'92 Ford F-150 with rough idle(sort of)

padlikehel · #1 11-03-2009, 08:44 PM

Ok I need a little help on this one and thought maybe somebody has had this one before. This truck has the 302 roller engine in it. I bought it used with the tranny burnt up. Well I had the tranny rebuilt and started driving it while working thru the bugs.
I've got everything pretty much solved except this. The truck wants to bog whenever you have to slow down for a corner or if somebody cuts you off in traffic. It will stumble whenever you go to accelerate again. I ran a self test and the computer threw codes for the Idle Air Controller and low flow on the EGR valve. Checked them out and the IAC was bad so I replaced it. The EGR valve checks out as far as I can tell as does the EGR sensor on top of it.
I cleared out the codes both ways, started it up, and drove it for about 40 miles today. Now the truck revs way up when you first start it for about a minute then settles down to idle. At idle the engine goes from running smooth to revved up slightly and missing then back to running smooth. Ive checked all the vacuum lines and cant find any leaks. Did find an inoperative EGR solenoid and replaced it. And like before the truck stumbles.

Anybody got any idea what is causing this? Any info is appreciated

txflats · #2 11-03-2009, 10:27 PM

Is it a missfire or just a bogging down problem, easy to check fuel filter just remove and blow through it there should be no resistance. I recommend replacing every 5-10k to all my customers very cheap and best maintenance for any vehicle with an external filter.

padlikehel · #3 11-04-2009, 06:46 AM

txflats, I replaced the fuel filter and did a pressure check on the pump both static and running, and checked the regulator out all were ok. To answer your question its more of a missfire.

padlikehel · #4 11-04-2009, 07:12 AM

Sorry. For clarity, the stumble is like a bogging down. The roughness at idle seems like a missfire.

knowphish · #5 11-04-2009, 09:26 AM

Start it up, late at night, lift the hood and look for "wandering sparks". It could be a bad plug wire, ect. and it will show itself. Try to get it as dark as possible under the hood. Hope this helps!!

duck commander · #6 11-07-2009, 02:53 PM

my bet is on the plug wires had the same truck in high school, went through three sets of plug wires before i bought a good set of heavy gauge racing wires. cured it right up for good.