Tbi 454 mpg...Is this as good as it gets?

[whiteboyslo]

Found the CTS on my truck. Looks original. I don't have a scan tool, but the ACDelco part is a whopping $15, so what the heck...

Mike

 

[AlexHawk94]

There are probably other versions online, but here is one from lmctruck.com

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Thank you

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[Dave454ss]

9 mpg 454ss? Totally worth it

Cant disagree..Back in the late 90's it was a cool truck. Still is, but performance wise, not so much. Sold my SS to get a 01 Sierra X-Cab 5.3 and without a doubt my 01 was 5x the truck performance wise then my SS...AND got way better MPG.
Its why when I got the itch to "have my RCSB back", I chose a normal one and I'll be LS Swapping it...

 

[whiteboyslo]

***Update***

I replaced the CTS last night. This shows promise. Since the day I brought it home, the truck has shifted pretty firmly on the 1-2. Now it's butter-smooth through all gears! Worth it just for fixing that, but this shows the CTS clearly had issues. Maybe it was running rich because of it? Not sure. I topped the tank this morning and will report back at the end of the week.

For now, just having a super-smooth transmission makes this whole thread worth it.

Mike

 

[biggbiker]

If you guys are concerned about your gas mileage, one thing to verify is that your coolant temperature sensor is reading accurately. I am not talking about the one that screws into the cylinder head and drives the gauge on your dash, but rather the one that is screwed in next to your thermostat. That one beside the thermostat is what your ECM reads.

The one on one of my 1999 Suburbans was reading inaccurately, would never read above 150 f according to my scan tool. The truck has to get to somewhere around 185 to 190 before the ECM begins running the proper fuel-air ratio.

Find a scan tool that can measure what the OBD2 system thinks the coolant temperature is. If you have a 195 thermostat, and you cannot get the OBD system to read at least 188 or higher, it may actually be that hot, but the computer won't know it, and constantly running rich.

What am I missing hear? Both my 1996 ECSB and my 1999 Yukon both 5.7L run @160 degrees F. Both will burn you out of the truck @ -10 below. I assume both are factory thermostates. Anyone ?

 

[redfishsc]

What am I missing hear? Both my 1996 ECSB and my 1999 Yukon both 5.7L run @160 degrees F. Both will burn you out of the truck @ -10 below. I assume both are factory thermostates. Anyone ?

The 5.7 vortec is intended to be used at 195f. Running a 160 most likely means the ECM constantly thinking you are still warming up, and you are running rich all the time.

 

[redfishsc]

What am I missing hear? Both my 1996 ECSB and my 1999 Yukon both 5.7L run @160 degrees F. Both will burn you out of the truck @ -10 below. I assume both are factory thermostates. Anyone ?

Also, are you taking this temperature reading from what's on your dashboard? Every Chevy I've ever had from this generation always reads lower than reality on the dashboard. They all vary in how inaccurate they are, but they are al
Often definitely inaccurate, they always read low.

Verify that your engine computer actually thinks you're running at 160 by measuring the temperature via and OBD2 scanner that can read live data. Or just make sure that your thermostat is a 195 that is functioning properly

Right now I have two of them, one truck always says that it's at about 140, the other one says it's at about 170, but if you hook the scanner up to it, both of them run from 188 to 194 and both have a 195 thermostat

 

[BBSteve]

Hi, the MPG that you are getting is pretty much what to expect with this vehicle. My 88 K3500 with a 454 th400 and 4:10 gears is quite similar even after a intake manifold change,complete exhaust rework (long tube headers, true 2.5 dual exhaust all the way out the back) and a chip. This beast runs great and is a pleasure to drive. I have decided that I am getting Smiles per mile, as opposed to MPG which makes me happy when driving this rig. Long live the gas consuming no overdrive torque monster Big Block chevy. Even old men need to be able to roast the tires at will.10-10.5 MPG is what the norm is on my truck and it has the EVIL STEVE tricks and tune. I have been pouring fuel in these beasts since 1976 and have good grip on what makes them happy. Drive it and you will find that you are always smiling, except at the gas pumps.....................

 

[Supercharged111]

If you guys are concerned about your gas mileage, one thing to verify is that your coolant temperature sensor is reading accurately. I am not talking about the one that screws into the cylinder head and drives the gauge on your dash, but rather the one that is screwed in next to your thermostat. That one beside the thermostat is what your ECM reads.

The one on one of my 1999 Suburbans was reading inaccurately, would never read above 150 f according to my scan tool. The truck has to get to somewhere around 185 to 190 before the ECM begins running the proper fuel-air ratio.

Find a scan tool that can measure what the OBD2 system thinks the coolant temperature is. If you have a 195 thermostat, and you cannot get the OBD system to read at least 188 or higher, it may actually be that hot, but the computer won't know it, and constantly running rich.

Also note, my only experience is the 5.7. I'm assuming the Big Blocks and diesels have a similar scenario that could happen

The key is to verify with the scan tool that the sensor is bad like you did instead of just throwing garbage aftermarket parts after good OEM parts. PCM enters closed loop in the 100-120 range, not 180-195 FYI.

 

[someotherguy]

Also, are you taking this temperature reading from what's on your dashboard? Every Chevy I've ever had from this generation always reads lower than reality on the dashboard. They all vary in how inaccurate they are, but they are al
Often definitely inaccurate, they always read low.

Verify that your engine computer actually thinks you're running at 160 by measuring the temperature via and OBD2 scanner that can read live data. Or just make sure that your thermostat is a 195 that is functioning properly

Right now I have two of them, one truck always says that it's at about 140, the other one says it's at about 170, but if you hook the scanner up to it, both of them run from 188 to 194 and both have a 195 thermostat

Don't depend on the sensor reading as a bad CTS will often report a lower temperature than actual. This is why a failed CTS causes the fuel mixture to be too rich.

Get the actual temperature using an IR thermometer, preferably one with a "max reading" feature, to scan all around the intake at the thermostat housing. Temperature on the intake just below the thermostat will be the actual coolant temperature.

100% agreed the dash gauge is usually wrong, and on the cold side. Once all efforts to be sure the engine is running at proper temperature AND the gauge circuit is in top shape - correct and good sender on the head, good connections, good grounds - next step is "re-pin" the needle on the gauge. Pop the lens off the cluster, get the engine fully warmed up, double-check the temp with the IR thermometer, gently pull the needle off the gauge and re-install it where it should be.

Richard