I'm going with a 180 since winter is coming. Is shoeboxs tutorial good for the change? I've never done one on these cars

 

Not true. The ECU has a temperature sensor so it knows the operating status, and a temperature compensation fuel map. When it's in closed loop, it's aiming for a targeted fuel ratio anyway.

You'll be perfectly fine running a 160* tstat without programming. I did it for a long time. Highway temps will be lower, otherwise everything else will pretty much be the same since the fans come on at the same temp.

 

The problem with lower coolant temps is not due to the PCM and the coolant temp reduction. The PCM knows the exact air flow into the engine because of the MAF sensor, and proportions the fuel correctly for that air flow.

The problem is that as combustion chamber temps drop, the burn is less complete, so you dump some unburned fuel out the exhaust. But I doubt you will even notice it. You are also throwing away more of the combustion BTU's, since they are being lost to the coolant, so the engine's thermal efficiency drops. But in the case of the LT1, this appears to be offset by the gain in air density due to the reduced heat transfer in the intake manifold.

With the lower coolant temps, you may also be able to add a bit of ignition advance, which may help power and fuel efficiency.

But he has to solve the overheating problem first.

 

Would a temperature that is too low cause it to stay in open loop?

Just curious that you don't have a problem any other time then going at highway speeds and you say you have some sort of grill that is not OEM.

Why not try it with the grill out and see what happens?

You did pull the top support to see if there was debris in between the condenser and the radiator right? FWIW, mine had one of those plastic shopping bags in there.

 

Yes, but the temp is about 90*F. If the coolant temp sensor is bad then yes, you'd have problems, but in normal operation you won't ever get stuck in open loop due to low temp.

 

I looked underneath the car... would pulling the top support be necessary? I have a billet grill... how would that effect the airflow?

 

The changes to the car was Cutout and grill when it started doing it.

 

You Said it is running at 260 on then highway? that is insane you should not be driving it even at 210 that its gonna cause some melting of gaskets. happened to my brother he put a lt1 in his jeep and didnt realize the common temp. fluid has to be getting lost somewhere. or not enough in the system.. check to see if your reserve tank is leaking underneath the battery. is the fluid bubbling out with cap off and car hot? may be a bad waterpump not spinning..

 

Well, some of this is completely wrong. Running at 210f is not going to melt any gaskets. The cooling system is designed so that the fans don't even come on until 226f. As with any engine running hot scenario you
Look for the basics....is the coolant level normal, is there flown the cooling system, is the air flow path blocked, etc. Since the problem started after a mod was performed that's the first logical place to look...

 

I didn't suggest removing it. I suggested you look to see if there was debris there. Sorry if you couldn't infer that I meant to "put it back".


The last statement is the DUH moment.

 

Coolant is full, no leaks. A faulty thermostat looks like it. I'm going to bleed the system one more time. I definitely am changing the tstat and rad cap since there 14yrs old and cheap to replace

 

235 is what its been running on the highway and a bit lower in city..

 

Are you loosing any coolant?Might be a clogged radiator I think.I would take the car in to a mechanic(or radiator shop).Don't blow the car up because of overheating.my02.

 

Sometimes people put the thermostat in upside down in some cars,and can be a problem.My02.