Continued issues

Chris Baker

Chris Baker

Well-known member
Sep 12, 2019
81
1
Bolivar, Tn
I have an 04 Land Rover discover, 4.6. I am continuing getting miss fire codes such as P0300, P0303, P0305 P0306. Keep getting the code suggesting a Idle Air Control valve, which I have replaced. I am not getting codes, P1171 and P1174, which suggest the air fuel mixture is off. Can someone please help me figure out what is going one with this thing. I have worked on this Rover for over a year trying to get the bugs worked out of it and I am getting pissed.
 
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simondewing

Well-known member
Feb 10, 2020
59
11
Texas
Sounds very similar to an issue I had with mine which finally turned out to be a vacuum leak on the intake (valley) gasket.
Didn't find it until I had swapped out the entire engine as it was taking too much time to chase.
Obvious leak at the back (rubber seal hardened and cracked) once the engine was out

Simon
 
Chris Baker

Chris Baker

Well-known member
Sep 12, 2019
81
1
Bolivar, Tn
simondewing said:
Sounds very similar to an issue I had with mine which finally turned out to be a vacuum leak on the intake (valley) gasket.
Didn't find it until I had swapped out the entire engine as it was taking too much time to chase.
Obvious leak at the back (rubber seal hardened and cracked) once the engine was out

Simon
Click to expand...

Well I changed that when I put on the new ignition coils. I may have not torqued the bolts down tight enough.
 
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discostew

Well-known member
Sep 14, 2010
7,713
1,016
Northern Illinois
It might be a mass air flow meter for those fuel trim faults. Like was mentioned earlier about the misfires, it really kind of depends when it stores those faults. Theres a few different ways it could happen, and it's prettty relevant that it's the center cylinders.
1st is a misfire after you drive it till its fully at temp and then park the truck for about an hour. if it misfires when you retsart it hot I would suspect that you have coolant entering the cylinder from a crack in the block. It would shake a little or just run a little rough and smooth out then the light pops on.
2nd is it misfires under load, or hard acceloration. If it did that I would think plug wires or the very rare coilpack.
3rd is driving a long distance at highway speeds and the light comes on. You might not even feel it misfire if its under really light load. Then I would think the stuck valves. If I knew the trucks history and could be sure the heads are original to the truck I would think this wouldn't be likely. By '04 they kind of had the tight valve guide thing fixed. But if the engine was replaced or somehow you have an earlier model year cylinder head on the truck it could be possible.I guess.
 
Last edited:
Chris Baker

Chris Baker

Well-known member
Sep 12, 2019
81
1
Bolivar, Tn
discostew said:
It might be a mass air flow meter for those fuel trim faults. Like was mentioned earlier about the misfires, it really kind of depends when it stores those faults. Theres a few different ways it could happen, and it's prettty relevant that it's the center cylinders.
1st is a misfire after you drive it till its fully at temp and then park the truck for about an hour. if it misfires when you retsart it hot I would suspect that you have coolant entering the cylinder from a crack in the block. It would shake a little or just run a little rough and smooth out then the light pops on.
2nd is it misfires under load, or hard acceloration. If it did that I would think plug wires or the very rare coilpack.
3rd is driving a long distance at highway speeds and the light comes on. You might not even feel it misfire if its under really light load. Then I would think the stuck valves. If I knew the trucks history and could be sure the heads are original to the truck I would think this wouldn't be likely. By '04 they kind of had the tight valve guide thing fixed. But if the engine was replaced or somehow you have an earlier model year cylinder head on the truck it could be possible.I guess.
Click to expand...

I only feel or hear the misfires, at idle, in park or at a stop light in drive while holding the brake.. When we get on the road, it seems to run smoothly..
 
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Davsam28

Member
Aug 12, 2020
5
0
indiana
Did you get your misfire problem fixed? I am trying to chase down the 300, 303, 305, 308 codes as well. I do notice a mild misfire and my Crank sensor failed a few days ago. I have new Coil packs. New plugs and wires , changed it all after I did my head gaskets and replaced intake gaskets etc. mine is a 2001 4.0.
 
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Davsam28

Member
Aug 12, 2020
5
0
indiana
rovercanus said:
Check injector o-rings.
Click to expand...
Thank you, I also am suspect of the plugs and wires as well. I bypassed that Cali Hippie system a while back as well drilled out the ports and put bolts in there to plug the air inlets. Did the head gaskets and plugs and wires... the Parts store recommended their version of OEM. I am a bit skeptical.. I changed the injector o rings as they with the kit I bought. I will definitely be checking that closely. Is there any special diagnostic data to follow? I have a Autel Maxisys scanner but Rover software is fairly limited on the truck.
 
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Davsam28

Member
Aug 12, 2020
5
0
indiana
I ran some Royal Purple injector cleaner through and it has switched off my misfires and CEL for trip home from work , about 40 miles. , hopefully it stays that way
 
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