99 xlt 5.4
120k miles
fuel filter replaced day before yesterday
oil changed same day
fuel injector cleaner treatment the day before that

CEL came on today out of the blue

While getting my oil changed noticed the air filter gasket to my k&n was fried so I trashed it. could I be lucky and a new gasket could fix the problem?

I've read many of the threads on this topic since I had a loose pcv last time and a p0171. Oil cap is secure & dipstick as well. pcv is well seated. I cleaned my malfunctioning IAC(which was completely inoperable) a month or so ago and fixed it. It was filthy!

I'm thinking I may have partially clogged an injector or 2 with just 1 chevron fuel injector cleaner bottle. I'm sure they're dirty as hell, but don't wish to replace them if I don't have to. I'll check the pcv elbow @ the intake when the truck cools off a bit

 

The PCV elbow is a good place to start as it's very common to deteriorate. Good luck.

 

seems like there's a slight miss @ startup, until normal op temp. Even at lower rpm accelerating it's missing every now and then. Will running sea foam or something like that through my fuel system possibly clear out a partially clogged injector?

 

I seriously doubt you have a clogged injector. There is so much detergent in todays gas that injectors are rarely the culprit.

You said that your K&N filter gasket was toast. Your MAF and/or your Air Charge Temp sensor could be dirty. And if your DPFE was that bad maybe it needs to be replaced. Does the CEL flash when you experience a "miss"? How old are the plugs?

In some cases it can be your coolant temp sensor since you said it is temp related.

Just a few thoughts-

 

I put new plugs in @ 100k miles, and the "CEL" light stays on with no blinking. I've changed my #3 & #4 coils when they went out, and it's a similar type miss, not quite as harsh. It doesn't miss all the time. It will drive perfectly with a smooth idle and smooth acceleration at times.

 

What is your current code(s)?

Steve

 

p0171 bank1 too lean & p0174 bank 2 too lean. No misfire codes were present

 

Well I finally got around to replacing the pcv & hose assembly, but it doesn't look like there's a hole in the elbow where it plugs into the back of the manifold. I removed my entire TB and MAF in order to see what I was doing. They both are filthy with some type of black gritty smudge. I plan on thouroughly cleaning both while I have them off. Any other suggestions while I have these pieces off the truck? The pcv hose that goes into the side of the TB was severely worn. I pinched the hose before I ever removed it and it basically stayed pinched together. The motor still has a slight miss at start up, and at low torque acceleration (in overdrive accelerating from 50mph slowly)

 

Well I cleaned both the TB and MAF with gumout carb & choke cleaner, and installed everything back. It's idling a little rougher than usual now, but it seems to accelerate smoothly and runs fine as long as I'm not at idle. I noticed a whistling noise or hiss right when I started it the first time. The noise went away after the first 20 seconds or so. I had the hood open and I noticed a clicking noise every now and then coming from the passenger side of the motor possibly from one of my coils or injectors. Anyone have any idea what that noise could be? Sounds like an electric arc or something, and it sounds like it's contributing to the miss as it's clicking as the miss occurs.

I also believe the exhaust from the tailpipe is hotter than usual. I went back to smell the exhaust fumes to see if anything smelled strange, and put my hand near the pipe and felt the hotter than normal heat.

 

You won't necessarily hear any noise from a leaking fitting, but I assure you it's there. I've done 5-6 trucks in the last few months with P0171/P0174 and every one (4.2, 4.6 and 5.4) has been a collapsed/ripped/leaking PCV elbow.

It's easy to pinpoint it by watching the PIDS (short-term fuel trims) on an NGS.

 

Toby,

Do you mean that you cleaned the IAC and the TB? The MAF is up in the air box near the air filter???

It sounds like you still have a vac leak somewhere. And I guess you didn't do a search here on cleaning the TB because you are NOT supposed to use Carb cleaner on any part of this truck!

Coils do not make any noise. Injectors can be/are very loud. Yes you might be having an arc. Was dielectric greese used when putting the new coils on?

PCV valves can also be very loud and click/rattle when the engine is vibrating due to a bad idle.

I would go back over the job you did and make sure everything is tight and where it should be. hearing a hiss that goes away is wrong and should be found.

Just because your PCV hose didn't have a hole in it doesn't mean that it wasn't collapsing which is more common.

good luck-

 

To follow up...I got another check engine light after finishing and running the truck twice. I went to get the code read again this morning and it came back as p0136 bank 1 sensor. The idle is really iradic ranging from a bucking 600 to 1500rpms. It feels like I have a really large cam if that makes any sense. It runs and drives fine as long as I'm not at idle. I did read somewhere that I wasn't supposed to use carb cleaner on certain parts, but didn't really bother researching what areas I couldn't. There wasn't a code for p0171 & p0174 coming up this time though. The IAC was removed about a month or 2 ago and cleaned then installed back and worked perfectly. The TB and "plenom?" was removed this time. I'm not sure of the terminology there...the piece that is attached to the front of the TB with the butterfly that opens when you apply the throttle. That backside of the butterfly was crusted with some black gritty sticky mush. That's the part I cleaned with the carb & choke cleaner, as well as the entire throttle body, or the upper intake perhaps. The part that about 5 different lines go in.(gas line from near the brake booster, a line that goes from the airbox) I don't believe I placed any of those lines in the wrong place, but that could be.

 

Also, that clicking noise come to think of it could have been the pcv valve. It was coming from that general vicinity. Also the TB or upper intake (not sure which I cleaned, but I believe both) was removed from the engine prior to cleaning with carb cleaner. There is one sensor on that piece that may have gotten carb cleaner on it, but I tried to stay away from spraying that or getting it wet.

 

The hissing or whistling noise is apparent at times when I'm decelerating on the highway from 2200rpms to 1300 rpms, and it goes away when I apply the throttle. I thought it could have been from the brake booster line that I didn't secure the clamp on at the time of the installation. But I've since secured that clamp and I'm still getting the noise occasionally.

 

I've included a link to some pics of my engine compartment if that helps at all.

https://www.f150online.com/galleries....cfm?gnum=4690