Constant Misfire and O2 Codes

Chris Baker

Member
Sep 12, 2019
24
0
Bolivar, Tn
I have an 04 Disco II with 4.6. I have replaced plugs, wires and coils. I keep getting codes of random misfires on #3,5 and 6. also the code of both first bank O2 sensors keep coming up as well. You can feel the misfires at idle. But when traveling down the road is feels pretty smooth.
When we first start it in the morning, it will idle pretty high around 2500 RPMs or it will rev up and then try to stall out. This is only during a cold start. After about 30 sec to a min, it will straighten out.

Does anyone have any idea what I can check to get her running and idling smoother where these codes don't come on. Also is the O2 codes being thrown due to the misfires?
 

rovercanus

Well-known member
Callsign: kj4csi
Apr 24, 2004
9,246
43
No, the O2 codes are being thrown because you have an O2 sensor issue.
Bad sensors will definitely cause the problem you are having. I would change out the front O2 sensors. Don't cheap out, the ebay shit doesn't work.
 

Chris Baker

Member
Sep 12, 2019
24
0
Bolivar, Tn
No, the O2 codes are being thrown because you have an O2 sensor issue.
Bad sensors will definitely cause the problem you are having. I would change out the front O2 sensors. Don't cheap out, the ebay shit doesn't work.
So cheap and/or bad O2 sensors will cause the issues with the way its running and possible misfires?
 

JUKE179r

Well-known member
Sep 14, 2016
394
26
Suffolk, UK
List what codes you are getting. Can your diagnostic tester to check the voltage of your O2's? If you have SAI then you have 4 O2 sensors to figure out.
If you have to get O2 sensors... get NTK #25623 UP & #25624 DOWN or Walker #350-34462 UP & #350-34188 DOWN. Denso maybe but ***NOT Bosch!***
 

Swedjen2

Well-known member
Sep 12, 2018
260
37
California
List what codes you are getting. Can your diagnostic tester to check the voltage of your O2's? If you have SAI then you have 4 O2 sensors to figure out.
If you have to get O2 sensors... get NTK #25623 UP & #25624 DOWN or Walker #350-34462 UP & #350-34188 DOWN. Denso maybe but ***NOT Bosch!***
Not Bosch?!?!? WTH? O.K., need an explanation....other than, "they suck".
 

squirt

Well-known member
Nov 13, 2008
812
11
Los Angeles
Like everyone else said - What O2 codes are you getting?

What are the real-time numbers from the front O2 sensors when the vehicle is warmed up? What do the long term fuel trims look like?

O2 sensors have absolutely nothing to do with cold start behavior, so that will be a separate issue. (Vacuum leak or IAC motor is a good place to start looking)
 

Chris Baker

Member
Sep 12, 2019
24
0
Bolivar, Tn
List what codes you are getting. Can your diagnostic tester to check the voltage of your O2's? If you have SAI then you have 4 O2 sensors to figure out.
If you have to get O2 sensors... get NTK #25623 UP & #25624 DOWN or Walker #350-34462 UP & #350-34188 DOWN. Denso maybe but ***NOT Bosch!***
The codes I am getting are P0305, P0306, p0307, p0303, p0150, p0130, p0300, p1300,
 

rovercanus

Well-known member
Callsign: kj4csi
Apr 24, 2004
9,246
43
Looks like your bank 1 oxygen sensor is bad. I would replace both fronts with OE Bosch. Give Will Tillery a call.
I had a similar issue a couple of years ago except I didn't have the O2 fault, just mis-fires on one bank.
Another thing possible that Will mentioned when i talked to him about this is the MAF sensor.
 

JUKE179r

Well-known member
Sep 14, 2016
394
26
Suffolk, UK
Ok... in descending order direct from the RAVE workshop manual...
p0130 - Front sensor LH bank stoichiometric ratio outside operating band
p0150 - Front sensor RH bank stoichiometric ratio outside operating band
p0300 - Excess emissions level of misfire on more than one cylinder
p0303 - Excess emissions level of misfire detected on cylinder No. 3
P0305 - Excess emissions level of misfire detected on cylinder No.5
P0306 - Excess emissions level of misfire detected on cylinder No.6
p0307 - Excess emissions level of misfire detected on cylinder No.7
P1300 - Catalyst damaging level of misfire on more than one cylinder

Have you cleared the codes to see what happens?

For high idles, clean out your IAC valve with throttle body cleaner and an old tooth brush. while you are there, clean out throttle body/plate too.

As far as Bosch brand of O2 sensors, I've never used them since i religiously use NTK sensors on my cars. I've only read from other Disco forum members how random the Bosch sensors work. Basically, users state it's a 50/50 chance of getting a good sensor.
I do prefer Bosch for everything else electrical on my V8 except O2 sensors. Just sayin...
 
Last edited:

rovercanus

Well-known member
Callsign: kj4csi
Apr 24, 2004
9,246
43
Didn't see the p0150 in the mix. That kind of points to the MAF. Cleaning it is a hit or miss proposition.
With 18 years of D2 ownership, I've never had an issue with Bosch O2 sensors.
 

Chris Baker

Member
Sep 12, 2019
24
0
Bolivar, Tn
Ok... in descending order direct from the RAVE workshop manual...
p0130 - Front sensor LH bank stoichiometric ratio outside operating band
p0150 - Front sensor RH bank stoichiometric ratio outside operating band
p0300 - Excess emissions level of misfire on more than one cylinder
p0303 - Excess emissions level of misfire detected on cylinder No. 3
P0305 - Excess emissions level of misfire detected on cylinder No.5
P0306 - Excess emissions level of misfire detected on cylinder No.6
p0307 - Excess emissions level of misfire detected on cylinder No.7
P1300 - Catalyst damaging level of misfire on more than one cylinder

Have you cleared the codes to see what happens?

For high idles, clean out your IAC valve with throttle body cleaner and an old tooth brush. while you are there, clean out throttle body/plate too.

As far as Bosch brand of O2 sensors, I've never used them since i religiously use NTK sensors on my cars. I've only read from other Disco forum members how random the Bosch sensors work. Basically, users state it's a 50/50 chance of getting a good sensor.
I do prefer Bosch for everything else electrical on my V8 except O2 sensors. Just sayin...
Ok, I will try your suggestions. I have not recently cleared the codes but when I did it ran about the same. The engine light stayed off for about 2 days then it eventually came back on. I have recently cleaned the Throttle body. But I wondered if I need to get a new Throttle position sensor for it.
 

rovercanus

Well-known member
Callsign: kj4csi
Apr 24, 2004
9,246
43
Ok, I will try your suggestions. I have not recently cleared the codes but when I did it ran about the same. The engine light stayed off for about 2 days then it eventually came back on. I have recently cleaned the Throttle body. But I wondered if I need to get a new Throttle position sensor for it.
Throttle position sensor has nothing to do with these codes.
Will your scanner read actual data? Can you see what your MAF and O2 sensors are reading?