barely runs when cold

gfbidd

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#1
Make
chev
Model
epica
Year
2005
Miles
120,000 km
Engine
2.5
idling high and low, stalling when cold--random misfire--when warmed up it runs great--new spark plugs, swapped coils, compression is good, fuel pressure is good, kind of at a loss!
 

gfbidd

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#2
forgot to mention! also burns oil but no fouled plugs or smoke!! no leaks either!
 

nickb2

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#3
idling high and low, stalling when cold--random misfire--when warmed up it runs great--new spark plugs, swapped coils, compression is good, fuel pressure is good, kind of at a loss!
Suspect cold vacuum leak. Seals up when hot as materials expand.

Would explain for the random misfire, and loping idle cold.

Put a vac gauge on it after a nights soak in the cold. Record reading cold, then record it again once it start running better hot/warm. That will either confirm or rule it out.

never really heard of an engine burning alot of oil and not smoking AND no fouled plugs. If it's not going out through the combustion chamber, it has to be going somewhere else cuz oil just doesn't evaporate. A small amount of oil burning off is normal over a 5000km time. So what is your idea of burning oil. 1l per 1000km's? Or 1l per 5000kms? Big difference.
 

nickb2

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#4
Next would be to look at the IAC system. Then the EGR system.

If you have live data scanner, also go see ECT and IAT reading after a night cold soak before starting the engine. They should be very similar. If they do not both mimic or are not close to ambient temp, that also is a good starting point to diagnosis.
 

nickb2

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#5
EGR has a intake tube.pipe which has a gasket from that tube to egr itself that likes to leak there when cold. That was another example of two materials not working well for mating surfaces. I have seen that one before on the canada models. Are there any other codes besides the random misfire? lean codes perhaps? p0172?
 

billr

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#6
Off topic, but FYI Nickb2:

The Saturn S-series engine is infamous for burning oil without fouling plugs or obvious smoking. 1 qt. per 1000 miles is considered to be normal; even "good" by some. It is the piston design, I will elaborate if you desire to know more.
 

nickb2

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#8
While being off topic, worst oil burning car I ever owned, doge colts. I loved those things, so I bought three of them. But the valve guides would seep down letting oil pass there instead of the stem oil seal. That to was a known one too. But these things were very awful to drive when the guide went south, yeah, pun intended. You could also pick the crust of burnt oil off the spark plugs with a toothpick.

Maybe my example is drastic, but any engine I have worked on with excessive oil consumption had some sort of oil deposits on the plugs.

Can't say I have worked on many saturns, these polymer cars weren't popular up here. That polymer broke like glass at frigid temps. The insurance on these cars was high cuz of the polymer panels.

I would like to know which piston design they used caused this Bill, if you don't mind. I am always up to knowing something new.

My grand pa always told me the only stupid question is the one that was/is not asked. ;)
 

nickb2

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#9
sorry for caps

But in ANY ENGINE, I FIND 1LITER OF OIL FOR 1000KILOMETERS IS EXCESSIVE.

1 quart for 1000miles I find moderate and needs a mention of (needs regular follow ups) on work order. 1 quart for 3000miles, or 1liter for 5000kms is the norm for acceptable in the industry (no follow up needed).

So until OP chimes back on a comment of what amount it is burning, I can't really discus that without knowing what these particular ngine have about them that they clean burn oil.
 

nickb2

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#10
Oh, yeah, were talking about an epica 2005,. Off topic got me going way elsewhere. Back on track here.

Still waiting for op to chime in on more major symptoms of stalling and such.
 

gfbidd

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#11
1 litre per 1000km or more. Will check for vac leaks when I get back to it next week. Yes, there is also a lean code. Thanx for the input everyone
 

billr

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#12
Most pistons have holes drilled from the bottom of the oil-ring groove into the inside of the piston; those Saturns don't have those holes. The holes allow excesss oil scraped off by the oil rings to flow back into the crankcase. Without those, the oil that stays there gets cooked and makes the oil rings stick, then they don't properly even scrape off the excess oil, it remains on the cylinder wall to get burned. Aftermarket pistons do have the holes, and stock ones can be easily drilled, no real precision is needed. The good news is that because everything in that area is "well oiled", wear on the pistons/rings/bore is usually nil on these engines. I think leaving those holes out was a caution to avoid any chance of problems like they had with the Vega engine; even though the Saturn has iron liners and the Vega was aluminum bores.
 

nickb2

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#13
1 litre per 1000km or more. Will check for vac leaks when I get back to it next week. Yes, there is also a lean code. Thanx for the input everyone
also, make sure to check pcv action, could be full on stuck open. Somehow, I kinda knew there had to be a lean code in there. ;) Confirms your probably looking for a vac leak.

The holes allow excesss oil scraped off by the oil rings to flow back into the crankcase. Without those, the oil that stays there gets cooked and makes the oil rings stick, then they don't properly even scrape off the excess oil, it remains on the cylinder wall to get burned.
This I knew.

Saturns don't have those holes.
This I did not.
 

grcauto

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#14
idling high and low, stalling when cold--random misfire--when warmed up it runs great--new spark plugs, swapped coils, compression is good, fuel pressure is good, kind of at a loss!
If this has been asked and answered forgive me. Have you looked at the temperature sensors when cold and watch as the engine warms up?
 

nickb2

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#15
If you have live data scanner, also go see ECT and IAT reading after a night cold soak before starting the engine. They should be very similar. If they do not both mimic or are not close to ambient temp, that also is a good starting point to diagnosis.
I kind of asked that, still waiting on a response.