Cold & Damp Starting Badly

I had the air filter housing out today (just to check the air filter) and the was a light film of oil inside the tube between where the breather hose joins and the throttle. The throttle was also quite dirty - not so much on the air filter side, but on the inlet manifold side. Or so I presume. When I sprayed carb cleaner it was running back out black.

I'd quite like to take the throttle body off, just to see quite how dirty it is. Is it really necessary to replace the sealing ring, as Haynes suggest?

As to the oil in the breather, is a small amount to be expected, or should they really be spotless? Worst case scenario would be worn pistons, but I did top the oil up to the max mark (perhaps a little over, if I'm honest). Could this cause excess oil in the breathers? There's no smoke out the exhaust and the dashboard oil monitor isn't complaining.

I'll clean the breather hoses thoroughly and check them in a week, to see if it's historic oil, or current.

I changed the coil pack today, but not the spark plugs as I didn't have right socket. The old coil pack was a Sagem type, the new a Bosch. Although I couldn't check the plugs themselves, two had clearly overheated (no. 4 nearest the timng belt and no. 2).

I'm assuming that the coils are paired cylinder 1 + 4 and 2 + 3, as I gather is normal? If so, having a problem on cylinders 4 + 2 would suggest the cause isn't likely to be a defective coil?

The cold start problem improved a lot after cleaning the throttle (or the weather got better!) but know it feels there might well be a misfire of some sort.

C3Safari wrote:I changed the coil pack today, but not the spark plugs as I didn't have right socket. The old coil pack was a Sagem type, the new a Bosch. Although I couldn't check the plugs themselves, two had clearly overheated (no. 4 nearest the timng belt and no. 2).

Hi C3Safari. If you have 2 bad plugs, you could well get a misfire.

I would be wary about fitting a new coil pack to bad plugs with the possibility of damaging the coil pack?

If you do manage to get the plugs out, remember which came from where and if you can upload their pictures that would be useful. The state of each plug can tell you a bit about the state of the engine.

I changed the plugs. NGK ones were fitted, my new ones are Bosch FR7DC+. Looking at them they seem very new. I was told when I got the car it had recently been serviced (which I took with a pinch of salt). If so they've done maybe 3,000 miles. In the pictures, the one on the left is nearest the battery, the one on the right nearest the timing belt. What I thought were signs of overheating are I think corona stains (oil vapours reacting with the strong current). Perhaps the HT extension seals on those two plugs were not as good. The head metal inside those two plugs was also stained, wereas in the other it was completely clean.

I had to take the throttle body off to reach the third plug, so I gave that a good clean. The inside was black with oil residues.

What I assume is a misfire is still there, when idling. Sounds like a very brief hesitation once or twice per second and is most audible as slight popping sound through the exhaust. There is also a tapping noise from the top of the engine (presumably the tappets), which increases with revs, until its too quick to hear.

I'm going to ask the garage to change the oil and measure in the correct amount. I might also ask them to check the valve clearances (which looks like a fairly simple job, but a bit beyond me).

Is it possible that the engine is running a bit lean?

C3Safari wrote:I changed the plugs. NGK ones were fitted, my new ones are Bosch FR7DC+. Looking at them they seem very new. I was told when I got the car it had recently been serviced (which I took with a pinch of salt). If so they've done maybe 3,000 miles.

They look almost new, so they were changed at the service.

When fitting new spark plugs, they should be 'gapped' to ensure the distance between the electrode and the earth is correct, which is 0.9mm for the C3. You need to use a tool to measure 0.9mm and this is usually a feeler gauge (amazon), but this purpose designed tool (amazon) is very useful.

I didn't look up FR7DC+, but its important to get the right ones, so I assume you picked the right ones for your engine.

C3Safari wrote:There is also a tapping noise from the top of the engine (presumably the tappets), which increases with revs, until its too quick to hear.

You may have something sticking or worn in the cam/camshaft area. Some of the petrol engines have hydraulic followers and some don't. The hydraulic followers can get sticky if oil changes are missed and other parts can wear and become damaged if oil changes are missed.

Changing the oil after the damage is done won't fix all of the problems.

Tapping from the top of the engine is a good sign of sticking or damaged cam/cam followers and valves.

You can inspect the cam shaft and followers with the cam cover off, but its more work to change the parts.

If the valves are not opening and closing at the right time, I would expect a misfire.

But misfire can also be caused by a badly firing injector.

C3Safari wrote:I'm going to ask the garage to change the oil and measure in the correct amount.

What does the oil look like on the dip stick? It may have already been done with the service.

C3Safari wrote:I might also ask them to check the valve clearances (which looks like a fairly simple job, but a bit beyond me).

Or you could ask them about the tapping noise from the top of the engine and listen to what they suggest on how to diagnose it.

C3Safari wrote:Is it possible that the engine is running a bit lean?

I would say not. The plugs look good and don't indicate lean. The fuel injection is controlled by the ECU and the first O2 sensor over a high sample rate. You would be getting O2 error codes on your OBD2 reader.

Well. The garage changed the oil and said that the oil was very thick (and probably very old) and wasn't reaching the head effectively. In any event, there's much less noise from the head now and starting up, the engine settles down very quickly. They also said the sump seal was rotten, so getting that done, cleaning out any sludge, flushing and refilling again should leave the car in quite good shape, as far as oil is concerned.

With hindsight, it's easy to imagine that starving the head of oil (even on an SOHC engine) would cause the car to struggle when cold.

Presumably if the problem gets worse again, I'm looking at either a blockage somewhere, oil pump issues or damage to the valve systems.

C3Safari wrote:Well. The garage changed the oil and said that the oil was very thick (and probably very old) and wasn't reaching the head effectively.

Thanks for the update.

I suppose it would be fair to say to any C3 owner that getting the oil changed at the correct intervals, with the correct oil can help avoid some problems later.

I still haven't got to the bottom of this cars problems, so I thought another update was in order.

To recap: the car started coughing and struggling keep running briefly when cold. I changed the plugs, coil pack and had the oil changed (twice, once with a new sump). The oil pressure was tested after, and was fine. This seemed to improve things, and certainly stopped the coughing on start up.

However, by then the car started to develop a 'put-put' popping sound from the exhaust, particularly noticeable at idle. There was also a metallic tapping sound from the cylinder head.

I took it to a garage, and they checked and adjusted the valve clearances. The cars performance at speed seem quite a bit better, but the tapping noise and popping exhaust was still there. I then took it another garage, with more experience of citroens, and they adjusted the clearances again. Apparently its quite common for the clearances to slip a bit after driving.

The second garage also looked for signs of wear to the cam/followers, but said they seemed ok (with the clause the you can only see so much in situ).

Whilst the car was just idling at the garage I commented that the popping sound was a little worse, and by the time I'd taken it for a good drive and got home the idle was very rough indeed. Driving seems fine, and the tapping from the head is a lot quieter.

I replaced the throttle body today, with little or no effect. The rough idle exists whether hot or cold, but the engine seems quite smooth if driving down hill, say, without the accelerator.

Any ideas? Does the throttle body need programming in somehow?

C3Safari wrote:Any ideas? Does the throttle body need programming in somehow?

No, the throttle body doesn't need programming.

C3Safari wrote:However, by then the car started to develop a 'put-put' popping sound from the exhaust, particularly noticeable at idle.

Poor mixture or poor mixture control. Are there any O2 sensor error codes stored?

No error codes visible on my cheap code reader, but it's booked in next week at the garage. The engine warning light has never come on, but does work.

One suggestion put to me was a possible fuel blockage /restriction. The engine seems to run fine above 1500 rpm, accelarates reasonably well on the flat (i.e. without much load), but struggles very badly on hills.

I replaced the MAP sensor because whilst idling badly, I disconnected the old sensor and it made no difference at all. Disconnecting the new sensor makes the car almost stall, but hasn't improved the rough idle.

Adjusting the valve clearances greatly exagerated the idle problem. Could be that they still aren't quite right, or that adjusting them somehow caused the ECU to start using faulty data from another part of the system.