So, this is a bit of a problem that i find insanely irritating...

i have an 87 f150 with a 300 i6 and a c6 automatic. when cold, the truck has a slight stumble when i go to take off. nothing to be concerned with (so i thought) until today, when i went to pick up mattresses from the hotel. this was the first time the truck spent a substantial time at operating temp, and oh, did it bring about some hellish things.

so, here are the NEW symptoms:
1. when cold, it stumbles coming off idle.
2. when warm, runs perfect.
3. when running warm for a WHILE, it tends to die at idle, bucks coming off idle, clears up, bucks AGAIN at around 35mph, then i lay off the gas, it shifts, and it's all clear again.

i haven't gotten a chance to run the truck at highways speeds (the fastest it's seen so far is 45mph) so i have no idea how it will behave on the highway.

things i have done to it so far:
1. brand new fuel pump and relays (Airtex fuel pump and screen, BWD relays)
2. oil change (Castrol GTX 5w30 with a Wix filter)
3. Tune up (plugs (motorcraft) wires (accel) rotor (accel) and cap (accel))
4. cleaned the throttle plates with carb cleaner
5. poured a bottle of seafoam in the gas tank monday, put premium in it today, and poured injector cleaner in it today after it started doing the evil bucking.

my friend said he could smell it was running rich, but i don't think a bad temp sensor would make it run that horribly (but, i've been surprised before).

Has anyone else had this problem? If so, have you been able to find out what it was? Because right now, I'm just about ready to bring it to a cliff, light it on fire, and give it a push (i won't, but that's how frustrated i am).

 

Pull the codes..

 

my '87 had a cracked mount on idle air valve. i didnt find it until i sprayed the outside of the valve body with carb cleaner and rinsed off some grunge and it sucked the cleaner into the cracked mount right into the airstream. so i replaced it with a new idle air valve with the elec part attached new from the parts store for under $70

 

the truck hasn't thrown on the CEL at all, but i will try to pull codes tonight. i also tried to spray cleaner around gaskets to check for vacuum leaks and found nada.

 

Something in me wants to say throttle position sensor or MAP sensor. Look up test procedures and give it a try.

 

Truck doesn't have to have the CEL on to have codes.

 

I can't really add any more input, except as others have already said;

1)CHECK THE CODES.....

2)You simply wasted money on the premium fuel...These trucks are designed to run on 87 octane...Period....

3)As stated before, after you pull the codes....Check the IAC (Idle Air Control Valve), MAP sensor, and the TPS.....Just to be sure.....

 

X2 on "CHECK THE CODES", you're just throwing parts at it without a clue as to what could be going on, see if the ECU tells you something before you waste any more $$$.

 

checked codes. dlc's: 12,13,33,77. x2 on improper idle, egr valve is for lack of better terms trash, and throttle responded incorrectly to "goose" test (my assumption, goosing the throttle, which i indeed goosed during the test and it said "operator error" (bad TPS?))

also, reason i ran premium was because here in MI, all fuel rated below premium has ethanol in it now.

oh, we ran two KOER tests, and the first time, it just showed a bad o2 sensor, and the second test it showed that the o2 sensor is good and the above were in poor condition.

truck also failed the "wiggle test"

 

Do the tests over....You shouldn't touch the throttle during the test...It'll raise the rpm's as needed...

P.S-The operator error, means YOU....Hence, OPERATOR error....Not beig a dick....Just sayin'

 

luckily for you...you are what you eat

 

Good Morning truck killers, hehehe

 

You do need to floor it when it tells you to during the KOER test. Not being a dick also. Just stating a fact bud ...

 

When I did mine...The rpm's raised themselves about 1/2 way through the test....

 

Yep, it does this also.. But when it flashes at you you need to stab the throttle or you will get another code in the mix.