AnthonyTE18

i have a 99 f150 with the 5.4 and it seemed like at 190000 all the coil packs started misfiring...they were replaced at 114000...all i did was replace the spring and contacts and it made a huggee difference seeing as i only paid 80 bucks for the whole new set rather than 260 for decent ones...and the performance made a huge difference

Mr.Philadelphia

You can test for cold and hot resistance readings on the coils. Again, in my experience, OEM units will last a very long time. I've seen people toss dozens of good coils that only needed cleaning or new boots and springs. Really, it's the rubber boots and fatigue and/or corrosion on the springs that are the most common failure modes on these parts. The OEM coils are decent quality. I just hate to see people throw perfectly good parts (and their money) away.

Misfires can also result from injector failure or a vacuum leak. Ideally, you would plot short term and long term fuel trims in order to make a sound diagnosis. Often times, people just throw parts at a problem without proper diagnosis, and the COPs are the easiest culprit to replace. Sometimes, the process of connecting and reconnecting the injectors and/or COP "fixes" the problem, and not the new COPs.

gforceman

Installed new cops more power runs a butt load better at wot. But still have a slight rough idle what next

Mr.Philadelphia

Easiest and cheapest thing to try would be to clean your throttle body and IAC valve with some intake cleaner or dechlorinated brake cleaner.

gforceman

i did clean the throttle body on the truck but will remove this time , where is the IAC located on this motor

Mr.Philadelphia

Standing in front of the vehicle, it's bolted to the throttle at 11 o'clock. It's up against the firewall on the passenger side and attached to the throttle body with two 8mm bolts. Be careful not to lose the washers as you remove the bolts.

gforceman

Thx appreciate.

Mr.Philadelphia

Oops, I just gave you some outdated info. for IAC location for older 5.4 L engines.

The newer V8s have what they call throttle body motors with integral IAC valves controlled by the computer. It looks like motor actuates the butterfly but the IAC plunger works more or less the same way as they did on older cable operated throttle bodies.

On my truck, it's on the right (passenger) side of the throttle body with the throttle position on the opposite side, but I have a 4.6L. Yours may be reversed.

I've not had to take mine apart, but here's a thread with photos on a 5.4:
https://www.f150forum.com/f72/how-cl...ody-maf-75006/

It doesn't show you how to remove the motor and/or IAC but it's not that hard. The IAC is the little cylinder with a plunger inside. If the gaskets look bad, you may want to put a light coat of RTV on them to make sure things are air tight.

It goes without saying that you should disconnect the negative battery terminal before starting this work. After you're finished, let the engine idle at operating temperature for 1 minute for the computer to recalibrate.

Mattstruck

if you are experiencing the CEL flash on WOT you want to check the cats as well, since you mentioned you were misfiring. Mine had a Stutter in low rpm on acceleration that was fixed by new plugs, but at WOT it would "chokeout" and CEL would flash...new cat was the resolving factor..I just dont want you to chase a problem while omitting some factors that could cause the CEL flash on WOT...