cold start problems

[LewisI]

I have a 08 Legacy with ~62kmiles.

I used to drive the car daily until a year ago. Now I just drive the car once or twice a week, and since then it started to have cold start problems.

 

When I start the engine, the engine vibrates and sounds like only 2 or 3 cylinders are firing.

The revs drop almost to a complete stall. Then it revs pretty high up to ~ 2k rpm. As it beggins to warm up the revs go down to ~ 1.5k rmp and it sounds like it starts knocking, then it slightly revs up again.

 

There is a noticeable fuel smell in the exhaust in every cold start.

 

After about a minute the engine warms up and the problems dissapear.

Once it is warm the engine starts fine. with no misfiring and no fuel smell.

 

I did a carbon cleaning with oxyhydrogen, to clean the combustion chamber and the problem remained.

Soon after that I changed the spark plugs and the problem is still present.

Misfiring, fuel smell, a knocking sound.

(The sparkplugs were original from factory and they came out pretty clean, so at least the oxyhidrogen cleaned something.)

 

I have also removed the inyectors to get them inspected and cleaned and the results from the lab were no problems at all from the inyectors.

I was suspecting a leak making the mixture too rich.

 

Has anyone had similar issues? Any help is greatly appreciated.

 

Is it possible that ignition coils fail only during cold start?

Can't figure out why the engine is fine when warm.

Should I start replacing sensors?

 

Thanks!

[AShoe]

Oxyhydrogen? Is that fancy speak for you put water in your engine?

 

Do a leakdown test.

[LewisI]

That is no good news, but may explain the problem.

the spark plugs removed were pretty clean, but the threads of at least 2 cyl show burned oil.

 

thanks

[Strizzy]

My guess is that the rubber gaskets between the intake manifold and TGVs make a slight gap when the engine is cold, allowing unmetered air to enter the combustion chamber, causing a lean condition and misfire on multiple cylinders. When the engine warms up, the gaskets expand and seal the leak.

[Max Capacity]

The two plugs with oil on them could be a valve cover leaking, There should be a seal to keep oil of the tube the spark plugs sits in.

 

Have you cleaned the MAF and IAT sensors behind the air filter ?

 

It also could be the Orange o-rings between the TGV's and the intake manifold as said above.

[LewisI]

The two plugs with oil on them could be a valve cover leaking, There should be a seal to keep oil of the tube the spark plugs sits in.

 

Have you cleaned the MAF and IAT sensors behind the air filter ?

 

It also could be the Orange o-rings between the TGV's and the intake manifold as said above.

 

 

Yes I have already cleaned the MAF.

I also suspect an air leak somewhere as sometimes when it is still cold I press the gas pedal and the revs drop almost to a stall.

But after cleaning the MAF that has not been a consistent failure.

 

Now I regret of doing the carbon cleaning, as I'm not totally sure of the spark plugs state before the cleaning. I'll try to put some pictures to get feedback.

 

The spark plugs tips came out red-orange, not white, which seems to be from fuel additives.

[bmx045]

yeah. it's the intake manifold gaskets, been there done that same problems as you to the T. check my how-to in the walkthrough thread