Carbon build-up?
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Lead Driver
Joined: Aug 2009
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From: Laquey, MO
Carbon build-up?
I just pulled the lower intake off my '87 F150 4.9L EFI and found a tremendous amount of carbon build-up at the end of the intake runners and around the injector nozzle. Is that amount of carbon build up typical of these engines? If not, what is likely to be the cause?
Postmaster
Joined: Nov 2012
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From: Langley, BC
I just pulled the lower intake off my '87 F150 4.9L EFI and found a tremendous amount of carbon build-up at the end of the intake runners and around the injector nozzle. Is that amount of carbon build up typical of these engines? If not, what is likely to be the cause?
Now, unless you've owned this since new you won't know your truck's full history, i.e. you don't fully know how the previous owner treated it. There are a few reasons why carbon would build up but idling is a big one.
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Lead Driver
Joined: Aug 2009
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From: Laquey, MO
I've had the truck for almost a year and haven't driven it much because of the idle problem. Previous owner(s) had swapped out the 3.55 gears for 4.10s so it either wasn't driven much or pulled some RPMs on the highway. I really don't know that much more about it other than a whole bunch of new parts had been thrown on it along the way - new radiator, starter, alternator, clutch, and a few other things I can't recall.
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Lead Driver
Joined: Aug 2009
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From: Laquey, MO
Ok - cleaned the intake runners out this morning and discovered what appear to be cracks on the bottom of 5 of the 6 injectors. The worst "cracks" correlated with the cylinders that had the most carbon build-up.
Normal wear or time to replace?
Normal wear or time to replace?
Fleet Mechanic
Joined: Nov 2002
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I think that orange donut is just a protective plastic cap to keep the injector pintle from being damaged should it ever be dropped. I do not think the cracks you show will affect the operation of the injector, assuming everything else about the injector is to spec.
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