Engine running on 3 cilinders once every few weeks

[Rob]

Ok, I’ve had a hard time comming up with a title for this one.

Lets start with some infos, the car is a 97 Mitsubishi Colt (goes as Lancer 3d or Mirage in various parts of the world also) with a 1.3 (multipoint) injection 4 cil. Manual transmission and 170 000 miles on the counter.

She starts fine, always at the first instant you turn the key. But once in a while, say ever 2 weeks orso, it’s idling a tiny bit rough, (I notice a vibration at this point, a passenger probably wouldn’t notice a thing) but when you touch the gas, it runs on 3 cilinders ‘completely’. The acceleration is reduced and you can feel a pulsating hessitation. This lasts for about 45 seconds, and then everything is fine again for another two weeks. Applying more power seems to make it retrun to normal quicker.

This has been the case for I’d say 4 months now… and I can hardly call it problematic.. but it ain’t right either. Even if i’m goiong to live with it, I want to know what causes it.

One thing i’m suspicious of is and oil leak from the valve cover down in to the sparkplug well (tiny leak).. but I’ve kept that clean and still it occured. So perhaps I should be looking elsewhere too?

Thanks,

Topic

[college man]

No cel or codes? cel not flashing when power is reduced?

[george gonzalez]

if it happens right at startup, it could be from oil dripping down the valve guides and fouling the spark plug, or yipes, even a head-gasket leak where coolant is seeping in. Although you usually see blue or white smoke from the exhaust in those cases.

[Rob]

No CEL or anything no, its had its yearly check a month ago, no idea if they hooked it up to a scanner. I don’t think they had any reason to. When I asked about additional things i should know, aside from the test, only a rust patch came up. No (blue) smoke either, not normally and not when its hessitating.

Edit: the oil consumtion/loss is fairly undramatic, and rather constant for the past 2 years. If i’d had to put a figure on it, i’d say less then 1 liter per 6000 km. Hard to say as I add a little every other week pretty much. (1000+ km per week isn’t uncommon for me, to put that in perspective)

[Lorrin Barth]

This is just a flyer but some Mitsubishi cars would go into limp mode and shut off fuel to a cylinder the computer thought was misfiring. This should however give a CEL. Could you have missed it?

[Glenn]

Rob36, have you confirmed the car is running on three cylinders when this happens? I just wonder how you concluded that’s happening. Could it be something else, like perhaps a coil or secondary ignition misfire? It does seem strange that it’s at start up though. With no CEL codes, this may take some time to track down. Here’s an idea in the event it’s fuel related. Check the injectors with a mechanic’s stethoscope. If you can catch it acting up at home, shut the engine off and pull the spark plugs. Visually examine them to see if any of the 4 are wet, or fouled compared to the others. This may get you zeroed in on a particular cylinder, and if so, you can do some troubleshooting from there. Of course, getting a good scan tool on that vehicle would let you see live data for a number of possible contributing components. Good luck with this. Let us know what you find.

[college man]

see if this helps.

http://www.ericthecarguy.com/faq/solving-automotive-performance-issues

[Rob]

Thanks for the replies all,

I’m going to see if I can get my hands on a scan tool or have someone do a read out on it. I didn’t consider the possibility it might cut one cilinder on purpose for another reason. Although I am sure the CEL works and that I haven’t failed to notice it. It burns for 2-3 seconds when starting, always, then it goes off.

What caused me to say its running on 3 cilinders, well basicly I forgot to install one of the leads after cleaning the oil off it one day, and that produces exactly the same symptoms. To be fair i’m not sure if its always the same cilinder, and if it misses 100% of the time. At idle its hard to notice anything off, raise the rpm and it becomes very apparent.

The suggestion of checking the plugs when it occurs is a good point, I’ve put the tools in the car, but typically this happens before work or in a location where I can’t really start ‘working on my car’. But who knows i’ll get the chance some saturday orso.

I’ve had the plugs out several times in the past 3 months, they all look similar, light brownish haze over the white porcelain.

The fact that it goes away rather quick, and quicker if you push it a bit harder did also gave me the impression that something is dirty and needs to ‘burn’ clean.

Would a drop of oil in the distributor possibly produce such symptoms? There is some leakage from the valve cover besides it, when checking the oil i typically wipe the bottom of the distributor as well. Could something be making its way in there?

[Rob]

[quote=”college man” post=111738]see if this helps.

http://www.ericthecarguy.com/faq/solving-automotive-performance-issues%5B/quote%5D

Will read that (again) later this weekend.

[Rob]

update: the problem is occurring more frequent, thursday even before and after work. And then this morning. This time however i had the time and the tools to look in to it.

Detaching the electrical connector from injector nr 1 (or is it nr 4..) produces pretty much no difference in how rough it runs. Removing any of the others nearly stalls the engine.

Took out the plug on the affected and found this:
[IMG]http://i.imgur.com/Zo7hrJ8.jpg[/IMG]
liquid oil all over the ‘lip’, the electrode etc.

So I fear Grg8888 was thinking along the right lines on this one. It doesn’t look or smells as if its burning a lot of oil while idling/driving (i’ve asked someone to drive behind me and take a look), but the oil was on minimum. Somewhat surprised me as i haven’t been driving all that much in the past months (more like 400 km a week instead of a 1000 km, much shorter trips). Oil has been changed some 6 weeks ago, didn’t fill it quite to the maximum, but probably wasn’t off by a long way. Hard to put a figure on it, but the consumption is certainly rising.

I think leakage along the valves is more likely then a messed up piston ring/wall, since it runs absolutely fine when all cylinders get going. No vibrations or anything. Mate of mine has the same engine in an other car, i’ve had a carbureted version of this engine before so i think i got somewhat of a reference as to how good it can/should be doing. I guess a compression test would be a good idea, but i doubt i’ll learn much.

anything to be done to prolong the life of this engine or get a more accurate diagnosis? As said, shes and old banged up little car. Invested some 150 to get it to pass the yearly check up, I know something isn’t right with the power window switch, the battery won’t likely make it trough this winter.. there is rust on the chassis that will kill it in 2-3 year max, so machine work or complete engine swaps are not an option for this car. (despite my totally ridiculous attachment to this bucket of bolts ;))

[Bill]

It’s hard to say what’s on the spark plug but I wouldn’t rule out coolant. Are you having to add coolant to the system?

[Rob]

Yeah I realized that, added a description below the pic later. But it is quite definitely (liquid) oil on there.

Plug wasn’t exactly new, did just stuck a new plug in that cylinder, just to see how long it takes before that fouls up.

What I don’t understand how ever, is how the problem (used to be) not frequent, while the oil can’t slowly build up there (even when there is enough on there to act up, it gets cleared/burned off within a minute). Or could it just be random, and only leak if its parked with a particular valve opened?

Coolant level is exactly the same as I left it after replacing the radiation 1,5 years ago, thats not going anywhere.

[Lorrin Barth]

What about the weather, notice high humidity when this is happening?

[Rob]

No relation to the weather. It did seem like that a few months ago, hence i’ve been suspicious of my sparkplug leads and distributor too, but as time went on it just appears to be random. Its happened on damp misty mornings, but also on boiling hot sunny afternoons and mostly anything in between.

I’m trying to work out what my options are, if this continues to become more frequent/irritating. Did just watched some of the videos about removing valves in the vehicle, and that would be a lot less work then I assumed it would be to even get to these seals.

But before I start doing that I would like to verify the source of the leaking oil. The valve stem seems to be the most likely source, but really it is nothing more then an assumption.

Should I get a compression tester/have it tested?

Assuming compression is good, should I consider products like leakstop or engine oils with ‘revitalising’ additives, or is that not effective on valve stem seals?

[Lorrin Barth]

A compression test is never a bad idea. Easy to do if you have the tool. However, you are not testing valve seals, only rings and valves. The valve seals are above the combustion chamber and don’t affect compression. The checks for bad valve seals are missing oil, stinky exhaust and a puff of smoke at start up.

I owned a ’92 Mitsubishi and it would wear out a set of valve seals in 100K. By 2003 the problem was fixed but I don’t know where in those years the fix occurred.

The spark plug in your picture looks wet with fuel to me. If that is true then the problem is ignition.

Suggestions: a jug of injector cleaner at the next fill up and maybe a new valve cover gasket. It is amazing how much oil can go through what looks like a small leak.

[Rob]

Thanks for the reply 🙂

I don’t have a compression tester, but I’m considering to get one as I’m sure it proof to be useful in the future. Also for the motorcycle and possibly vehicles i’d consider to buy.

I understand this doesn’t tests the stem seals at all, but it seems like a good idea to rule out a broken piston ring, as that too could introduce oil in to the cylinder. And just see how it holds up to the specifications before taking anything apart. And i’d actually need a hose with a fitting for the sparkplug hole, to even be able to remove my valve spring in the car at all.

I understand I might be wrong in my assessment of the liquid on the spark plug being oil. I have not cleaned up the plug since I took that picture, just stuck it behind some elastic band on a bag in the booth and installed a new plug. If that was fuel or coolant, I expect it to be vaporised by now, and the plugs to be dry.. if its still wet and greasy now 24h later (the oil is maybe 1000 miles old, it still has a nice golden/light brown color) I think it would be safe to assume it indeed is oil. I’ll go have a look in a bit.

Also I have to say external oil leaks appear to be under control, the valve cover gasket is replaced about 3-4 months ago. They are notorious for leaking apparently, and I must admit it has taken several times of additional tightening the bolts a bit, but there is no oil leaking in to the spark plug wells or near ignition parts since i’ve opened this thread.

Injector cleaning is something to be considered perhaps, specially if it indeed is fuel on the plug. I’ll go look at the plug in a bit, that should help to diagnose if its an oil leak or a fuel leak i’d say.

[Author]

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