Intermittent heavy rattle, misfire and change in engine speed

[oilydigits]

Hello Everyone,

Usual thing - new to the forum and got a problem with a K11.

The engine lost power and misfired. when I looked at it, the two centre plugs had been left loose and the plug in number 2 cylinder had lost both the outer and inner electrodes. Number 3 plug had lost the outer electrode. The misfire was on number 2 cylinder and number 3 was still firing!

I put a magnet down the plug holes to see if I could retrieve any ferrous bits, but nothing came out. Did a compression check and Nos 2 and 3 were about 30 psi down on 1 and 4 (205 psi for 1 and 4). Replaced the plugs and the engine seemed to run fine, for about two days. Then the same thing happened and when I removed number 2 plug, the outer elctrode was closed, suggesting something had hit it. I replaced the plug and started the engine again and an intermittent mechanical noise could be heard, which sounded suspiciously like a piston hitting a valve, and it then disappeared. Drove the car home with no problems, but decided to remove the head to look for any damage and foreign matter.

Inspection of the head revealed some very light pock marks distributed all over, but there was no damage to the valves. One exhaust valve in nos 2 and 3 cylinders leaked during a petrol test, so I removed them and there was no damage, so lapped them in. I had the head skimmed (6 Thou) and replaced the head bolts and head gasket. The head was vacuum tested and found to be fine. Replaced the head, started up the engine and it ran perfectly. Shut it down to check the oil and coolant levels and replace some plastic guards etc (nothing on the engine) and started it again. Back to square one!

When ticking over, the rattle sounds very mechanical, but quite light - I would say something similar to gently tapping two light hammers together (which, of course, I would never do). Sometimes it is a sole rattle, others it can be a short burst of rapid rattles. In between these, and sometimes at the same time, there can be heard a very light 'tick' and the engine falters. After a while it goes on to three cylinders and dies.

This is a family member's car and she needs it for work, but I am at a loss as to what is causing this problem. Can anyone help me please?

 

[oilydigits]

More information:

The car is a 1.o litre, has not been modified or had the engine changed and has about 75,000 miles on the clock.

 

[Robodestro]

no chance part of the electrode could of made it past the piston and broke through some rings?

 

[frank]

have you tried a strobe on the timing oilydigits ? (assuming its pre 2000 ?)

 

[oilydigits]

Thanks for the suggestions guys.
Robodestro, that's certainly a possibility, but there don't appear to be any score marks down the bores.
Frank, it's a 52 plate - 2002 I guess - it also has coil packs.

I had been wondering if it could be caused by sticking valves. My reasoning was that if the valves had been slightly bent by the debris from the old plugs, one or more might stick as it rotates and that would produce the apparent randomness of the rattling. I reasoned that the impact causing the noise might be the cam hitting the valve (or shim) because of the excessive gap. There seemed to be no development of the noise to a catastrophic failure, so I thought the pistons hitting the valves would not be likely. So, to begin today, I thought I would check the compressions again before I removed the valve cover and tried to manually depress the valves. On removing plug no 3 I saw that the outer electrode had been pushed on to the central electrode, closing the gap completely. This, no doubt, reduced the engine to 3 cylinders. Now, I am assuming there can be only three possibilities for this:

1. There is some debris in the chamber that has been wedged between the piston and the spark plug. That was my initial assumption before I removed the head. The head was thoroughly cleaned before reassembly and there was no debris in the cylinder, so I am discounting that.

2. The spark plugs are too long and fouling the pistons. The problem with this is it has only happened on cylinders 2 and 3 and the rattling is intermittent. Also, I would expect the gap to be closed straight away and the engine to sound pretty sick more or less immediately. There have been two makes of plug used: NGK BKR5E and Bosch FR8DCX (as best as I can read from the plug). Both types of plug measure approximately 23 mm from the sealing washer to the outside of the outer electrode. The NGKs were sourced using the registration details and this showed the engine and chassis numbers on the shop database matched those on the car.

3. Somehow the pistons in cylinders 2 and 3 are occasionally travelling beyond their normal top dead centre limit and fouling the plugs when they do. I am totally at a loss as to how this could happen, but removed the sump today to see if there is anything amiss at the bottom end. I can't see anything unusual and applying pressure to the bottom of the con rod and underneath of the piston doesn't seem to produce any unusual movement or reveal any excessive play.

To go any deeper might involve just as much work and cost as obtaining another engine, but I would like to know what the cause is before I junk the engine.

The symptoms are exactly the sames as when I started on the car.

I really am open to suggestions and help.

 

[frank]

sounds to me like its detting somehow oilydigits, hence why i asked about the timing
were the pockmarks like this ?

mine has no idle control valve fitted, and the ecu uses timing advance to control the idle, which works fine but if i have the idle too low in the winter it the ecu applies loads of timing advance to stop the engine stalling (and the engine pinks like mad) so i run about 900 rpm in the winter, and 600 when its warmer
if i fit the consult cable i can see ecu moving the timing value up and down to keep a stable idle

 

[frank]

there are a few references to plug gaps closing from detonation if you google "detonation closed the plug gap" oilydigits and i,ve had it happen on mower engines when they have been tipped upside-down, and they smoke and clatter then cut out ( due to oil in the carb )
dodgy fuel maybe ? there was talk of petrol being watered down in eire the other week

 

[oilydigits]

I think you might have something there Frank. I have been doing some surfing on the net and detonation doesn't seem to be beyond the realms of possibility. I viewed some video on Youtube of a demonstration:



and this sounds very similar to what I am getting, except the rattles on my engine are not as regular.

There seem to be several possible causes of this, poor fuel being one of them. I checked with the owner and she filled the tank after I had replaced the plugs the first time. Assuming she didn't get the fuel from the same place (I'll confirm this tonight), she has had two different lots of fuel during the problem.

As you suggesteed earlier, advanced ignition timing can be the cause and this is where I would like some advice. I am going to put the engine back together and take it for a dagnostic test (I don't have the equipment / software / hardware), but before I do I want to check any obvious physical settings etc. My question is: where should the protruding pin on the idler wheel of the valve timing be in relation to sensor in the timing chain cover plate when no 1 piston is at top dead centre? At present, it is at the 12 o'clock position (rotating clockwise as viewed from right wing of the car) and has passed the sensor. Also, as only the central two cylinders seem to be involved, do they run hotter and could this contribute to the problem?

Sorry, but I rather foolishly bought the wrong Haynes manual (K12) and I am awaiting the correct one! Anyone interested in a brand new K12 manual?

Are there any other settings I can check before taking it for the diagnostic?

I am still keeping an open mind with regard to any mechanical impacts.

Thanks for your help.

 

[frank]

i would use an obd2 bluetooth reader personally mate, and view what the timing figures are when it starts to pink
there is a pdf manual link on here somewhere, and i think it would be the crank sensor or ecu at fault rather than that cam sensor
iirc the injectors run semi sequential in certain conditions, which may explain just the 2 cylinders being affected ?

 

[plmval]

Detonating at cylinders two and three may be due to low fuel pressure combined with weakest mixture via partially clogged filter baskets or tardy injectors operation. Interchanging injectors two and three with those at numbers one and four cylinders may eliminate or confirm this possibility?

 

[oilydigits]

Hi Guys,
Apologies for my absence, but I have been awaiting the results of running the car.

Frank, it looks as though you were right - thanks!

After dropping the sump and checkiong the bottom end and searching for any play in the conrods, I put it all back together and ran it. Initially the same racket and then suddenly cleared up! I took it for a diagnostic check and the garage found nothing - it ran perfectly while there and has done so ever since. Hoping that I have not put the kiss of death on it by writing this, all seems well and has been so for about the last week. So, unless anything else emerges, it looks as though dodgy fuel might have been the problem - it just took a while to clear. One to put down to experience!