Thermostats—- 160* vs 187*

[Jonesy92]

2003 Tahoe Original Eng/Trans.
298k miles
—Had a recent issue, replaced my failing thermostat, and installed a new one. Temp got up to 187-192, and it never ran that hot. I now also have misfires, lean codes, and hesitation that I didn’t have before. Nothings changed, except the thermostat.
I am wondering, from my past experience, I got a flex fuel fuel filter, which did not fit my truck, and am wondering if they sold me the incorrect/ or flex fuel thermo.

 

[Scottydoggs]

normal operating temp is 210, so the t stat should not be the issue. try the right fuel filter who knows it might be restricting the fuel and running lean and causing the misfires.

 

[SnowDrifter]

how are you measuring temp?

 

[tom3]

What happened to the original thermostat? Running hot? Head gasket?

 

[Jonesy92]

When I bought the truck, the thermo was a 160, but it was worn out, eaten away.
Verifying operating temp I am using my obd2 scanner. I’ve had a compression check done, and also a leak down. Compression check showed well within 10% of each other, and within spec. Leak down was inconclusive and showed no issues. I’ve even bought a smoke tester to check the intake. No luck their either.
Fuel filter was changed, along with fuel pump less than 10k miles ago with the correct one.
I owned a 02 and it ran under 210 for sure. I figure maybe they gave me a higher temp thermo, causing the fuel to almost vaporize before combustion.

 

[Jonesy92]

only reason I suspect the thermo, is I either read an article about the flex vs non flex, and I read they updated to 187* thermo for engine performance/efficiency.

 

[Fless]

I'm not aware of any difference in thermostat temps between Flex and non-Flex. They're both OE 187° temp thermostats. Like @Scottydoggs noted, these engines normally run north of 200°. If you run them cooler than that they're less efficient.

 

[SnowDrifter]

I'd you're running in the 190 range, that's fine. Mine runs in the 194 to 197 range with an oe thermostat
The misfires intrigue me though. What are your bank 1 and 2 fuel trims?

 

[Jonesy92]

I’d have to check when The wife comes home from work. I do have a fuel pressure gauge on its way here for the fuel rail.
Im not having any lean codes, after replacing intake gasket set, and knock sensors.

 

[Jonesy92]

I can get you an idle shirt/long fuel trims @idle rpm, and about 2grand?