Bought a 2004 Discovery 2 and already had 3 Amigos. Started up nice and drove good around town. Got on Highway and was okay until was driving up a hill and started to lose power. Put pedal to the floor to go up the incline and started having issues after that. Felt like throttle stuck and tack was around 4 to 5k. Removed foot from throttle but there was no response. Continued until I was on the decline and transmission finally downshifted and I regained throttle control. Truck started sputtering after that and CEL began flashing. Seemed to be consuming fuel very quickly after as well. It did have a "rich" smell like too much fuel and seemed like exhaust got louder after. Managed to get home okay and truck starts fine, just sputters still. Exhaust is pretty loud too. Hooked up code reader and had a bunch of codes come up. Misfires, Fuel Tank overfull, and Threshold over limit. Codes are as follows: P1590, P1300, P0327, P1170, P0304, P0306, P0302, P0300, P0303, P0430, & P0463. CEL went away after. Not even sure where to begin. I have read a lot of posts about similar issues. Wires, plugs, fuel pump, fuel relay. Stumbled across Catalytic converter failure that is causing exhaust restriction. So, is it wires and plugs causing the sputtering, or the fuel pump, or is it a blocked exhaust that is causing the engine to backfire. Looking for a bit of guidance on some things to try myself before dishing out all kinds of coin at the Garage. Any suggestions are much appreciated...

Cheers

 

If you don't know the maintenance history, check/change plugs and examine wires in detail. The dangerous stuck throttle indicates the throttle plate or linkages need cleaning/lube. Start with basic stuff first to try to clear misfire codes. Add code definitions to the code number to help us help you.

 

I don’t know how far you had to drive to get home after the CEL began flashing, but as you likely know a flashing CEL indicates catalyst damaging misfire.

• The key codes in your list are P1300, P0304, P0306, P0302, P0300 and P0303. Those are all misfire codes, as you likely know.
• The P0430 (Catalyst efficiency deteriorated - RH bank) may be being caused by the misfires, which result in more unburned fuel getting dumped into the cat.
• P1590 is related to the Three Amigos. Set that aside for now.
• I would also set aside P0327 (Knock sensor 1 circuit low input) for now, until you get the misfires addressed.

Misfires appearing simultaneously on multiple cylinders are not usually caused by problems with plugs or wires since those components fail individually.

These codes also do not point to failed ignition coils because none of these cylinders are paired with each other on a coil.

In my experience, multiple misfires on one cylinder bank can be caused by a faulty upstream O2 sensor on that side, even without typical O2 sensor codes.

The outlier among the misfire codes is P0303. Cylinder 3 is on Bank 1 and the other three are on Bank 2. Is there any chance P0303 is a typo and it’s actually P0308?

Regardless of that, I’d start with replacing the Bank 2 O2 sensor since three of the misfires are on that bank.

And, when it comes to O2 sensors, others on this forum have been recommending Walker over Bosch in recent years. Bosch sensors have been known by some to be bad out of the box (including at least twice for me). Here’s a link to the Walker sensor on Amazon.
Also, where are you located?

 

Hi. Thanks for the response. It seems you have confirmed one of my fears that I may have poisoned my catalytic converter? Do you think the sputtering will go away when the O2 sensor is replaced or is it sputtering because of the Cat? Did the timing slip when I floored the throttle causing the misfires? It seemed to be going along okay until I had the sticking throttle issue.

I am in Maine

Thanks again
RoverFun13

 

The timing chain did not slip.

It's not sputtering because of the cat.

The cat wasn't ruined in a short term, isolated incident.

The "sputtering" is the misfires. The engine is misfiring because the O2 sensor is telling the ECM to inject more fuel than needed and than gets burned.

Order and replace the O2 sensor and we'll go from there.

I hope you don't need to drive it before we get this sorted out.

 

Phew, that's a relief! Thanks. Ordered the O2 sensor (thanks for the link). It is due on Friday and I will try to tackle that this weekend.

 

Is Bank 2 on Passenger or Driver side? I only purchased 1 sensor but stumbled across a wicked informative video from British Atlantic and they mentioned a kit to purchase with 4. How likely is it I need to replace all 4? Perhaps the outlier code is telling me that both upstream sensors are bad? What are your thoughts? Thanks again...

 

Bank 2 is passenger side.

If you're ambitious and have the time, you could try swapping the upstream sensors from side to side to see if the misfires move to Bank 1. That would confirm whether or not the O2 sensor is the problem.

 

That many codes I would recommend lots of diagnosis before throwing money and parts at it.

a $10 elm327 and the free torque app you can read 02 voltages. They should start near one with a cold engine and begin cycling between .8 and .1 if teverything is normal. If they start near one and then go to .1 and stay there, you have good sensor but engine is running lean. If they do not start near one then you likely have bad sensors. The torque app can also monitor intake temp and maf airflow. Telltale that you have a problem with MAF is the temperature reading will not be 15 degrees over ambient.

I am a big proponent of swapping things left to right to confirm good or bad. Do them one at a time so you don't confound the experiment. Plugs are easiest, wires next, coils next, injectors last. You might be interestedin this is you get that far. https://extinctmotorsports.com/land-...elocation-kit/

You can disconnect the oxygen sensors and the engine will in to speed density mode, using only maf and rpm to determine fueling. Disconnect the maf and it will use only oxygen sensors for fueling. Do then both and it will use tps and rpm only.

 

Update => Swapped out the passenger side upstream O2 sensor as you had suggested. Fired her up and went from 12 codes down to 5! Sweet!

The codes I presently have are as follows:
P1590 => Same as previous
P1300 => Ditto
P0300 => Multiple misfires
P0306 => Cylinder 6 misfire
Knock Sensor 1 Circuit Low Bank 1 or Single Sensor

What am I looking at Next?? Thanks for all your help!
Regards,
RoverFun13