Technical No firing on no. 1 cylinder (cambelt end?)

[Mytheroo]

Hi, I'm not certain how bad my Stilo has been running generally, it's not been perfect but I'd not really thought I had a major issue.
Yesterday on a long journey it started getting lumpier and lumpier, especially low speed and idle. Nothing was showing on OBD2 (Torque app).
Eventually it felt like it was running on 3 cylinders, I limped home and slept on it.

So today I've been testing things a bit. Unplugging the coil-packs one by one showed #1 was doing nothing to help the engine (or maybe say 5% difference but too close to nothing to not dismiss the idea it was an illusion).
I was thinking (hoping) bad coil-pack, but replacing it didn't help matters. I also have a cheap laptop-based oscilloscope and amp clamp and this was showing pretty much the correct current waveform entering the coil-pack. I also tried swap testing the coil-packs from 2 and 1 cylinder and the issue remained with #1 .

I checked the spark plug (irridiums) and swapped 1 and 2 and the issue remained with #1 cylinder.

I ran the engine briefly (2 seconds?) with the spark plug out thinking if it was getting fuel I'd see some kind of mist exiting the plug hole, I didn't see any, but am not sure this is a valid test?

The plug wasn't bone dry each time I removed it, but it looked more like a dampness of slightly oily carbon rather than petrol. I couldn't smell any obvious petrol (though the plugs obviously smelled "engine-ey" ), and the plug was definitely not wet.

Using the amp clamp on each of the wires in the 5-way connector to the injector rail gave a waveform on each that suggested to me that the signal was being sent by the ecu...and as it is an amp tester I suppose this means the circuit is ok and that the coil in the injector is being powered....but I've only just thought of this as I am typing, and I've only just read about testing the other side of the 5-way plug. I'll go Ohm test it now but wanted to get this question asked as soon as possible.

Are there other tests I can do injector-wise?

Can they be fixed...even temporarily?

Is it common for them to fail closed as a mechanical failure while the electrics all seems fine?

Should I be seeing an engine code?

cheers, Tim

 

[varesecrazy]

Hi Tim.

Were the plugs of a similar colour?

Black..or bleached white could point to fuelling.

Are the coolant levels holding..?
Charlie

 

[Mytheroo]

the bad cylinder plug (#1 ) was darker than the #2 plug. which seemed the correct tan colour. #1 plug was definitely discoloured but I guess I expected something due to it not firing properly for at least 30 miles, and maybe slightly bad for months.
Coolant is fairly stable (months between top-ups if that) though there is an issue of a film of oil that appears in the expansion tank. This, however, was there when I got the car 18 months ago. I've drained and cleaned the tank once, but the film re-appeared over some weeks. I don't really know what to make of that, but there's no mayonnaise building up (there was a bit in the oil filter tube and cap but I wouldn't say it builds up much, I've wiped the cap maybe twice in 18 months as there was a bit of build-up)

 

[Mytheroo]

small update:

All four injectors measure 15.7 Ohms to 16.5 Ohms.

I suppose the injector could still be seized shut?

Is there a test other than remove the injector and watch it?

 

[varesecrazy]

I suppose the injector could still be seized shut?

Is there a test other than remove the injector and watch it?

Sooty dark plug points to fuel being present..but burning poorly.

Has the fuel economy been poor..??

 

[Mytheroo]

hard to say. Was getting 22mpg when I first got it, am getting 25mpg average now, 26/7 on trip B. This is urban dual-carriageway with chicanes every kilometre (Milton Keynes )

 

[Mytheroo]

would lack of fuel (less rather than none) cause a sooty plug do you think?

 

[varesecrazy]

Too much to burn cleanly..

Do check valve clearances

 

[Mytheroo]

update:

so at idle, removing the coil pack wiring makes little difference, but at higher revs it does make a difference.
I triggered each injector (in situ) with 12v and I can hear each clicking ok, obviously I haven't measured flow in any way.

I have a compression tester arriving tomorrow, and if that shows an issue I'll do a leakdown test to find the issue.

If you think it is fuelling too much, would running the engine with #1 spark plug removed not give me a fuel mist out of the spark plug hole?

 

[Ralf S.]

Take the injector out of #1 and stick it in #2 .

If the problem stays on #1 , it could be the coil or the plug breaking down at high rpm... .

If the problem moves to #2 , then it's the injector.

Forget the plugs and what colour they are.. there's a problem on the cylinder so whatever the cause, the plug colour will be irrelevant. A plug with no fuel to burn won't be the same colour as a plug that's burning *something* (however well or badly, rich or weak etc.).

If the problem stays with #1 , even with a different injector fitted then try a different coil (new or second-hand) to see if it fixes the problem (or changes the symptoms in some way). You do have a 1.6 though, so it could be an ECU fault... but eliminate the cheaper to fix issues first.

If the problem moves to #2 then it's the injector. Just change it.


Ralf D.

 

[Mytheroo]

thanks for that ralf, yes the injector swap-test is a step, though involves a lot more disassembly so have been leaving it till last.
The injectors measure ok on the ohm-meter, and all click with voltage applied.

Do you think a bad injector (mechanically) would cause less issue at higher revs (as my problem appears to act) or do you think idle should be better than higher revs?

I'll do compression test when Amazon arrives, and follow with leak-down if that test shows a problem.

 

[Mytheroo]

update: 50psi compression on cylinder #1 , 160psi or so on cylinder #2

Will do a leakdown test next to figure out the job

 

[Ralf S.]

thanks for that ralf, yes the injector swap-test is a step, though involves a lot more disassembly so have been leaving it till last.
The injectors measure ok on the ohm-meter, and all click with voltage applied.

Do you think a bad injector (mechanically) would cause less issue at higher revs (as my problem appears to act) or do you think idle should be better than higher revs?

I'll do compression test when Amazon arrives, and follow with leak-down if that test shows a problem.

I'd guess a bad injector would suffer more at higher RPM since it might be able to deliver enough fuel at lower RPM but not keep up with, or manage to supply a higher demand.

On the other hand.. looks like it's your no.1 cylinder, not the injector.

Have you put some oil in the cylinder to see whether the compression comes up? That would suggest rings, rather than anything more serious/expensive broken...


Ralf S.

 

[varesecrazy]

update: 50psi compression on cylinder #1 , 160psi or so on cylinder #2

Will do a leakdown test next to figure out the job

Test all 4 cylinders..with all plugs removed..

Then add a little oil down each plug hole..it should BRIEFLY improve the seal of worn rings.

But a blown gasket.or..nonsealing exhaust valve will still blow by.

At least you seem to have a clearer direction to search now..

 

[Mytheroo]

the leakdown test will do all this in one (AFAIK). Put cylinder at TDC and apply air pressure to the spark plug hole. Then listen at dipstick, inlet, exhaust and expansion tank for the escaping air.
Haven't done it yet though...

 

[Mytheroo]

update:

leakdown test was good on cylinders 2,3,4 (slight expected pressure through dipstick, past cylinder rings)

no. 1 cylinder was giving me air through cylinder 2 spark plug hole....so I immediately thought head gasket, followed by NOT head gasket as I'd have seen same from cylinder 2.

Put spark plugs back in 2,3,4 and air coming out of exhaust. Some though dipstick but I couldn't say if it was less, equal or more than with the other 3 cylinders.

So, I'm thinking broken exhaust valve, or valve spring, or something like that. I doubt that cam lobe would wear but it's possible.

With broken #1 exhaust valve, and #1 at TDC would you expect #2 exhaust valve to be open? I think #2 would be about to start exhaust stroke but not sure when the valve would start to open?

So next job is get the cam covers off.

Any advice on this? Only done the Seicento previously. I'm expecting it to be easy but not sure if any obvious pitfalls...

 

[Mytheroo]

well, "cam cover off" was a bit of a mistake, I kinda wasn't expecting the cams to be attached to the cover. The ECU end popped up a bit, but I got it all rebolted down and no harm done I think.

I also endoscoped the cylinder, and none of the valves looked broken or not closing. I think I'll have to try the leakdown test again (which told me an exhaust valve was not properly sealing). Something not adding up.

 

[Ralf S.]

update:

no. 1 cylinder was giving me air through cylinder 2 spark plug hole....so I immediately thought head gasket, followed by NOT head gasket as I'd have seen same from cylinder 2.

If pressurizing no.1 cylinder is causing gas to come out of no.2 then I'd say there is a head gasket fault, although I dunno how cylinder 2 manages to keep such a high compression ratio, if there is a knackered gasket between it and no.1. You'd assume the gas would equally escape from no.2 into no. 1... but only no.1 gives a low compression reading.

But... the most likely thing to go wrong is the most likely thing to go wrong .. so I'd rule out valve damage or anything requiring too many variables/planets to line up in the solar system. It'll be either a head gasket or a rings problem.

The only thing that is 100% for sure, is that you won't fix this without taking the head off. The cam cover should just lift off. I never heard of a motor where the cams are inside the cam cover.. (which engine do you have?).

Price up a new head gasket, cam-belt and tensioner kit (and a new water pump while you're at it) and then lift the head off. If you can't immediately see a knackered head gasket, I'll be very surprised. If on the other hand it looks fine, then at least you'll be able to examine the head, pistons and valves individually and "up close".


Ralf S.

 

[Mytheroo]

yeah the cams are in housings, and come off with the housing bolts. You can't look at the cam without removing them, and then only from the bottom after removing the hydraulic lifters from the housing.

Before this I took off the exhaust manifold and ran the leakdown test again. Got some leakage from 2 and 4, as well as massive leakage from 1, so have decided to have the head professionally renovated. Not sure the damage yet but the head guy said he could see valve burn on #1 exhaust. Head gasket looked ok, was a kind of 2 layer steel one. I thought after-market MLS but the new one in the gasket kit looks like it's the same.

Now I just have to learn about proper timing (I have cam locks but i'm not totally sure how the belt adjuster tool works, and the crank locking tool is also a bit weird. Just another learning exercise I guess.
I also want to check the hydraulic lifters as I was getting a small tick before the valve went doo-lally. Anyone know if they should be springy and compress? I have a new one but it doesn't seem to compress (maybe I'm not pressing hard enough though)

 

[Mytheroo]

small update:

Head is back from repairers. Only the one valve needed replacing.

The hydraulic lifters centre nubbins of the ones in the cam housings all lift if persuaded, and drop back down, making oil come out of the little hole. So I guess these are just pressured out with the oil pressure rather than also having a spring internally pushing them out. I couldn't get the new one to do this though, and its also slightly a different size (height of outer, plus width of nubbin) so I'm probably not going to use it. I'll just check the hole of each of the current ones.