KV6 engine P0172 Code and misfiring/lack of power
 

Hello All.

I have a freelander which has the KV6 engine so hoping someone on this forum may be able to help me. The engine warning light has come on and keeps coming on even after clearing the DTC.

The code is P0172 which is Bank 1 Engine Bank too rich.

The o2 sensors have been replaced and they were not working, but the engine code came back.

The engine is very lumpy when it is idling and almost feels as if there is no power low down until you rev the engine and then it kicks into life.

Its been in the garage today and there was also a misfire code showing on their diagnostic equipment. Spark plugs have been replaced and the coils tested and all fine. But still no power low down and misfiring. Headgasket etc was all tested and I've been told was fine.

The fuel trims codes are also showing the engine is running very rich, down about -20% on Bank 1 which is what is setting the P0172 code off.

The inlet manifold (plastic thing on top) doesn't appear to make any noise when you shake it and taking the balance vis motor off showed the butterfly valve was ok.

Currently running out of ideas and thinking the engine has had it with a ghostly problem.

Has anyone else had a similar problem? Or can think of something else we can try?

How long did it take before the 'check engine' light illuminated again?

Simon

Anything from 10 miles to 100 miles. Went a whole week without coming on. Always comes in at idle too.

You might have a dying catalytic converter. I've got a similar problem with my Citroën C3 and I haven't been able to find what's causing it.

Simon

wouldnt a dying cat be caused by rich engine and misfire rather than the cause?

Based on what you have said i would get the bank 1 injectors tested for leakage.

Does your engine have spark plug leads? They can degrade over time.

Spark plug leads are all fine, coils are working.

It seems everything is working as it should be, but the engine is running really rich. The mechanic thinks it could be the inlet manifold and air is escaping through it somewhere making the engine think it is running rich.

Both of us are baffled about what it could be. Even had an endoscope in around the inlet maniforld to check the valves etc.

Would VIS motor failure cause the engine to run rich and misfire?

No.

In any case, this is something specific to the LH bank and the VIS system affects both banks.

Simon

I'm thinking the total lack of power until 3000rpm could be the vis motors. (read back over my OP) I missed this bit out. The car is kinda like driving something with an on off switch rather than a nice smooth throttle.

That's usually the symptom of the balance flap stuck in mid=position because the actuator has stopped working but (1) you said that the balance flap was o.k. and (2) you haven't got a fault code for the VIS system.

Are you going to try Phil-T4's suggestion?

Simon

Hi simon. Yes sorry we have tried Phil-T4 suggestion and injectors all appear sound and pulsing fine.

I checked the butterfly valve and it moved etc. But not checked the actual motor. So waiting for new VIS motor to arrive. Slowly ruling things out.

So it appears after a compression test one of the cylinders is half what it should be which is what is causing the misfire. Possible a leaky/burnt/bent valve. Looks like I'll be dismantling this engine to try and fix it :duh:

A sticking hydraulic tappet would cause that too. Or if the oilway to the tappet is blocked the tappet(s) will slowly lose oil and this will cause lack of compression.

A couple of months ago I had a KV6 that wouldn't start, history was that the car had been stood for about 3 months. The owner had tried everything. When I looked at the car and tried to start it it turned over as if all the plugs had been removed. There was no compression at all.

After numerous attempts to start the engine it would give an occasional slight hiccup. It had a full charge in the battery so I thought I'd do something I don't like doing I turned it over on the key continuously for a good 40-50 seconds :eek:
The engine spluttered and then roared into life, result :D
What had happened was that while the car was stood the tappets had lost their oil, turning over the engine sufficiently built up the oil pressure which refilled the tappets enabling the car to start.

Not saying this is the cause but it can be a possibility ;)

Russ

Interesting you should say that as the car was stood still for quite a while. However we've done about 200 miles since it was stood still so I would have thought it would have had time to clear?

I am having a slightly similar problem. Occasionally when I start the engine from cold the engine fault light comes on. Misfire on cylinder 2 is detected. If I clear the fault with my Autel gadget the fault clears and everything is perfect until the next cold start. Although sometimes I can have several cold starts without the light coming on. I have changed the plug and the coil on that cylinder. Yesterday I replaced the injector. The new injector looks differrent from the one I took out see photos. I was sure I had found the culprit but no, this morning the cylinder 2 misfire fault came back. I am hoping that the plug may be fouled (if the injector was faulty) and it will either clear itself or a new plug will do the trick.

Fred

cylinder 2 misfire has come back. Looks like a major overhaul when the spring weather comes!