V6 F-150 no cats

[medwards29]

When you run a 4.2L f-150 without cats, is it expected for it to chug at low idles (when in drive or reverse)? I have had Cats removed because they were clogged, a while back and I replaced my EGR tube because the clogged cat blew it out and broke it. When the idles drop when under pressure, the oil pressure also drops. Now, please note, I have replaced oil filter, oil pump, oil pressure sending unit and even ran Seafoam with royal purple. Now, the oil pressure doesn't drop all the way to 0 any more, instead it just giggles when under pressure at low idles. I think the problem is that I have no back pressure. I still have my stock muffler so I don't see why it doesn't have enough back pressure but that is my only guess because it sounds like a drag car getting pulled off a trailor when its sitting at the drive-thru. It has gotten to the point to where it has died from very low idles, but it started right back up no problem.

Some codes I am getting is 4 for the O2 sensors, 2 for EGR and 1 for Mass Airflow Sensor. I understand the 02's and the egr but is the mas airflow related to the no cats, or do i need to replace my mass airflow sensor?

I already know I need to just buy cats for my truck so I thought about 2 high flows with a nice Flowmaster cat-back system. I still iffy about the MAF sensor though.

So my big question is: Will replacing my cats fix the problems with how my motor runs and the MAF or should i look into something else, and a new MAF sensor?

Is this worth it? Should I just let it sound like a drag truck, lol?

 

[MUDKICKR]

what maf code are you getting? there are several codes for that sensor alone and knowing what the code means will tell what needs done next.
also exhaust backpressure has nothing to do with low oil pressure, but now my question is what is your trk idling at? is it lower then usual? that can be why you have low oil pressure at idle and why it will quit sometimes.

 

[medwards29]

Well, I think when i took it to autozone the only repair option for the code was replace maf sensor, so it may be broke. My truck in neutral or park will idel at 800-1200 cold and 800-900 when warm when in reverse/drive it will idle normally 500-800, but I've seen it down to 300-500 and to kill. I understand what you mean about that, but I was thinking that since i have no back pressure I thought that would cause a lot of engine stress causing the oil pressure to giggle with the chugs. If it is still an oil pressure problem, then I have no idea what else to do to it. Is there anything else I could try? Note: I have Sea-foamed it with royal purple, put a K&N oil filter on it, changed lifters, Sea-foamed the fuel lines, replaced oil pump and oil pressure sending unit, and now i'm running Valvoline 5w-30 oil in it with another K&N oil filter. Do I need to change my oil type to 10w-30? That is the only thing I could think of, because I've seen some guys run true dual straight pipes on the 4.2L and it ran fine.

 

[93f250idi]

ive had many vehicles with no cats or mufflers so it shouldnt hurt anything other than maybe a valve.

 

[medwards29]

If it was a valve i think I would know, lol. The weird thing about all this is that it has never done this until i took the cats off, thats why i'm confident it is the exhaust. On the model I have wouldn't the low back-pressure and the o2 errors cause the computer to make the motor act weird? This truck has puzzled me since the day i bought it, lol. The weird thing about the whole thing is that if you keep it above 800 RPM's it runs like a beast, today I took it for a drag on some back-roads and It hauled pretty nicely, Nice little burnout and such,

 

[MUDKICKR]

Ill try to keep this brief, on a real computer it will show you different codes, unless the operator of the computer isnt trained to use it, with that said, the MAF sensor senses how much air is going into an engine. the 02 sensors sense how much air is coming out of the engine, without the cats you have less back pressure, which means the air flow is faster, so it thinks its running leaner, which the ecm then demands full rich to correct this. now if it was all stock and you had the MAF code, depending on what code you had would help tell us whats wrong with it.
if the MAF sensor is reading your engine getting x amount of air, but the o2 sensors say x amount of air + or - air is coming out, that is when the computer demands either a full rich or full lean condition, but, if you have a vacuum leak, air is coming in after the MAF sensor, unread by the computer, and coming out, which the o2 sensors read, and will say the engine is running lean.
ck for a vacuum leak first. then ck to see if your getting ground at the MAF sensor, if you have both then ck for your 5v referance with to see if your getting power.

 

[medwards29]

I know i have a code for lean fuel, i don't remember what MAF code i had exactly. I have checked for vacuum leaks once but, I am not very familiar with a vacuum line system, so I just pretty much made sure all lines to motor and such were connected.
So are you saying that there might be a vacuum line leak somewhere causing all this to happen? If so, where is the most likely place to check first?

 

[medwards29]

ok we went out and looked her over again and we actually found where it is most likely leaking from. There a split in the throttle body gasket. We also found some weather line by the heater box. So I'm gonna replace those and see what happens. Maybe get a nice little expensive throttle body spacer,

 

[MUDKICKR]

p0171 system 1 bank 1 running lean
p0174 system 1 bank 2 running lean
those with an MAF code, i would bet money there is a vacuum leak.
the small vacuum line that goes for your heater box, it runs your controls, if its leaking you should only have defrost.

 

[trapper]

Man i just had the same problem i know it sounds crazy but here was the problem with mine....I have the 4.6 V8 btw and was throwing the same codes.......... there is a Vac line that runs from the passenger side valve cover to the back of the intake..... behind the intake is a rubber elbow, when this gets hot it will crush and cause this problem what i done was use a dollar piece of heater hose and no probs anymore if it is this it is a ford only thing and will run you 25 bucks

 

[medwards29]

Thanks for your thoughts, The line i was talking about wasn't the one to the heater box itself but was just one close by, (besides I have all my heat and ac features). The throttle body gasket I know for a fact needs changed now, and I'm prolly gonna change out all the intakes gaskets because the idiot who put the lifters in never changed my gaskets, except for the bottom intake gasket itself. So Imma gonna change those and run a last good check through for leaks and run it and see what happens. Thanks once again.

 

[medwards29]

Ok so the crack I saw in the gasket wasn't a crack at all. I just realized while trying to pull off the throttle body that the shape of the gasket makes a void in between the gap but is still sealed in the inner part, so no leak there. I'm going to change my oil to 10w-30 for now on and see if it helps. So far this truck makes me
:***:

lol does that say it?

 

[Diesel_brad]

Let me get this straight. You think because you did something to the exhaust, this had lowered your oil pressure?

 

[MUDKICKR]

Let me get this straight. You think because you did something to the exhaust, this had lowered your oil pressure?

that was a well thought out, well planned, and very helpful post to this thread, why didnt i think of this before, this will definitely fix his trk.

 

[medwards29]

no doubt, i know the straight pipe is obviously putting my truck under stress, and I only figured since i'm running 5w-30 the stress is causing my oil pressure to drop, and i fixed everything that deals with oil pressure so, i am making some thoughts as to why it is doing it. Seeing that it only started doing this after we cleaned the cats out i pointed fingers at that as a possibility. You know, I'm not an expert at this stuff, so that is why I came to this site to get others thoughts and experience with the issue, not to have people make me feel like an idiot. If your not going to help then please stay off of my topics, but If you are going to give advice I would be more than happy to take it.