My 2003 Disco idles very rough at least once for 5-10 seconds soon after starting, almost like it’s misfiring. It’s a very low groaning and struggling. It doesn't stall, in fact I don't even notice a change in RPM on the tachometer. Giving it gas revs and the issue worsens, but then after a short interval, it's normal again.

The SES light is NOT on but there’s a pending P0132 - Oxygen Sensor Circuit High Voltage (Bank 1 Sensor 1)

So far, it hasn’t had the problem while driving. This all started after several days of heavy rain but it was only sitting, not being driven. However, fuel economy has sucked for the last several months. I’m averaging 9mpg around town.

I’m wondering what to check first? Could it be simple like a fairly new O2 sensor failing or should I be looking at the coils or the MAS? So far, I popped all plug caps off and filled the connector with some dielectric grease.

Stats:
All 4 O2 sensors were replaced in June, 2013 - approximately 5K miles. They are Bosch.
Plugs are +4’s with Magnecore 8mm wires - only 10K on them.
Oil is Rotella T6 with M1-301 Filter.
I have the tick, and my mechanic thinks also a collapsing lifter (chug chug chug sound almost like an exhaust leak). Been driving just fine with all of this.
I have never done an induction cleaning - but I have run Seafoam or Lucas in the gas several times a year. I have had my share of SAI issues - a couple of new pumps and solenoids.

Many thanks for your thoughts.

 

Well if you are getting a 02 Sensor code it points to that. The issue is that you just replaced it. So before buying a new one, check the connection and lube it with some dielectric grease. Clear the code and see what happens.

The so called tick you have could be a big issue with a cylinder liner failing, which is a big issue.

But the rough idle at start up sounds like, a fuel system issue. ie. Bad tank of gas, poor fuel pressue, bad or dirty injector, bad injector seals..

I hope your vechicle isn't on borrowed time, but I was concerned about it I would have a fuel pressure test done to check the pump and filter. If it passes that you can try the seafoam, if that fails go through the injectors and replace the seals. But again, that would be my way of hacking through it.

 

So I'm a newbie and I def am not mechanically inclined but this happened to me last year I found a short in a interior light that continues to blow a fuse so had that repaired and magically fixed .. I'm assuming the early morning dew or increase in humidity penetrates the electrical system somewhere but this is not a mechanic talking lol sorry if it doesn't help. Wish I was as knowledgable as you all I'll get there. Best of luck please update us

 

I've tracked this down on two separate LR vehicles, a Freelander with KV6 and a 4.6 Discovery, both with Siemens ECU. In both cases, it turned out to be corrosion on the ECU socket pins which drive the coils. Dry weather, no problem, wet weather both missed and usually posted a misfire code. Note that neither ECU is exposed to the weather. Both fixed with cleaning the pins and using dielectric grease.

 

The motor should begin to behave normally as the weather clears, and the fault codes will no longer be present?? If this scenario repeats itself as the humidity and wet weather return then the problem should be moisture contamination within the portion of ECU directing power to coil packs??

 

I drove my truck last night to make an errand and the code didn't come back, nor the rough idle that I was experiencing on Friday. If it is all clear again tomorrow then I will chalk that one up to the moisture and weather change. I will clean up connections and do what I can to prevent this from happening again. Any tips and pointers?

 

I am having similar things with my dII also! Everything was perfect until today. I drove it without an issue to HEB but she threw all these codes and idled rough, didnt want to accelerate.
I am in SA, pretty similar weather to yours so I hope she will go back to normal after I leave the hood open under the sun to dry her up tomorrow.