Hello. I am new to the site and searched you out to see if I can get help in fixing my bit of trouble. I hope this is the right forum to use, if not please redirect it. Thanks. Now the problem:
1996 F150 5.0 EFI auto 2WD. For several months now while driving, there seemed to be a bit of lag/hesitation/roughness and lack of power in a static pedal position. Say cruising at 55. However, if I push the gas pedal down to accelerate then power returns. Certainly a fuel economy robbing situation.
The other day while driving home, it began to have continuous roughness and no idle at all. At a stop sign I had to feather the pedal to keep it runing at all. Barely made it home. The truck will not really start. Feathering the gas pedal while trying to start the truck will result in a rough start like it is running on 2 cylinders with lots of coughing and sputtering. One time I got it to revup and as long as I kept the RPM's up and feathered the pedal, it would race. But again, let off the gas and it immediatley dies.
I'm thinking something in the throttle controls, fuel injectors, etc.
I could use a new fuel filter so I thought I would start there. But there is definitely a real problem. Help!!!!

 

I would start around the egr valve and the idle speed motor.

 

Thanks. I see you are a master mechanic is that right?
I wish you had a pic or two. Not sure where each is nor how to test them.
However, I learn quickly. If they are not too expensive, I couuld just R&R them. ??

 

I would start by not throwing parts at it. That can get expensive in a hurry. Get a scan tool, or someone with a scan tool check the computer for codes. If it's running that badly, OBD-II will most likely have a complaint and will most likely point you in the direction of the problem and will keep you from buying a bunch of parts you "think" or someone "said" might be bad that are just fine.

 

Ditto to what Eric has posted. Get your hands on an OBDll scan tool and find out what codes have been thrown to and stored by the computer. Unless you have something really obvious, like fuel dripping from the fuel regulator, then you will probably end up throwing a large whack of $$$$ without even knowing if you are on the right track. Get the codes and post back with them if you need them interpreted.

Cheers!

Mike

 

I agree, The proper thing to do is full diagnostics. Get your codes read(if there is any) The codes will direct you in a particular area. Do not assume the codes are the final word in diagnostics, after retrieving any and all dtcs, then perform circuit tests to verify proper vref-signal return-and ground. You will need to get hold of a pced for reference material. After proper diagnostics, you can effect repair (or due to the symptoms you have mentioned, remove and clean or replace the iac motor-which in my experience is more often than not the culprit) The iac motor is mounted with 2 screws on top of the engine around the throttle body (about 3 to 4 inches long, and 1" round)

 

Ok, sounds good. I will see what I can do about getting a codes reader-OBD-II.
I have never used one before but I can learn.
I will post back here if I run into trouble.. Thanks all.

 

If you plan to keep the truck for a while the investment in tools and manuals is well worthwhile.
Roger

 

Thanks everyone. I followed the advice here and got a fair deal off e-bay for an OBDII reader. Followed the directions with the unit and have a "0" for the code. Tested it again and same result. There are no codes from the OBD computer.
I will now follow the advice from vloney here. I was wondering if there is a picture or diagram of the above mentioned part, the iac motor. I also was wondering if the fuel filter ( under the drivers side rail I think ) being clogged or old could be a factor. The engine starts but then immediatly dies like it just isn't getting any fuel??
Would it be wise to replace both these parts ( fuel filter and IAC motor) as a place to start??
Brad

 

OK. I found the IAC valve. Is there any trick or special tips to replacing it? I found the part available on line from Advance auto parts for a better price than from Ford.
Anything I should know before I dig in ?

 

Before you replace it check a couple of things. With the connector removed you can test the resistance of the valve with you multimeter. It should be between 7-13 ohms.Remove it from the throttle body and clean off the carbon deposists with intake spray or carb cleaner where the pintle sits and check to make sure it is free to move in and out. A new gasket should be used when re installing it. At the harness connector check for voltage. It should be the same or close to battery voltage with the key on and engine off. My manual goes up the a 1993 so I am not sure if everthing I have said would apply your vehicle . Can you describe the starting and stalling in more detail.Will it run if you step on the gas pedal , is it hot or cold etc.

 

Good advice but I have already purchsed the parts since it seemed to make reasonable sense that this part ( IAC) could likely be the trouble. I will change the fuel filter as well since it is needed and cheap. Is changing the IAC as simple as removing the two bolts and cleaning the gasket surface? That would be nice. Should I use a good silicone sealer with the new gasket?
The truck is cold. The engine starts for about 2 seconds; starts to rev up; then dies immediately. It is as if fuel seeped in but not enough to keep the engine going. This is what it does now.
The original problem is as described earlier. Truck performing fine except no real cruising idle, seemed rough with lack of power while trying tomaintain a constant speed unless I depressed the accelerator some. Like this for several months. Then on the last drive, going fine, then rough at any speed, happened all of a sudden; could feather the pedal to keep it going, sort of, just about ready to die. Limped home and there she is, with the current problem. Switch is on front tank which is full. So the IAC valve advice given to me here seemed likely. Engine has 146K miles. Everything else working great until this. I also purchased the fuel line disconnect tool cheap enough so as to change that fuel filter, and I will put on a new serpentine belt in the process. Those two things were the only known maintenance items needed. The parts should be here in a few days. If this doesn't work, what next?

 

It's that simple. I would just install the gasket dry. It will make it easier to get off and to get the surfaces clean should you ever have to take it off again in the future.

 

I am with EPNC... and would install it dry also. It is simple to replace. My concern is that you are going to start throwing parts at it. Be carefull as without checking things out you are guessing. Lets us know how you make out.
Roger

 

Thanks guys. I will install it dry. I do agree and understand about throwing parts at it but I followed the advice and bought the OBD 2 reader and get no codes..
So the computer is not currently registering any problems. I cleared the computer and re-did the test. Still "0". No code.
So the advice I got was that the most probable culprit was the IAC valve.
I definately let you know how it turns out. I got the parts on order at good prices with free shipping. Should be here in 5 days.
I sure appreciate folks chiming in and helping with this. I have already learned alot here. Actually kind of enjoying the learning process, but not the $ cost..