I have a 94 F150, 4WD Automatic, over the past few months it has not been running right. It will intermitantly, but most noticebly under load, start pinging and loosing power. After a couple of hundred miles, a few of the plugs will be fouled, but I'm not sure they are always the same ones. If I can keep the RPMs above 2500 it seems to run better. I don't get any check engine lights. My most recent thought was that for some reason, while the engine is under load, the timing changes. This is bassed on my most recent trip, and while pulling some long highway hills, getting about half way up it starts loosing power and pinging. This happens all the sudden without pushing on the gas ant harder.

Thanks for any help!

 

Check computer codes
Check timing - make sure distributor is tight
Check fuel pressure
Check for vacuum leaks

 

Fuel Pressure was checked, fuel filter was replaced. The distributor is tight and set at factory specs. I was told that if I don't get a check engine light, that a code reader wont tell me anything on this motor.. Is this true??

 

I think there is a few items that is not connected to the light.
But will show on code reader. The light could also not be working correctley.
Is the air filter clean?
Have you tried a higher octane gas?

 

Yes to the air filter, it has a K+N. In my trip yesterday, I tried all three grades, I also just used one tank for the hole trip. My last trip I used the other tank. Also I noticed that when it was running ok and I would cruise about 70 mph for 20 mile. If I would do anything to disturb that, like an exit ramp, it would start acting up again.

 

umm could the coil be goin bad? have you ever replaced the idle control valve? I replaced the ICV and it cured soooo many problems i had on both mine and my uncles truck. Could it also be a clogged cat? its soo hard to tell not being able to see it.

 

I have replaced the coil, wires, plugs a couple of times, cap and rotor. I have not checked the ICV is has always idled fine, so I never looked in that direction, I will check it out. I thought of the cat, but it seems to come and go. I would think if it was the cat it would be consistant..?

 

Injector cleaner?

 

Are the plugs fouled with oil or carbon deposits?

A worn out engine will ping and valve chatter up long grades irregardless of the timing.
Might explain oil at the plugs too.

 

Good catch McLeod! I missed where he said the plugs would be fouled.

 

My '96 5.0 has been doing the same thing for a while. It pings pretty bad and seems to run bad below 2000 RPM. Mine is a five speed and if I shift into second at a low speed and give it gas it seems to hesitate a bit until it reaches 2000 RPM then it seems to clear right up. It seems to ping worse in cold weather...which makes no sense. I had my IAC replaced a while ago when the old one died. I also had my EGR DPFE? sensor replaced and that cured the pinging for about a week. I had the pickup coil and PCM relplaced also when it quit on the way to work one day. They told me both were fried but who knows. The check engine light never came on even though the truck started backfiring and belching black smoke. Wouldn't hardly run. That was around 80K miles. I have about 108K on it now. But it seems to ping worse everytime I drive it. I don't drive it often. Only about 3000 miles a year now. That's why I haven't checked into it much. If you find out anything let us know.

 

I'm having the same problem with my 92 F150, 5.0L, 4WD, E40D. We went on a 300 mile trip over the Thanksgiving weekend and here's my scenario; I’ll set the cruise at say 75 MPH with about 2000 RPM. Sometimes while going uphill, the trans. will shift out of OD as the engine load increases, as it should. I can feel the truck surge uphill with smooth power and no pinging or shuddering. Later on down the road we’ll start climbing uphill again. This time I can feel a slight drop in power just at the point where the trans. should shift out of OD. It’s almost like dropping a cylinder. The truck will start to shudder and struggle to maintain speed without shifting out of OD. I can manually shift out of OD, at which point the RPM will jump to around 3000 and the engine smoothes out. Once the engine loads decreases as we top the hill, I can hear quite a bit of pinging in the engine. If I shift back to OD too soon, the shuddering will resume and the speed will begin to drop. If I leave the trans. out of OD for 5 to 10 minutes, the engine seems to clear out and I can drop it back into OD without any shuddering or power loss. We started the trip with 87 octane fuel and Chevron fuel injector cleaner added to the tank. At one fuel stop I tried 89 octane instead of 87 with no difference in the problem. At this point I’m thinking coil or MAP sensor since those are about the only two things in the engine compartment that I haven’t touched. Or possibly the cat converter, since this only seems to happen with the engine at operating temp. Timing is currently set at 14 degrees BTDC. Any ideas or suggestions?

 

I have run injector cleaner through the tank a few times, although not recently, but it didn't seem to make a difference. The plugs a carbon fouled, it only seems to be a two of them but I'm not sure if they are always the same cylinders or not. The truck does not use any oil from change to change, there is 114,000 miles on the engine. Everything I described was in Drive, it has gotten to the point, I don't use OD anymore. At 65mph I tach about 2200 rpm.

 

I found the problem with my rough running engine. I was working on it the other day and as soon as I touched one of the plastic vacuum lines, it cracked. I ran to AutoZone and picked up about 20 feet of rubber vacuum hose. After carefully replacing all of the factory plastic vacuum lines, the engine runs nice and smooth. I’m guessing there was more than one cracked plastic vacuum line in there. They seem to get really brittle after 14 years under the hood. The rubber vacuum hose was inexpensive when you buy it in bulk. I would suggest that anyone with an older Ford truck replace the plastic vacuum lines.