002
Posts: 328
Likes: 93
If I shift from 5th down to 4th and maintain the same speed between 50 & 55, no miss. If I drop the rpm down to just below 2000 in 4th gear, miss is there but not nearly as noticable as in 5th @ >2000. I have now ran a full bottle of Lucas injector cleaner through it with no difference. I guess it's time to replace the injectors.
What are the recommendations regarding new or rebuilt. I have a friend who works at a international truck parts store. Usually gets me parts at a really good price. OR, is there an after market injector that is better???
Thanks for all the help!
What are the recommendations regarding new or rebuilt. I have a friend who works at a international truck parts store. Usually gets me parts at a really good price. OR, is there an after market injector that is better???
Thanks for all the help!
