OK, I just bought a new to me 1998 f150 with a 4.6 and an automatic transmission. Overall it runs well but I have noticed that in the mornings it runs much better when it’s cold and as soon as it reaches normal running temperatures it starts to lose a little power, not bad but I can notice the difference. When I run it hard out in the sand dunes I can feel it start bog down for a sec then the power comes right back again, then it bogs again…
I have also noticed it when cruising down the road at low speeds, and the engine is lugging a little bit, it will start to kind of stutter a little. Like I said, it does not happen when the engine is cold. It did make the check engine come on once but I don’t have a scan tool to see what the code was. I reset the computer and it has never come back sense.
Does it sound like an O2 sensor to anyone? Anything else I should check?
Thanks!

 

have you dont a tune up on it? i noticed the bronco i had before the fuel pump went bad it did that. it was a fuel issue. not sure why, or how but maby change the fuel filter, and give it a good tune up.

 

Ya I was planing on the fuel filter but the COPs cost a lot of cash. I just want to make sure that will fix it before I drop that much money on it.

 

a set of 8 COPS are very cheap off of ebay alot of people have had great luck with this company

http://cgi.ebay.com/ebaymotors/NEW-I...Q5fAccessories

Check them out

 

Before you do anything, make the code come back and get it scanned. You are WASTING YOUR MONEY if you do anything else first. Your computer will tell you what the problem is, there's no reason to throw money at it.

If you reset your computer, then you MUST give it time to go through its learn cycle before it will tell you what cylinder is missfiring. Get on a smooth, level piece of road and speed up to 65 mph. Then let it coast WITHOUT TOUCHING THE BRAKES OR THE GAS all the way back down to 35 mph. This will set the computer's baseline for missfires.

Put it simply...., It has to know what the normal engine noises sound like, so it listens while your are coasting (the injectors turn off) and it compares it to what it sounds like under power. That's how it detects the missfire.

There's other requirements to reset the computer, (certain number of drive cycles etc..) but they all will be accomplished with just normal driving.

 

Get a scan tool. Only replace the plugs if you think it needs them and the same for the cops. What I would really hate is to go through R&R on the plugs just to find there fresh. It’s almost as much time to change plugs as it is to put a blower on one of these engines NO BS. Could very Easley be the O2 sensors but let the scan tool tell you that first. Changing the up stream O2’s is a major pain in the butt. You have to drop the whole catalyst to do it = (

 

I just thought of something else. Your engine runs in closed loop until it gets warmed up then switches to open loop. I would bet it is the O2s but it could be a number of other things. Get the scan tool I can guarantee you will be using on other vehicle in the future and there cheap a $100 or less but a very good one is going to be around150 to 300

 

You have that backward (it runs in open loop on startup), and besides, that switch usually happens within a few seconds of startup.... Anyway, it is not likely the O2's and if it was, you would definately have a code. So... Don't replace ANYTHING without a code. And don't worry about it until it throws one.

 

Thanks for all the input. I will get the code read when it happens again and then go from there.

 

I think you have the coil pack ignition so you wouldnt need to buy cops. Wires plugs..