SSG_Holder

Ok, I appologize if this seems long but i have never asked a question on any online forum before. I have answered a few and I will try to be as detailed as I can be to reduce your frustration while trying to assist me. For the love of all things good in the world i hope someone here can help. Here goes.....

I have a 2002 Ford F150 with the 4.6L. It is a 2WD and automatic. I bought the vehicle with a bad transmission and changed it right at a year ago. A couple of weeks ago I started hearing a knocking sound coming from the front passenger side of the motor. Originally i believed it to be the tensioner pulley but upon further inspection I have ruled that out. The truck originally ran fine with the slight knock only happening when you first start the vehicle but that changed quickly. The truck now makes the knocking noise all of the time and drastically loosing power so i have stopped driving it. Here's the deal, my code reader stated that the vehicle is running too lean and had a missfire on 2 cylinders. I checked the coils to find that the 2 cylinders that were missfiring had bad coils. I always have basic needed parts for my vehicles laying around as i tend to buy them before i need them. With that said i went ahead and changed the plugs and coils on all 8 cylinders. I checked the fuel pressure and injectors which all came back as good except for one injector which i replaced. The vehicle continued to knocked a bit but was running great. Now all of a sudden the knock has gotten louder. With the vehiclw in park it idles fine and has power if you rev the engine but once the motor gets warm if you put the vehicle in drive the RPMs will rev as you give it gas but the vehicle will not increase speed. Max spwed is around 35 MPH. It does not act as if the transmission is slipping. It almost acts as if the transmission iant being told to shift, but that wouldnt explain the knock. The vehicle also acts as if it has a hard missfire when you try to accelerate. I hooked the scanner up to it and again it is telling me that the vehicle is running lean and the same cylinders as before are missfiring.

I am thinking the problem may be with the timing chain and/or tensioners as the sound does come feom that general location and greatly resembles the sound of a chain thunking around and hitting the cover. Before i start tearing this thing apart i was hoping maybe someone here could tell me if they have had the same problem and if this was the cause. I greatly appreciate any and all guidance.

RLXXI

1st thing you need to do is a compression test. Remove all spark plugs, disable the fuel and/or ignition system, install the gauge in each cylinder and hold the gas pedal to the floor, spin the engine for 10 secs on each cylinder.

Report back with your findings for more information.
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djfllmn

iTrader: (1)

I agree with this but also suggest an exhaust backpressure test

SSG_Holder

Ok, so i did as you said.i disconnected the electrical plugs to all of my injectors and used my compression gauge to check the compression. I have compression in all 8 cylinders reading between 150 and 160 which sounds good to me but ive not worked on many fords so im not sure what its supposed to be. Also i put the plugs back in and started the truck in order to pull it in to my garage as it has started to rain here. Still idles perfectly but when put into gear i can put the pedal to the floor and the vehicles RPMs will slowly increase but the vehicle will not move.

I will get to the exhaust shortly.

RLXXI

That's good compression readings. Easiest way to test for plugged exhaust is to drop the pipe(s) loose from the exhaust manifolds. It'll be loud as hell but if it's plugged you'll see a noticeable increase in rpm climb when accelerating.
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SSG_Holder

Ill have to wait for this rain to pass but ill let you know what happens with the exhaust. Thanks for your help

SSG_Holder

Alright, i dropped the exauhst off and there is no change. Any ideas on what i should try next?