V6 F-150 no cats

medwards29 · Jan 9, 2011

I'm almost positive there is a vacuum leak somewhere, but I talked to a fellow college and he told me that if the o2 sensors don't read right then it will retard my timing and cause it to run at lower idles and I assume with the combination of the exhaust leak at the manifold (from the broken stud) and a small vacuum leak, it is running the way it is. Again the low oil pressure only happens when it gets under 800 RPMS. The solution he gave me was a chip, programmer or 02 simulators. Now I'm probably going to get a chip, and have my uncle give it a vacuum test and then get the exhaust leak fixed.

MUDKICKR · Jan 9, 2011

o2 sensors in no way affect timing. all they do is tell the computer if the engine is running lean or rich and then the computer will richen up or lean out the fuel mixture. a vacuum leak will not let it idle correctly, and it will throw up lean codes. how many months have you been talking about fixing this and nothing has happened? first things first, FIND YOUR VACUUM LEAK AND FIX IT, then go else where. if you want a quick test to see if it will quit with a vacuum leak, unplug the vacuum line from your brk booster.

Diesel_brad · Jan 9, 2011

A chip is a complete waste of money

MUDKICKR · Jan 9, 2011

Diesel_brad said:
A chip is a complete waste of money

x2. well x10000000000000

medwards29 · Jan 11, 2011

ok well i have tried looking for a leak but have found nothing, i have even checked the notorious splitting elbow connectors for the 4.2L but they all seem fine. And 91idi removed the intake hose from the intake and it quit running immediately, so does that say anything? I'm not an expert with vacuum systems and i haven't been able to get a hold of my uncle to look at it. sorry, im just trying to get more information from u guys to see if there is anything i can do while i wait for him to become available.

Recently I've noticed while its running at low idles the truck will shake really bad and even when i take off it will shake up until 2000 rpm and will knock a little, but ive already replaced my lifters and had motor looked over so could this be a stuck injector??? again idk just getting information. I wanna make a list of things i need to do when i take it to my uncle. I'm going to have him run a vacuum test, but i know what i am experiencing has to be more than just vacuum problems. I also have 3" exhaust from the manifolds back with no cats just an fyi.

medwards29 · Mar 10, 2011

I have finally solved the problem. Yes there was a small vacuum leak, the elbow under the plenum was split, but fixing it didnt change too much. Found out cylinder 2, 5, and 6 were all misfiring. 2 was completely dead, and 5, and 6 were still firing but were very weak, with low compression. Changing coil pack fixed cylinder 2, but cylinder 5, and 6 still weak. Mechanic said that I had a blown head gasket and wanted $1000, and I said NO!!!! lol So I got a summer build project now for my top end

91idi · Mar 11, 2011

Guess you want help. LOL

medwards29 · Mar 12, 2011

hell ya i do! lol, even though I didn't help too much with ur 6.9L, but stand around and look pretty, lol, oh yeah and lift that huge head with you that seemed to weigh a ton!

MUDKICKR · Mar 12, 2011

what was the compression readings? was the compression tested hot or cold? whats the compression readings across all cylinders? how about a cylinder leakdown test? did he have all the spark plugs out when he did the compression test? how long did he crank the engine for the compression test? did he do a block test? did he blow air into the cylinder to see where the air came out? the 4.2 usually doesnt blow head gaskets too often which is why i ask.

medwards29 · Mar 14, 2011

I don't know I wasn't the mechanic.

medwards29 · Jul 15, 2011

update time.

Cracked head and head gasket was split between cylinders 5 and 6. Lower intake manifold gasket was falling apart and the cyl 6 spark plug wasn't even threaded in all the way from the last time I took it in to get looked at.

Results: Brand New Top end. Idles at 700-800 RPMS in gear, sounds good, sounds quiet, the Cold air intake actually makes a sucking/whistling sound now, and all new plugs and deep clean to the motor. Bottom end looks very good, but, low oil pressure light still trips and gauge still jiggles. I have noticed that it does it when it want's to. Sometimes it will do it under the same stress as when it isn't doing it, so I think the gauge is just a piece. My compression was excellent and no noises or ticks so I'm gonna get it oil pressure tested to make sure it is just the gauge, then gauge pod!

here is a pic of the progress so far:

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http://s1179.photobucket.com/albums/x392/medwards29/?action=view&current=Video07091953.mp4

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oooooo, and i built this little gismo in the meantime:

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medwards29 · Jan 19, 2012

So far so good. New ideas and plans for future mod. But first my current mods:

Cold Air Intake: