Help with injector noise
Thread Starter
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New User
Joined: Aug 2001
Posts: 11
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From: NORTHWEST
Help with injector noise
My 1990 F150 4.9 is making some load noises that appears to be coming from the fuel injectors.
The noise get's louder as the torque increases under load.
The noise is just like a bad lifter clack, clack, clack.
At idle and free revving there is no noise at all, only under load.
Has anybody encountered this before?
The noise get's louder as the torque increases under load.
The noise is just like a bad lifter clack, clack, clack.
At idle and free revving there is no noise at all, only under load.
Has anybody encountered this before?
Elder User
Joined: Apr 2001
Posts: 772
Likes: 0
From: Glen Burnie Maryland
Help with injector noise
What your hearing is "pre-ignition" or "Spark-knock".
Tune-ups will help with this greatly.
Check your timing to make sure within specs.
Clean and re-gap plugs or replace.
Remove,clean or replace air filter.
Change brand of gas. Some brands are more prone to "knock" than others.
This is gonna get some DIRTY LOOKS but here goes.
Go to GM dealer and get some "TOP END CLEANER" (get the pour can, it's cheaper than the spray can). This stuff you pour down carb or throttle body (2/3 of can) like carb cleaner. This stuff is particularly potent so don't get it on paint. Then dump rest in, stalling engine letting the stuff soak. wait 15-20 minutes. restart engine, she'll smoke like a cold diesel for a few minutes (all or most of the crap blowing out of the combustion chamber). Run under load (drive for 15 minutes). You'll notice it will probably run smoother and not knock. Used two cans on my 87, noticed and increase in performance (doesn't strain), smoother idle, easier to start. Gas mileage went from 12 to 14. Not using as much throttle now to maintain 55.
Larry
Tune-ups will help with this greatly.
Check your timing to make sure within specs.
Clean and re-gap plugs or replace.
Remove,clean or replace air filter.
Change brand of gas. Some brands are more prone to "knock" than others.
This is gonna get some DIRTY LOOKS but here goes.
Go to GM dealer and get some "TOP END CLEANER" (get the pour can, it's cheaper than the spray can). This stuff you pour down carb or throttle body (2/3 of can) like carb cleaner. This stuff is particularly potent so don't get it on paint. Then dump rest in, stalling engine letting the stuff soak. wait 15-20 minutes. restart engine, she'll smoke like a cold diesel for a few minutes (all or most of the crap blowing out of the combustion chamber). Run under load (drive for 15 minutes). You'll notice it will probably run smoother and not knock. Used two cans on my 87, noticed and increase in performance (doesn't strain), smoother idle, easier to start. Gas mileage went from 12 to 14. Not using as much throttle now to maintain 55.
Larry
Postmaster
Joined: Jul 1999
Posts: 3,172
Likes: 4
Help with injector noise
I think what you are hearing is the Air Injection Pipe ...One of its tubes that screw into the head is broken allowing you to hear exhaust noise . It will only make the noise when the vehicle is moving .
Thread Starter
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New User
Joined: Aug 2001
Posts: 11
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From: NORTHWEST
Help with injector noise
Hello thanks for the replies.
The truck was torn down about 3 months ago and had the head rebuilt.
New lifters and all the tune up parts.
The air tube was replaced as well since it had a broken tube.
About 2 weeks ago I started to hear what I thought was a brand new lifter failing.
I started to diagnose the truck and was surprised to find the noise coming from the opposite side of the motor than the lifters. I was using an automotive stethoscope to listen.
I placed the stethoscope everywhere and found that the ticking was the same ticking as the injectors.
I had my wife let the clutch out with the park brake on until the load on the engine produced the ticking and found that the injection would get louder as more load was placed on the engine
When the truck is at an idle you can not hear the noise, only under load.
The noise that I am talking about is louder than a ping from the engine knocking.
The noise does not follow the engine rpm or make noise until there is a load on the engine.
The noise is at its loudest just before the shift points.
If you are in first gear at about 20 mph the clacking starts and get loader as you climb the rpms until you shift then the noise falls off until you push the gas pedal down for more speed then it starts all over.
In 5th gear the truck will make the noise until I can back off the gas and cruse at about 55 - 60.
Thanks again
The truck was torn down about 3 months ago and had the head rebuilt.
New lifters and all the tune up parts.
The air tube was replaced as well since it had a broken tube.
About 2 weeks ago I started to hear what I thought was a brand new lifter failing.
I started to diagnose the truck and was surprised to find the noise coming from the opposite side of the motor than the lifters. I was using an automotive stethoscope to listen.
I placed the stethoscope everywhere and found that the ticking was the same ticking as the injectors.
I had my wife let the clutch out with the park brake on until the load on the engine produced the ticking and found that the injection would get louder as more load was placed on the engine
When the truck is at an idle you can not hear the noise, only under load.
The noise that I am talking about is louder than a ping from the engine knocking.
The noise does not follow the engine rpm or make noise until there is a load on the engine.
The noise is at its loudest just before the shift points.
If you are in first gear at about 20 mph the clacking starts and get loader as you climb the rpms until you shift then the noise falls off until you push the gas pedal down for more speed then it starts all over.
In 5th gear the truck will make the noise until I can back off the gas and cruse at about 55 - 60.
Thanks again
Elder User
Joined: Apr 2001
Posts: 772
Likes: 0
From: Glen Burnie Maryland
Help with injector noise
OK.....TRY THIS ONE AGAIN.
only during load. head rebuilt. Now it sounds like a exhaust leak.
Did you use gaskets btwn the head and the exhaust manifolds??? Try tightening the Exh. manifold or replacing the gasket altogether. Make sure all mating surfaces are free of debris, burrs, chips, scars, etc....
only during load. head rebuilt. Now it sounds like a exhaust leak.
Did you use gaskets btwn the head and the exhaust manifolds??? Try tightening the Exh. manifold or replacing the gasket altogether. Make sure all mating surfaces are free of debris, burrs, chips, scars, etc....
Postmaster
Joined: Jul 1999
Posts: 3,172
Likes: 4
Help with injector noise
If you do find the exhaust manifolds leaking & use a gasket to stop the noise , be very careful tightening the intake & exhaust manifold bolts . With an exhaust manifold gasket less torque is required , the lowest torque is 22 Ft Lbs , I wouldnt tighten the bolts more than that otherwise you run the risk of breaking the ears off the lower intake because with the exhaust manifold gasket you will an uneven surfaces between the lower intake & the exhaust manifolds & the ears the bolts contact on the aluminum lower intake are very easy to break off , Even breaking one will mean buying a new lower intake . Torquing the lower intake & exhaust manifolds is hard enough .... If the exhaust manifolds are warped , Id almost rather replace them rather than add a gasket . Just remember a lower intake is going to be about $300 .
