Hello everyone,

I am hoping someone out there has the answer to an ongoing issue, with my 2007 Ford Focus 1.8 Zetec.

Just before Christmas my engine started running on 3 cylinders. So I got home and and plugged in the code scanner, which showed a misfire on Cylinder 3 and a fault code. This pointed at coil pack, spark plugs, faulty injector, and a few other ignition related issues. I opted for the easy change first and changed the spark plugs first, which solved nothing then changed one of the coil packs also to no avail. Had a feeling that this was an issue that went a bit deeper , so put the car into a local garage for diagnostics. the results of this that I had a burnt out valve on cylinder 3. Given how good these engines are I found this very surprising. After getting some very high repair bills quoted just for labour, I found a place that could give me a confirmed price subject to what they found when the head was taken off. 

True to the diagnosis I had not one but 2 burnt out valves on the same cylinder. So these were change and the guy that done them I know and trust as I used to work with him in the motor trade. The cylinder head was put back on the block after the new valves were fitted, and this is where it starts getting mysterious.

When the garage started the engine it was very difficult to start and when it did fire up it ran like a bag of spanners. It didn't want to tick over, and on a road test had now power and the cloud of smoke that came out the back was enough to make the people behind think they were in thick fog. When you backed of the throttle the car sounded like it was about to explode. Some might say why was it out on a test drive if it sounded so rough in the first place, to which I have no answer an at the moment it is irrelevant. Once the car was back at the garage it was put on a scanner and it came up with a fault code  which indicated Throttle Position Sensor Switch D was the issue. As a check the garage cleared the fault and run the scan again and the same fault came up.

The whole throttle including switch d was changed as it is more or less a whole assembly, this made no difference to the running of the engine and starting. The garage checked the oil as a precaution and found that even though they had topped it up before the test drive it had burnt through quite a bit  of oil and smoked there garage out to the extent that you would have thought the pace was on fire. Various things have been changed to test different theories such as throttle bodies as the car is over fuelling. however even though the the oil was topped up to the max, it burns through this while sitting idle and has completely emptied the sump almost. The head casket is not leaking and the water expansion tank is no showing any signs of of emulsified oil, a compression test has been done and I would expect it to show about 175 all things considered, but on each cylinder it is going up to 250+ and bending the needle on the stop. I am having the ECU tested for faults, but was wondering if anyone has had a similar problem and was was the solution. Sorry for the long post, but trying to give as much information as I can to narrow comment down.

MAny thanks 

1 hour ago, Hong Kong Phooey said:

a compression test has been done and I would expect it to show about 175 all things considered, but on each cylinder it is going up to 250+ and bending the needle on the stop.

Has the correct head gasket been fitted ?  Has the timing been checked ?

Suggests that the gasket is much too thin for the compression to be so much higher. Maybe @TomsFocus will have a better idea of the problem.

19 minutes ago, unofix said:

Has the correct head gasket been fitted ?  Has the timing been checked ?

Suggests that the gasket is much too thin for the compression to be so much higher. Maybe @TomsFocus will have a better idea of the problem.

On this engine it is a timing chain, no belts, and the the gasket has been checked to make sure it is the correct one supplied.

Head Gaskets often come in a range of thicknesses depending on what tolerance the original Engine has been machined to and if the Cylinder Head has been skimmed then normally a thicker gasket needs to be used.

That doesn't explain all your symptoms though and you may have more than one fault.

I think the Fault Code could be a red herring and I would not change any component based on a fault code only, additional diagnostics needs to be done.

With faults like you have going back to basics can be the best course of action.  As @unofixsaid, the Valve Timing needs to be checked and some of your symptoms could be explained by one or more of the Valves not opening because of a problem with reassembly as well, maybe one of the Cam Followers has broken or not sitting where it should be.

I agree with @unofix and @Tizer. My first thought on reading the original post was that the engine has been incorrectly timed after reassembly.

Thanks for the comments guys, The timing has been rechecked, it was the first thing the garage went for and found i to be spot on. The head has not been skimmed and neither has the block, so on that basis the engine is standard. 

The compression test done (which I witnessed), may be high as the car is over fuelling, as the bore will be filling up with fuel, so with less space in the bore there would be an ever increase in compression with each turn of the engine.

I would agree that it is possible that there is more than one fault, which may have been exaggerated, with the removal of the cylinder head. Although as the car was running fine before the valve burnt out, I would be very unlucky to end up with more than one fault coming along just by the head being removed, however there is a first time for everything.

15 hours ago, Hong Kong Phooey said:

The garage checked the oil as a precaution and found that even though they had topped it up before the test drive it had burnt through quite a bit  of oil and smoked there garage out to the extent that you would have thought the pace was on fire

Re-reading the above reminds me that these Mazda-derived engines have a tendency to suffer piston ring faults. If it's burning oil to the extent you stated it should be obvious by examining the spark plugs.

On these naturally-aspirated engines the only way I know of oil getting into the combustion chamber is past the rings or down the valve guides.

1 hour ago, mjt said:

Re-reading the above reminds me that these Mazda-derived engines have a tendency to suffer piston ring faults. If it's burning oil to the extent you stated it should be obvious by examining the spark plugs.

On these naturally-aspirated engines the only way I know of oil getting into the combustion chamber is past the rings or down the valve guides.

Mike, I would agree with you, prior to the head being removed I had all the plugs out and other than cylinder 3, which had a burnt out valve, all the other plugs looked normal.  it is possible that something from the burnt out valve has dropped down, but this would damage the compression ring first and therefore the compression test would have shown low or no compression. I must add the garage has been great and checked and rechecked everything they can think of, and I have sat down with the owner and gone through all the possibilities, and we agree it could an over fuelling issue. But the oil burning just doesn't make sense. Other than there are other issues which have coincidentally appeared after the repair to the head.

When the valve(s) were replaced, were new valve guides fitted ? and are there valve stem oil seals fitted ?

2 hours ago, mjt said:

On these naturally-aspirated engines the only way I know of oil getting into the combustion chamber is past the rings or down the valve guides

Actually I've just realised there is another way - the crankcase ventilation system. Has the garage checked that?

1 hour ago, unofix said:

When the valve(s) were replaced, were new valve guides fitted ? and are there valve stem oil seals fitted ?

Yes new valves, guides and seals

48 minutes ago, mjt said:

Actually I've just realised there is another way - the crankcase ventilation system. Has the garage checked that?

They have fitted a new breather tube and valve, which I asked them to fit the day i took it in as the car was hunting a little and this seemed to be the issue to solve the hunting.

We've pretty much run out of suggestions now. Although you've said you suspect over-fuelling the fact that it's smoking badly and using a heck of a lot of oil suggests it's burning it. With everything we've suggested so far ticked off the list either the oil is getting into the combustion chamber(s) or is being blown out of the crankcase. If it was the latter there ought to be obvious signs of it and if the former you wouldn't expect such high compression readings** on all four cylinders.

There's also the question of why you had two burnt valves in the same cylinder and whether what caused that is pertinent to the current problem. Were they both exhaust, both inlet or one of each?

(Edits: one cause of burnt valves could be the clearances had closed up so that when hot they weren't closing properly.

** could the high compression be due to a partial hydraulic lock due to the quantity of oil in the combustion chambers? It just seems to be getting more absurd. )

3 hours ago, mjt said:

We've pretty much run out of suggestions now. Although you've said you suspect over-fuelling the fact that it's smoking badly and using a heck of a lot of oil suggests it's actually burning it. With everything we've suggested so far ticked off the list either the oil is getting into the combustion chamber(s) or is being blown out of the crankcase. If it was the latter there ought to be obvious signs of it and if the former it wouldn't be giving such high compression readings on all four cylinders. It's a total mystery.

There's also the question of why you had two burnt valves in the same cylinder and whether what caused that is pertinent to the current problem. Were they both exhaust, both inlet or one of each?

(Edit: one cause of burnt valves could be the clearances had closed up so that when hot they weren't closing properly.)

The fact that an exhaust valve burnt out is very unusual for these engines and the garage owner is very surprised. Yes it was 2 exhaust valves that burnt out. There is a theory that the crank breather valve may have caused the valves to burn out, and after reading some posts on the internet (not on the site) it could well be the cases.