Cannot figure out this idle problem

[Keckster]

This is my oil cooler setup. Has a fan on the back sucking air in from outside the car. My guess is this is heating my intake pipe. I’ll try swapping the fan direction see if it makes a difference

 

[Gtstorey]

I doubt that is the problem. I don't think there is that much heat in the oil. I would check the MAF iat sensor first by seeing how close to ambient it is on a cold start up, followed by a resistance check on the sensor. I can supply the sensor values for the later models but I don't know if they are the same.

 

[Keckster]

It’s a brand new maf. Reads ambient at first start. Plugged in the old maf and that also reads ambient correctly

 

[Desert Sasqwatch]

This is my oil cooler setup. Has a fan on the back sucking air in from outside the car. My guess is this is heating my intake pipe. I’ll try swapping the fan direction see if it makes a difference

Put a piece of tin around the intake pipe to deflect the air coming off the HE, if you think the HE air is contributing to the IAT. Reversing the fan will just pull warm air out of the deadspace between the firewall and the engine.

 

[Ross]

Someone please explain to me why you would put an oil cooler on an LSJ engine. My engineering brain doesn't see the logic. On an old air cooled engine it makes sense.

The LSJ already has an oil heat exchanger stock from Chevy... it exchanges heat with the engine coolant. The engine coolant has a thermostat, and regulates the oil to the correct temperature. Both heating up the oil (cold engine start), and cooling it down. If you are making too much power, and the engine can't keep cool, then add a heat exchanger to the coolant, not the oil. Running cool oil does not lubricate your engine correctly.

You could convert that oil cooler back to a heat exchanger for the intercooler, and keep the intake air temps down.

 

[Keckster]

Someone please explain to me why you would put an oil cooler on an LSJ engine. My engineering brain doesn't see the logic. On an old air cooled engine it makes sense.

The LSJ already has an oil heat exchanger stock from Chevy... it exchanges heat with the engine coolant. The engine coolant has a thermostat, and regulates the oil to the correct temperature. Both heating up the oil (cold engine start), and cooling it down. If you are making too much power, and the engine can't keep cool, then add a heat exchanger to the coolant, not the oil. Running cool oil does not lubricate your engine correctly.

You could convert that oil cooler back to a heat exchanger for the intercooler, and keep the intake air temps down.

I get your points here! I originally had planned to clean up the thermostat housing with my own design to get rid of the ugly loop of hose for what used to be the heater core loop. The oil cooler on my engine had a small crack in it as well so instead of replacing it with stock I guess I got carried away and upgraded to a HE.

 

[Gtstorey]

My oil temp gauge, sensor in the drain plug, never gets above 160 and typically stays in the 150 range. I don’t know what the temp at that location really means, but seems almost too low. This is with a stock setup.

 

[Ross]

My oil temp gauge, sensor in the drain plug, never gets above 160 and typically stays in the 150 range. I don’t know what the temp at that location really means, but seems almost too low. This is with a stock setup.

My engine temperatures seem too low as well. I wonder if the engine coolant thermostat is unable to close completely, or if the bypass drilled hole in the thermostat is too big.
Wait... The interior heater core that we removed, and now is just a loop might be bypassing the thermostat. No wonder the engine can't keep heat in. I need to pinch that heater loop closed, and go for a test run. See if my temperatures get up to normal 220F range rather than 180F.

 

[Keckster]

I believe if you block off the heater core line it stops coolant for flowing all together as the port for coolant to exit the engine only goes to the heater core. I’ll have to find the thread where it was talked about

browsing a bunch of other forums owners say their balts sit around 180-215. Stock fans turn on at 212

 

[Gtstorey]

My engine temps seem fine, pretty much set at 186 which is around my fan temp.

 

[Keckster]

Well, The issues have returned after I chased down that my pcv valve was stuck open. I found the source of my KR from earlier being a bolt that came loose on the HE pump bracket. Now that the engine is all back together I'm struggling to get it to idle down to where it was previously. I've attached a log below on my idle. It is a pretty smooth idle however it keep setting a code and cannot seem to get down to the 950 rpm I have it set to. I've got the MAF dialed in and fuel trims on yet it still won't even attempt to go lower than ~1200rpm. The odd part is, if I go in and set my base idle to 1200 in the tune it'll stay at about 1450. I find it strange that no matter what I set the base idle to it stays about 250rpm higher than supposed to with max timing taken out from the overspeed tables.


ignore the parts of this log above 1800HZ on the MAF. I tried commanding different idle rpm to see what would happen and It caused a bunch of junk data above there.

 

[Gtstorey]

Probably need to post a current version of the tune since it’s been a while

 

[Keckster]

Right right! Here is the latest on the tune. I had put many miles on this before pulling the intake off and fixing the pcv. Notable changes since the last tune I posted is the addition of a boost reference fuel pressure system. The low end of the maf is from today trying to get it to idle properly.

 

[Desert Sasqwatch]

It may be caused by unmetered air getting to the intake manifold through an open port, wrong vacuum hose connection, or gasket leak. The 250 rpm seems very consistent above the idle setting changes made. Since the intake manifold has been disassembled I would lean toward a gasket leak.

 

[Keckster]

It may be caused by unmetered air getting to the intake manifold through an open port, wrong vacuum hose connection, or gasket leak. The 250 rpm seems very consistent above the idle setting changes made. Since the intake manifold has been disassembled I would lean toward a gasket leak.

That’s what I thought at first too. Couldn’t find anything obvious… I don’t have a proper smoke tester so I am open to any recommendations. Tried some hairspray around the intake since I was out of parts cleaner lol. I’ll pick some up in the morning to see if it’ll make a difference

 

[Ross]

Maybe your local auto parts supply store has a smoke tester you can loan. Or maybe you can cobble up the parts for your own smoker.

 

[Gtstorey]

I don't know anything about the Cobalt SC but why have you changed the Idle Airflow settings, especially the min effective area?

And is it currently running MAF only tune and does it work better when running mixed tune or SD only?

Yours

Stock

 

[Keckster]

I don't know anything about the Cobalt SC but why have you changed the Idle Airflow settings, especially the min effective area?

I have changed the ETC scalar a while back because I had trouble with it pulling timing into the negatives at idle. The p12 ECM on the lsj does not have the base running airflow table unlocked in hp tuners and with the larger cam it struggled at low airflow/efficiency. by boosting the ETC scalar I was able to get the timing at idle to come up from negative. I did try changing the ETC back to stock after replacing the pcv but it made the timing even worse and would barely idle even after getting fuel trims to stabilize.

is it currently running MAF only tune and does it work better when running mixed tune or SD only?

Yes I had tried both SD and MAF as well as both to see if either was causing the high rpm/negative timing issues. The tune I uploaded is in MAF only currently as that was where I had to leave off before getting ready for work.

 

[Gtstorey]

What about the min etc area? I would think that would be the same as a vacuum leak since it sounds like that will keep the throttle open more than stock.

 

[Keckster]

What about the min etc area? I would think that would be the same as a vacuum leak since it sounds like that will keep the throttle open more than stock.

I'm not sure what the min ETC area does to be honest. I didn't change that setting, had a guy helping me with tuning a while ago but wasn't working out. I'll try changing it back to zero though tomorrow!