2002 XLT (4.6 Triton)

about two weeks ago my check engine light came on and i noticed the truck started to idling poorly after it warms up a bit.

it starts easy and then i can literally drive 2 miles and stop at a stop sign and it will start chugging and shaking and then go dead. it seems to be the worst when the engine is good and warm. i guess the reason it starts easily is that the automatic choke stays on until the engine is warm?

i've also noticed some fast idling too. for instance i can ge going 45mph down a perfectly flat, straight road and can let off the accelerator and it keep the current speed and rpm on the tach and never goes down until i hit the brake or press the accelerator again, and once again that could just be my imagination.

last week i changed the air filter and that didn't seem to make any diffrence at all.

i've noticed a slight hissing noise when i press the accelerator down in the last couple of days. the hiss seems to get higher pitched as a press the accelerator down more. this is intermittent.

i went today to Advance Auto Parts and had them do the "engine light test" and the codes that came back were:

Global OBDII

P0171
System Too Lean

P0174
System Too Lean

DTC Pending(Codes)
No Faults Detected.

i take it that means the engine isn't getting enough gas.

i've read alot on other forums where it could be the IAC Valve.

I did purchase a new fuel filter to go on there as the guy at advanced auto parts said it would be the first place he'd start.


any suggestions or advice would be greatly appreciated.
i dont have a whole lot of extra money this time of the year and would like to get out as cheaply as possible to get this fixed.

 

I would first inspect the PCV hose assembly. They are known to crack and leak at the elbows on the ends, especially the one that connects to the rear of the intake manifold.
Also, you might want to clean the MAF.

 

is that the MAF sensor?

 

The Mass Air Flow sensor. It is located in the air cleaner assembly. Open tha air filter housing and look into the side going to the engine. You will see 2 small filiments in it, spray some carb cleaner or preferably electrical contact cleaner on them. (Do not touch them, they break real easy). Let it dry for a few minutes and put the air filter housing back together.

 

i'm guessing i should unplug the positive battery cable while doing this right? and reset the computer? 10-20 minutes should suffice for the reset shouldn't it? should i clean the sensor inside the intake too?

 

It wouldn't hurt to unhook the battery and reset the computer. The IAT sensor in the intake, should be ok. It just measures the temp of the air coming in thru the intake. I pulled mine out the other day when I installed my Outlaw Power cold air intake after 68,000 miles and it was clean as new.

 

i'll be doing this saturday morning early so i'll keep you posted.

thanks for all your help.

 

No problem.

 

well, still no luck.
i pulled the positive battery cable off, took airbox loose sprayed the MAF sensor twice to make sure it was clean.

waited 20 minutes, hooked everything back up and cranked it up and it still idled horribly. i pulled out the driveway and went around the block and i noticed when i got up to around 40 mph the rear-end would jerk a bit but it stopped after a bit i think.

i still here the hissing sound. it's loud enough to hear inside the truck. it gets higher pitched i press the accelerator down..

i did check the hose that hooks to the top of the intake and goes to a small box on the driver's side. it seemed to be a bit brittle and the coating crumbled a bit when i touched and moved it a bit.

any more suggestions? this is driving me insane.

 

have you tried to replace the fuel filter or have the injection system checked and cleaned you may have clogged or non working injector / fuel injector cleaner or octane booster might help too. Keep us updated.

 

being the EFI engine nub i am, i found the pcv valve hose to be making the suckng, hissing noise, with it attached and removed from the pcv valve itself.

i took a look down into the pcv valve and it pretty bad gummed up with brown crap. i'm hoping this is the problem.

i'm off to auto zone.

 

I would clean out the IAC with carb cleaner. If you have a bad PCV valve you may have gotten some oil vapors into your intake and that usually just gums up the IAC, have you noticed any smokey start ups?

Clean all the electronic air intake connections with electric cleaner as well. You may want to try some injector cleaner also. Sometime the MAF doesn't work well if it's not strait up and down also.

 

i've changed air filter, cleaned the MAF sensor, cleaned the pcv valve, put a new fuel filter on.

well, i found the problem.
the pcv valve was good. kinda gunky but i cleaned it.
i noticed the hissing sound went away when i put my finger over the end of the pvc hose that connects to the pcv valve. i traced the hose up to the top of the back of the intake manifold or whatever it is called and found felt air sucking into it. the cheap, rubber elbow undoubtedly caved in and that cause a whole in the rubbber. i put my finger of the hole and the truck started purring like a kitten.

now i just need to figure out how to get that rubber elbow off. should it just pop off? there are two hoses connected underneath the rubber elbow that have coolant in them (one on each side) - i found out the hard way.
i hope they don't all have to come off just to replace that elbow.

anybody know? i figure the elbow is a factory part too, that will have to be bought from the dealer.

i was told the pcv valve itself has to be bought from the dealer and is around 20-30 bucks. that's ridiculous.

 

I have a 5.4l in my truck but in my mustang I have a 4.6 dohc and it only cost like 5 bucks for a pcv at any auto parts store. Yours shouldn't be anything special.

 

the pcv for my truck has one large outlet on the top and is threaded on the bottom where it connects to the valve cover with a blue gasket in the thread. all of the parts the auto parts stores had looked nothing like it.

the pcv valve isn't the problem.. it's that pesky little elbow that cinnects the pcv hose to the intake manifold.