Hi, truck all the sudden started running rough, idles rough, hesitation on acceleration, 2000 D2 SE7 with 130k, wife's daily/weekly driver.

I have codes 0171 0174 0300 0306 and need a little help. Some searching on the forums show the
0171 - bank 1 lean
0174 - bank 2 lean
Clean the MAF with MAF cleaner, I have done this last year and this code had come up once or twice this year but goes away pretty quickly.

0300 - engine missfire
0306 - misfire cylinder #6

I looked at Error Code List and obtained some info and also on the board and it appears to be related to 1)coil pack, 2) wires (replaced last year), 3) spark plug (replaced last year) or as stated on the above website "A code P0300 may mean that one or more of the following has happened: Faulty spark plugs or wires Faulty coil (pack) Faulty oxygen sensor(s) Faulty fuel injector(s) Burned exhaust valve Faulty catalytic converter(s) Stuck/blocked EGR valve / passages Faulty camshaft position sensor Defective computer".

I'm going to get an in line spark plug tester to see if the coil or wire is bad, but I'm wondering if all 4 codes are related.

1) Should I replace O2 sensors? (Don't know how old they are)
2) Would vacuum leaks be a likely cause? (Haven't seen much on the forum searches about this).
3.) How can I test 02 sensor?

Thoughts?

 

P0171 and P0174 means the engine is running lean. It runs lean for a few possible reasons.

Either:

The MAF is not functioning properly. In that case clean the MAF or replace it.

Or unmeasured air is entering the fuel system. What that means is some where their might be a vaccum leak. it could be a vacuum hose or a bad clamp or a bad seal on a fuel ejector or a bad gasket on the intake manafold system.

Or Your Fuel Pump is not creating enough pressure.

This video does a good job of explaining it:

 

Should not be your O2 sensor, these items are more than likely not related. I think if you focus on these things you should nail it down.

You might also want to read about the cigar test, or look up how to build a smoke tester for the vacuum leak.

 

Wow P0300 and P0306 means you plug on cylinder 6 is not firing all of the time.
Cylinder 6 in america is passenger side third from the radiator.

Reasons are Bad Plug, Bad Wire or Bad Coil Block.

Replace the plug, this is a 8 dollar fix and clear the codes, see what happens. it it works your good. To Note: you might as well change all of them. But one plug will work.

If the plug replacement doesn't work. Your pulling off the intake manifold and changing the wires, but if you go that far into it you might want to replace the coil blocks as well. good luck I hope it's the plug.

But it's is a good idea to use the inline test, you can get it at harbor frieght for 5 bucks
http://www.harborfreight.com/inline-...ker-69014.html

 

My Disco was suffering from all those same issues. First they said it might be the air flow meter, now they have decided that due to my mentioning some oil leakage its the intake manifold gasket as the previous reply mentions.