1983 f150 i6 4.9 stumbles at high rpm
#1
12-01-2012 | 10:21 AM
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Posts: 4
1983 f150 i6 4.9 stumbles at high rpm
New to the forum. Hoping to get some experience.
I have a 1983 F150 inline 6 4.9 300 Manual 4 speed Granny Transmission
-I have checked the timing and the advance diaphragm. (idles smoother with lines pulled and plugged but still has 'main' problem -*stated below)
-I cleaned the carb and put all new gaskets etc. (STILL LOOKING ON SOLID INFO ON HOW TO ADJUST THE EXTERIOR VACUUM & ELECTRICAL SWITCHES THAT ARE ACTUATED BY THE THROTTLE ARM)
-Tightened the intake & exhaust manifold bolts. (could still be warped/have bad gaskets, but don't know)
-New fuel filter/air filter/oil
MY PROBLEM:
* When I get into high rpm in any gear, it stumbles like hell. So basically I am forced to slightly lug into every next gear up. And this happens wether or not the vacuum lines are hooked up to the distributor or not.
Any thoughts or experience greatly appreciated.
Thank you
I have a 1983 F150 inline 6 4.9 300 Manual 4 speed Granny Transmission
-I have checked the timing and the advance diaphragm. (idles smoother with lines pulled and plugged but still has 'main' problem -*stated below)
-I cleaned the carb and put all new gaskets etc. (STILL LOOKING ON SOLID INFO ON HOW TO ADJUST THE EXTERIOR VACUUM & ELECTRICAL SWITCHES THAT ARE ACTUATED BY THE THROTTLE ARM)
-Tightened the intake & exhaust manifold bolts. (could still be warped/have bad gaskets, but don't know)
-New fuel filter/air filter/oil
MY PROBLEM:
* When I get into high rpm in any gear, it stumbles like hell. So basically I am forced to slightly lug into every next gear up. And this happens wether or not the vacuum lines are hooked up to the distributor or not.
Any thoughts or experience greatly appreciated.
Thank you
#2
12-01-2012 | 11:05 AM
Senior Member
Joined: Jun 2010
Posts: 15,301
Welcome !
Do you know if your engine has the Dura-spark II or TFI ign system on it ?
I don't know how much info I can provide , but will try. Also , you seem to be on the right track with suspecting the intake/exhaust manifold possibility. How many controls/ solenoids does it have that are affected by throttle linkage movement?
If you have some carb & choke cleaner, with the engine idling ,spray some of it at the intake manifold gasket/mountings. If there is a vacuum leak there you will notice the difference immediately.
Do you know if your engine has the Dura-spark II or TFI ign system on it ?
I don't know how much info I can provide , but will try. Also , you seem to be on the right track with suspecting the intake/exhaust manifold possibility. How many controls/ solenoids does it have that are affected by throttle linkage movement?
If you have some carb & choke cleaner, with the engine idling ,spray some of it at the intake manifold gasket/mountings. If there is a vacuum leak there you will notice the difference immediately.
Last edited by hanky; 12-01-2012 at 11:13 AM.
#3
12-02-2012 | 04:27 PM
Thread Starter
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Junior Member
Joined: Dec 2012
Posts: 4
Welcome !
Do you know if your engine has the Dura-spark II or TFI ign system on it ?
I don't know how much info I can provide , but will try. Also , you seem to be on the right track with suspecting the intake/exhaust manifold possibility. How many controls/ solenoids does it have that are affected by throttle linkage movement?
If you have some carb & choke cleaner, with the engine idling ,spray some of it at the intake manifold gasket/mountings. If there is a vacuum leak there you will notice the difference immediately.
Do you know if your engine has the Dura-spark II or TFI ign system on it ?
I don't know how much info I can provide , but will try. Also , you seem to be on the right track with suspecting the intake/exhaust manifold possibility. How many controls/ solenoids does it have that are affected by throttle linkage movement?
If you have some carb & choke cleaner, with the engine idling ,spray some of it at the intake manifold gasket/mountings. If there is a vacuum leak there you will notice the difference immediately.
Drove the truck today 50 miles, and the problem didn't cure itself.
I had used up all the rest of my carb cleaner rebuilding this one. Will have to pick up another bottle and give that a shot.
The throttle linkage inadvertently can push one, roughly 2" rod/button that is connected to an electric solenoid, and also one 1/4" rod/button connected to some sort of vacuum solenoid.
It "sputters" at 30mph+ in 3rd and 55 mph+ in 4th. Really annoying. Still any thoughts appreciated.
Last edited by ajsanteiro; 12-02-2012 at 04:29 PM.
#4
12-02-2012 | 06:23 PM
Senior Member
Joined: Jun 2010
Posts: 15,301
If it has the TFI IV system there will be a module mounted on the dist housing.
The other system has a much larger control unit that is usually mounted on the fender well.
One of the solenoids could be an anti-dieseling solenoid that allows the throttle plate to close when the ign is shut down to prevent engine run on.
The other may be to increase the idle speed when the A/C is turned on. Does the vehicle have air cond? Neither should affect the operation at the speeds in question, but worn spark plugs, wires or faulty coil could.
The other system has a much larger control unit that is usually mounted on the fender well.
One of the solenoids could be an anti-dieseling solenoid that allows the throttle plate to close when the ign is shut down to prevent engine run on.
The other may be to increase the idle speed when the A/C is turned on. Does the vehicle have air cond? Neither should affect the operation at the speeds in question, but worn spark plugs, wires or faulty coil could.
#5
12-02-2012 | 06:35 PM
Senior Member
Joined: Jun 2010
Posts: 15,301
The light just came on upstairs,
If you can ,get the spec for the float level for that carb. It should have come with the rebuild kit . If the float level is too low, the engine will starve for fuel when demand is high. Check that out. Also check the accelerator pump for providing a full squirt of fuel when accelerating.
If you can ,get the spec for the float level for that carb. It should have come with the rebuild kit . If the float level is too low, the engine will starve for fuel when demand is high. Check that out. Also check the accelerator pump for providing a full squirt of fuel when accelerating.
#6
12-03-2012 | 08:42 AM
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Junior Member
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Posts: 4
The light just came on upstairs,
If you can ,get the spec for the float level for that carb. It should have come with the rebuild kit . If the float level is too low, the engine will starve for fuel when demand is high. Check that out. Also check the accelerator pump for providing a full squirt of fuel when accelerating.
If you can ,get the spec for the float level for that carb. It should have come with the rebuild kit . If the float level is too low, the engine will starve for fuel when demand is high. Check that out. Also check the accelerator pump for providing a full squirt of fuel when accelerating.
I seem to have the "other" ignition system. Dura Spark. I had been wondering what that 'module' on the driver side fender well was. It's probably 30 years old. Are these modules known to get faulty?
The float level was measured and bent/put to spec when I rebuilt it.
As far as the accelerator pump. To check it, I just idled the engine and hit the throttle and saw a good looking spray. Anything else I can do?
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