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Ron
Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 23821
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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I have a 1989 ford f150 with the inline 6, 4.9 engine. When

Customer Question

I have a 1989 ford f150 with the inline 6, 4.9 engine. When I get it above
JA: How many miles are on the car? Is it an automatic or a manual transmission?
Customer: when I get it above 1700 RPMs it skips and jerks real bad. I have replaced the plugs, plug wires, coiland coil wire, distributer with cap and roter button, fuel filter, fuel pump, battery and starter and last the EEC computer and it still does the same thing.
JA: Are you fixing your F150 yourself? What have you tried so far?
Customer: what I just typed
JA: Anything else you want the mechanic to know before I connect you?
Customer: no
Submitted: 7 months ago.
Category: Ford
Expert:  kalamykid replied 7 months ago.

Have you done a compression test yet on all 6 cylinders?

Customer: replied 7 months ago.
150000 miles no I have not done a compression check
Customer: replied 7 months ago.
no
Expert:  kalamykid replied 7 months ago.

The first thing you need to do will be to do the compression test so you know the health of the engine itself. You may have a valve that is not sealing off all the way.

Customer: replied 7 months ago.
The truck runs great below 1700 RPMS. If the valve was not sealing it would not run good below 1700 RPMS.
Expert:  kalamykid replied 7 months ago.

The demand for fuel and air is much higher at higher rpms. If you have an intake valve that is not sealing off, you may have that cylinders firing and the pressure back wash into to the intake burning the air and fuel at higher rpms. You have already done all the basics, now it is time to do some testing to see what is going on.

Customer: replied 7 months ago.
Just give me your opinion on the cause.
Expert:  kalamykid replied 7 months ago.

With out doing any testing there is no way of knowing what is going on.

Expert:  kalamykid replied 7 months ago.

A compression test will tell you alot about what is going on and is the starting point for the diagnostics to find your problem.

Expert:  kalamykid replied 7 months ago.

You should also do a fuel pressure test.

Customer: replied 7 months ago.
I knew this was a bad idea, lets just forget the whole thing. have a nice day
Expert:  kalamykid replied 7 months ago.

I do not have a magic ball that will tell me what is wrong. All I can do is guide you through testing so we can find and fix your problem with out spending money throwing parts at it.