I have a '97 F-150 4.6 and I am having some problems. Last week truck wasn't running right and after checking this site I deduced the problem to be the IAC. I replaced it, as well as plug, plug wires, and fuel filter. Well the truck was running pretty good until this morning. I drove about 40 miles or so and stopped to go into a store. After about 20 minutes I came back fired her up and it was running really rough. I pulled over, shut the truck off restarted it and still have the same problem. The problem is that it only has this rough idle while in gear or driving. If the truck is in park or Neutral I don't seem to feel it. Also the check engine light was flashing while I was driving. It would flash for a while then just stay on. If I tried to speed up any it would flash again and then just stay on again. Any suggestions of where I should start to check? I sure would appreciate it.

 

Hey Chris McCabe,

Next logical check for me would be the coil packs. If you don't already have the repair/maintenance books and a digital voltmeter, they are invaluable.

There are still a hand full of other sensors that affect ignition timing and the air/fuel mixture so it may be best to extract the malfunction code from your PCM before spending anymore money on parts.

DO NOT DISCONNECT YOUR BATTERY BEFORE RETRIEVING THOSE CODES. Even if you replace parts and think that the problem is solved, it may come back in a few days and you'll need to know why the MIL came on in the 1st place.

 

Does it run really rough and shudder really bad, too? Mine is doing the same thing, and it shakes the stuff in the cupholders whenever I drive it now.

 

my 97 4.6 does the same when sitting at a red light or stop. not to the extent of shaking the cup holder though. i only have 40,00 on the truck,but it has done it for a long time. someone did tell me to disconnect the battery for 15 minutes to reset the computer but that didnt work. hope someone can figure it out

 

Check your O2 sensors, thats what the problem on my 97 4.6 was.