Ok, motor heads. I have a 92 F250 with the 460ci. I put on new sparks, new ignition coils, new dist cap, new fuel filter, new O2 sensor, new EGR valve, new EGR position sensor, new EGR tube and I seafoamed the whole system (crankcase, fuel, and vacuum line) and I still have a rough idle. The truck idles really low when it's cold (near to dying), and idles odd when warm. It drives just fine, but lacks power and hesitates on acceleration. The truck died 3 times as i attempted to drive it onto a car lift, and each time it was harder and harder to restart.

It ran really good until a few days ago when I stopped at the chevron to fill up, and decided to pour in that Chevron concentrated injector cleaner. 4 hours later, i get all of this. I ran my OBD reader on it, and the only codes I picked up was the O2 and the EGR. I replaced both, but no cure.

 

Do you have a way to check your fuel pressure?

What about draining the fuel tank and then putting in some fresh fuel?

 

Remove and clean the IAC.

 

Hi, Welcome to FTE!

I second that lv2race. This can cause the identical problems you described. Also, have you checked for codes?

That's a lot easier than throwing $$$ and parts at something. Try this link for additional information on how to retrieve codes from the PCM.

Fuel Injection Technical Library » How To Run a Self-Test

 

Thanks for the welcome. I do own an OBD-1 scanner, and I replaced all that ran faults.

Sadly, I don't have any equipment to measure my fuel pressure. And how do I clean an IAC, or even find it?

 

Here's the link from another member with similar problem that I posted on how to clean it.

https://www.ford-trucks.com/forums/1...l-problem.html

Be sure and disconnect neg. battery cable from the battery for @ least 10 mins. This will allow for the PCM to clear KAM and learn new strategies, espcially if the IAC is your problem.

 

Before you measure the fuel pressure, clean the IAC per the link. This is a great write-up from the Expedition forum, but it's the same part. Very easy and won't take long at all. Good Luck and let us know how it went.

https://www.ford-trucks.com/forums/9...05.4L%20Triton

 

List the codes, by number, you got and when they were displayed, i.e. Key On Engine Off (KOEO), Continuous Memory (CM) or Key On Engine Running (KOER). It can and usually does make a difference of what the code definition really is and the resolution.

 

Alright, guys. I removed and cleaned the IAC, or what looked like the IAC, I'll attach a photo of it. But no luck, I'm still running a rough idle.


As I left my truck to idle, and shake my head at it in disappointment, I found something that struck my curiosity. I feel air puffing out of this item, it's located right above the battery, on the passenger side of the hood. Anybody know what this is? I feel as if a hose should be connected to the other end...


And I ran my OBD scanner again, aside from a "System OK" code, I also picked up two codes that should have been fixed...

 

Those codes are from CM, Continuous Memory. If you have repaired or replaced any parts you should clear the codes. They do not erase themselves. Code 42 is a usually a symptom of another issue, not a bad O2 sensor.

Typical cause of a rich code is a faulty Fuel Pressure Regulator (FPR). Most common failure mode is the diaphragm leaks fuel into the vacuum port which in turn let's unmetered fuel into the intake. Pull of the vacuum hose then inspect for signs of fuel by sight and smell. The other failure mode is too high of pressure. In either case replace the FPR.

The item you are questioning is the air pump muffler. It is supposed to have an open end and it will have air coming out under idle conditions as you described.

 

I'll have to check out the FPR, but here's a small bit of extra info. As the truck idled, I pulled my ignition coils (and shocked myself numerous times in the process haha), I noticed the idle didn't change on cylinders 1 through 4, as it did on 5 through 8.

 

Check your vacuum lines! I had that, a bad EGR valve and bad MAP sensor.

I had a similar issue to yours but, mine would die out in addition to rough idle. I ended up replacing all my lines except for the map since that one was bigger, the rest were the same size (5/32") Napa can either be bought in red in 6' increments or in black pay by the foot. My shop didn't have by the foot so I went to Autozone and bought about 25' with about 4' left over. You will need about two or three T shape fittings because at least on my 302, some of the lines use a common suction line.

Hope this helps!

 

You mentioned ignition coils (plural) before. Your truck has only one coil. Could you give us more details of what you describe as "coils"?

 

What I meant by the ignition coils, I meant the individual wires that went from the distributor cap to their cylinders, but it doesn't matter anymore. I finally got that demon motor to rumble like it should.

You were right rla2005, it was my Fuel pressure regulator. I checked my fuel pressure earlier today, and was astonished that I was pushing 98 psi. WAYYYYYYY too much pressure, so after I chain-smoked a bunch of cigarettes and drank my beers, I finally came to terms that a $20 part fixed it all. Ridiculous... but anyway, totally happy and I am very grateful for all of you guys for the help and advice

 

Glad to hear you exorcized those demons!