03 5.3l Rough Idle & Exhaust Soot

[dmarek]

My 2003 1/2 ton 5.3L is idling rough and it leaves a black patch below the tailpipe in the snow after just a few minutes. Also the check engine light is on and it ocasionally flashes. It seems to run fine during acceleration and while driving. A friend suggested an O2 sensor so I bought one, the guy from the parts store said it takes the same sensor before and after the cat but usually the one after is the problem. I changed the one after the cat and the trouble was still there. I then called a different friend who is a Ford mechanic (lucky he answered my call cuz he is very busy ) he said the parts guy told me wrong, it should be the sensor before the cat. I went to his house and he put his code reader on it. He said the O2 on passenger side doesn't like right but he suspects intake air leak. We listened for sucking sound, thought we could hear a little but not sure from where. He sprayed carb cleaner all over but engine pitch did not change. SES light did flash but may be coincidence since it has been doing that some. I forgot to mention the soot to him as we were testing. Today I moved the new O2 sensor in front of the cat on the passenger side (it was allready very black after about 50 miles, not surprising considering the black snow patches in my driveway). No change in problem. I listened carefully with a hose to my ear for a suction leak, i'm not sure if I hear a leak. I think my mileage may have gone down but not certain. I bought an intake gasket kit and fuel line disc. tool but want to make sure I'm doning the right thing. Any input would be appreciated. Thank you.

[Norseman]

My 2003 1/2 ton 5.3L is idling rough and it leaves a black patch below the tailpipe in the snow after just a few minutes. Also the check engine light is on and it ocasionally flashes. It seems to run fine during acceleration and while driving. A friend suggested an O2 sensor so I bought one, the guy from the parts store said it takes the same sensor before and after the cat but usually the one after is the problem. I changed the one after the cat and the trouble was still there. I then called a different friend who is a Ford mechanic (lucky he answered my call cuz he is very busy ) he said the parts guy told me wrong, it should be the sensor before the cat. I went to his house and he put his code reader on it. He said the O2 on passenger side doesn't like right but he suspects intake air leak. We listened for sucking sound, thought we could hear a little but not sure from where. He sprayed carb cleaner all over but engine pitch did not change. SES light did flash but may be coincidence since it has been doing that some. I forgot to mention the soot to him as we were testing. Today I moved the new O2 sensor in front of the cat on the passenger side (it was allready very black after about 50 miles, not surprising considering the black snow patches in my driveway). No change in problem. I listened carefully with a hose to my ear for a suction leak, i'm not sure if I hear a leak. I think my mileage may have gone down but not certain. I bought an intake gasket kit and fuel line disc. tool but want to make sure I'm doning the right thing. Any input would be appreciated. Thank you.

 

What's the MIL code? That would be the best place to start.

[2000DV4.8]

I think I heard somewhere that a flashing check engine light means a misfire. I'd get the codes read before you do anything else. I'm pretty sure Auto Zone will do it for free.

[redvett]

A flashing SES light means do not drive. Serious damage to engine can result.

[dmarek]

I went to the parts store and had the codes read. It has a

P0300 random multiple cylinder misfire detected

P0131 O2 sensor ckt-low voltage bank 1 sensor 1

P1133 translates to H02S1 insuffiecient switches bank1 sensor 1

As I wrote earlier I purchased a new O2 sensor and installed it after the cat but have since moved it to the passenger side before the cat which I think is bank 1 sensor 1.

[rjirvine]

Bank 1 is drivers side, Bank 2 is passenger side. Sensor 1 is before the cat and Sensor 2 is after the cat. So, you're loooking at the drivers side sensor before the cat.

 

The random multiple misfire is disturbing. Have you dont anything to the engine since you got it (mods etc, or changed anything recently?). How long has it been since you changed the plugs? How many miles on the engine?

[dmarek]

I bought the truck 2 years with 25,000 miles it now has 55,000 miles. No mods have been done to the truck. Plugs are probably original as I have not changed them. I did switch from petroleum oil to synth (amsoil) about three months ago. I'm going to move the new O2 sensor to the drivers side and go get new plugs now.

[rjirvine]

It is my understanding the front sensors actually control the fuel trim, and the rears are there only to make sure the front ones are doing their jobs.

 

I would move the new O2 sensor to the drivers side forward of the cat and unplug the battery for about 30 minutes (so the computer will learn the new sensor). It may run a little like crap until the computer learns your engine again.

 

I'm concerned the carbon buildup is hurting your cats.

 

Things to think about:

- I would look at your EGR valve and make sure the gasket/passage/pintle is ok. (A new gasket is really cheap and easy if it looks bad).

 

- I would pull the plugs and see if there is any excessive carbon on any/all of them to help you troubleshoot.

[rjirvine]

The plugs are spendy. I switched to ngk tr-55 copper cores ($1.98 ea) gapped at .044 and haven't looked back. They work great. I would get an EGR gasket too, they are like $2.

[chevy6490]

I would stick with ac delco's, the vortec's tend to not like any other plug. I just picked up some ACD rapid fires and love them. There pricey though.

[rjirvine]

I replaced my stock plugs on my 2000 Silv with ac delco 41-985's since they didnt make my original plug anymore. My performance really suffered. I switched to the NGK's after reading posts on here and talking to Jesse at wait4me tune. I was leery of switching because I know what you're talking about with the vortec being finnicky. but the NGK's are working great!

[dmarek]

I disconnected neg term. on battery while I moved the new O2 sensor from passenger side before the cat to drivers side before the cat. It took about 30 minutes since I had to solder 8 connections. I thought about just leaving the new O2 in the passenger side and putting the one I removed from there into the drivers side since that O2 should be good but decided to just move the new one even though it was more work. I then reconnected the battery, trouble codes were still there. I then cleared the codes. started the truck, it seemed to run better. Check engine light is off. I let it idle for about 20 minutes and seems to be fixed. Small little circle patch of darkness in the snow (may be residual soot just clearing out)but nothing like what I was getting which was a black mark about 4" wide and a foot long. I've driven it about 10 miles let it idle some, SES is still out, running great.Thanks for your help.

[2005 Z71]

He sprayed carb cleaner all over but engine pitch did not change.

 

Oh the mad skills and secrets of Ford mechanics....

[Norseman]

I disconnected neg term. on battery while I moved the new O2 sensor from passenger side before the cat to drivers side before the cat. It took about 30 minutes since I had to solder 8 connections. I thought about just leaving the new O2 in the passenger side and putting the one I removed from there into the drivers side since that O2 should be good but decided to just move the new one even though it was more work. I then reconnected the battery, trouble codes were still there. I then cleared the codes. started the truck, it seemed to run better. Check engine light is off. I let it idle for about 20 minutes and seems to be fixed. Small little circle patch of darkness in the snow (may be residual soot just clearing out)but nothing like what I was getting which was a black mark about 4" wide and a foot long. I've driven it about 10 miles let it idle some, SES is still out, running great.Thanks for your help.

 

Still check the plugs.

[redvett]

There is no soldering required to change the O2's its just unplug and unscrew the sensor. You may have compromised the wiring and may have problems since the O2 works on millivolts.

 

 

I disconnected neg term. on battery while I moved the new O2 sensor from passenger side before the cat to drivers side before the cat. It took about 30 minutes since I had to solder 8 connections. I thought about just leaving the new O2 in the passenger side and putting the one I removed from there into the drivers side since that O2 should be good but decided to just move the new one even though it was more work. I then reconnected the battery, trouble codes were still there. I then cleared the codes. started the truck, it seemed to run better. Check engine light is off. I let it idle for about 20 minutes and seems to be fixed. Small little circle patch of darkness in the snow (may be residual soot just clearing out)but nothing like what I was getting which was a black mark about 4" wide and a foot long. I've driven it about 10 miles let it idle some, SES is still out, running great.Thanks for your help.