bpardo19

I have a 1993 F150 4.9 2wd 5 speed completely stock with 206,000 miles that was bought new by my family, so this truck is very important to me. It runs great but just sometimes when I start her up and the truck will feel like its running on 2 cylinders then stall out.....UNLESS i rev her up hard a couple times then she idles back down to normal and runs like a top! I changed the plugs, spark plus wires, cap, rotor, air filter, pcv valve. Any help would be great.

jay anthony

Sounds like the idle air control valve could use a cleaning.
Just unbolt it and spray it out with some carb cleaner, don’t let any cleaner run into the electrical portion though.

Hope this helps……….

bpardo19

Thanks for the quick response. Ill try that today. So i spray the actually IAC or where it connects into the throttle body? Today it didnt wanna hold an idle. It took me four tries to finally get it running, but once its runs she purs like a kitten. I heard that erratic timing may be due to distributor wear? Any thoughts on that? Also this truck has all original parts, I assume the 02 sensor is the original since purchased new off the lot in 1993.

seano04

My 93 5.8L has a very similar issue. Rough idle at startup and then it also has been stalling at red lights but always starts right back up. I was going to look into replacing the ignition module because I've just replaced the cap, rotor, plugs, wires, etc.

Since it starts right back up after it stalls, it's leading me to believe it's not a timing issue.

Just my $0.02

jay anthony

Ya spray out the IAC its self it will probably be full of carbon,
You’ll see a plastic plunger in there it needs to move back and forth.
I just unbolt it disconnect the wire and hold it over a tin can or something,
I used Q-tips along with carb cleaner once.

If that doesn’t help you may want to try removing and cleaning the throttle body.

Both along with many other things can affect idle like that.
Personally I like too try the cheap things first.

bpardo19

Thanks alot!! I will try this asap! But what I found out today is that the rough idle/stall only happens when the engine is warm. If I drive down the road to get some food then come back home, let the truck sit for 10 minutes, come out and start it again, it does the rough idle then stalls.....This does not really happen with the engine cold. But I will try cleaning the throttle body and IAC first.

bpardo19

Another thing is the muffler is missing!! lol. It has about 1 1/2 foot of pipe missing from the exhaust where the muffler should be. It smells pretty bad and sounds like popcorn at idle....could the cats be clogged or o2 be bad which causes that startup/stalling problem. Could the o2 sensors be out-of-range with the engine hot???? Thank you for all ur help.

bpardo19

and how many o2 sensors are there....like i said before nothing but oil has ever been changed in this truck. Everything is originals from driving off the lot!

seano04

It almost sounds like possibly a fuel pressure regulator. Does it smell like gas?

My reasoning is that when the truck is running, it's able to burn out or push out the extra fuel, however, when you're at a stop, the additional oil is fouling out your plugs and causing the rpms to just putter out. Fuel pressure regulator is a pretty easy fix and only lke $20-$30. That might be worth a shot.

bpardo19

Not really, but it smells bad after the cat. It burns my eyes.