Help with 2002 4.6is rough running

[J.Belknap]

Originally Posted by bcredliner

Seems the best that swapping all ignition components side to side is move the issue to the other bank? Why not just disconnect current to one cylinder at a time and see if one or more cylinders change the rough idle the least?

I have disconnected, one by one, the coil plugs on bank 2 and with each one there was no noticeable change in running. I disconnected all 4 coils on bank 2 so it is only running on 4 cylinders and that is how it has been running all along. I put a spark plug in one of the coils and it does have spark. So it appears that the fuel injectors are not firing on any of the bank 2 cylinders.

Swapping all ingition from one bank to another will help clearly distinguish between an ignition and fueling issue on bank 2.

He may have an O2 sensor problem but the truck will not run like crap even if every O2 sensor has failed. It will just be in a less efficient open loop fueling map.

edit: Also, where are the misfire codes?

[murf]

I can take off all coils and switch sides. I would be happy if the problem follows the coils.

at the same time I will ohm out all the injectors.

[J.Belknap]

Originally Posted by murf

I can take off all coils and switch sides. I would be happy if the problem follows the coils.

at the same time I will ohm out all the injectors.

Coils and boots and plugs for the best initial test. That way there's no mixing and matching.

[murf]

I am putting in all new spark plugs.

[Rockit]

When you say you bought it not running it probably sat around a while not running.

Also make sure the throttle plate is clean and not sticking. When they sit for a while the carbon on the plate begin to stick causing the idle to lope.

Also verify the fuel is good. While your buying plugs buy some fuel injector cleaner...Chevron or Lobro-Molly and also add Star-Tron.

[bcredliner]

Disconnect one O2 pre cat sensor at a time and then do post cat sensors in the same manner.

Does the engine smooth out when you hold rpms at 2000-2500? Are new pre cat sensors OEM sensors?

[murf]

Originally Posted by Rockit

When you say you bought it not running it probably sat around a while not running.

Also make sure the throttle plate is clean and not sticking. When they sit for a while the carbon on the plate begin to stick causing the idle to lope.

Also verify the fuel is good. While your buying plugs buy some fuel injector cleaner...Chevron or Lobro-Molly and also add Star-Tron.

Shortly after I got the truck to run the fuel light came on so I drove it to the gas station and filled full with gas. I did not put any injector cleaner in there, yet. I have a full bottle of Techron that I will dump in there and will run the car for a bit so it gets to the injectors.

I swapped the throttle body with a running X5 4.4 so I think I am ok there but I will clean it anyway. I also have CRC MAF cleaner and will give that a blast as well.

[murf]

Originally Posted by bcredliner

Disconnect one O2 pre cat sensor at a time and then do post cat sensors in the same manner.

Does the engine smooth out when you hold rpms at 2000-2500? Are new pre cat sensors OEM sensors?

Yes, when you hold upper rpms it seems pretty smooth.

The o2 sensors are Bosch.

Can you give me a bit more detail on the procedure above? Car running, not running. At one point are they all disconnected? Should I just disconnect one at a time and see if things change and then plug it back in?

I have had o2 sensors on other cars mess with the computer and result in a poor running engine. These were Porsche 928's with only one o2 sensor. The fact the it appears the problem to only be on bank 2, it makes sense to check everything to do with just bank 2. Coils, plugs, injectors, and yes o2 sensors. Makes sense. I was getting a really high reading on the post cat bank 2 sensor which is why I replaced that one with a universal Denso unit. the reading was .80 or so when it should be reading closer to .45
The front o2 sensors are dancing around like you would expect.

I will try disconnecting them one at a time to see if something changes.

[upallnight]

Your best bet would be to get a program to monitor realtime data so you will know what you are up against. Disconnecting 02 sensors does not provide you with any type of data as to how the engine should run since the engine was designed to run with info from the 02 sensors. By disconnecting the 02 sensors you just introduce another problem as the DME will interpret the disconnected sensor as a fault.

I use an app called Torque to monitor realtime data. You can see from Torque if the 02 sensors are operating correctly. Voltage produced by the 02 sensors can be viewed, precat sensors voltage will varies all over the place whereas post cat 02 sensor voltage should be fairly consistent.

Do an internet search to find out what other owners have done to fix a similar problem or DTC.

Don't be fool into what a generic code will produce. I got a DTC P1093 which means the precat 02 sensors for bank 2 was too rich, change the bank2 02 sensor, but the DTC still came back, look at the internet and found an E46 owner with the P1093 code and he changed, MAF, Fuel filter, Fuel pump, all of the 02 sensors and he was still getting the P1093 code. Finally he changed the ICV and the code when away. I took out my ICV and sure enough the ICV didn't rattle when shaken so I order another ICV for the X. Installed it and I am happy to say that the P1093 code hasn't come back.

[upallnight]

Even though you believe the timing is correct for Bank 2, since you have spark and you can hear the injectors clicking I think your timing is off. I would perform a compression test on bank 2 to determine the health of the cylinders on Bank 2. Could be that the timing is off enough that you do not have good compression. From the voltage on the 02 sensor after the Cat for bank appears to be twice as much as bank 1. I would think there is too much oxygen in bank 2 so you do not have a complete combustion in bank 2.