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3.0 running bad

roadkill25

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My 02 3.0 is running bad, almost sounds like it's missing firing or not running on one cylinder and it back fires quite a bit. I've replaced the spark plugs wires fuel filter IAC and the downstream o2 sensor. The fuel pumps working fine and I'm at a loss. It's throwing a code but can't read it due to the previous owner deciding the normal plug in for the code reader was for loser and putting in a USB. I'm in the process of replacing the upper o2 sensor but one won't come out. Any help is welcome I'm just at a loss of what to do.
 
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fastpakr

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Can you explain the USB thing a bit further?
 

roadkill25

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There is a female usb up under the dash like they wanted to access it to change fuel air ratio and the truck doesn't talk to the reader
 

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Can you explain the USB thing a bit further?
I agree. Have a picture? Maybe he just plugged in some kind of adaptor that you can remove.
 

roadkill25

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I will in a bit across town right now
 

O No 3.0!

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A bad o2 sensor will not cause a misfire. You should start by checking that your coil pack is firing on all 6 cyls.
 

roadkill25

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I forgot about coil pack and I know was just listing things that i did recently. Also for those about the usb here's a picture.
 

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mc17eln

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I would do the following:

1. Do compression tests of all cylinders, which is independent of spark plug and fuel injector problems.

If one or more cylinders failed compression tests, you are looking at:

1a. (bad scenario) shopping a pair of heads ($500) plus expensive labor; or
1b. (very bad) a damaged piston or (worst) engine block plus very very expensive labor.

If compression tests are good, don't buy anything yet. Instead:

2. Restore the ODBII connector back to factory spec so you can use FORScan properly.
3. Buy the ELM327 FORScan hardware (about $25) and install FORScan (free) to a laptop.
4. Run FORScan and perform an OBDII Mode 6 test to find which cylinder misfire.
5. Swap spark plugs to see if misfire stays or moves with the plug.
6. Swap injector to see if misfire stays or moves with the injector.
 

85_Ranger4x4

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There is a female usb up under the dash like they wanted to access it to change fuel air ratio and the truck doesn't talk to the reader
Aftermarket radios can have a USB input in the back of the HU for a ipod or usb thumbdrive. My F-150 has one and my Ranger will when I get around to getting my new radio installed. As of right now it's USB input is on the front.

I suspect yours is something similar.
 

Burnsy

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Probably not your issue but check all plug wires make sure none are rubbing against a heat source that may have burnt thru one of the wires...inspect each one closely
 

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