Well thank you, I didnt mean to say Dex Cool was the problem if I did say so, I was just trying to repeat what I read in another thread but I remember now somebody saying it was GM's fault.

Speaking of torque specs and such, could someone link a DIY article or something with the proper torque specs on all the nuts and bolts on the intake manifold please?

Thank you

 

This article is pretty good: D-tips


This image is straight out the the "dealer issue" shop manual, read the fine print:

 

Thank you

 

Well we replaced the intake manifold and valve cover gaskets. Took all day, but it took care of the intake manifold leaks.

I'm still having the P172, P175 codes come up and P128 also. I've been trying to find more information about the P128 code to see if it has anything to do with the system too rich codes P172 and P175 but I havent found much besides:

Cooling System Issues

• The thermostat is missing.
• Incorrect temperature thermostat is being used. In other words, you're using a lower temperature rated thermostat instead of the stock 195° F rated thermostat.
• Coolant Temperature Sensor is not reporting the correct temperature. More specifically, it's reporting a cooler temperature than normal. The cooler the temperature reported, the more Fuel the PCM dumps.

from this website Part 4 -P0172, P0175 Testing Tips (GM 4.3L, 5.0L, 5.7L)

So I was curious if I should replace my thermostat, or IAT and ECT sensors? Before wasting the money on those, how exactly do I check them to see if they're faulty? One person suggested I use a scan tool to verify the sensors are working but what should I look for when I use one? And how do I diagnose a faulty thermostat?

 

What order were the DTC's retrieved? (Was the P0128 first or the P0172 or P0175?)

If the thermostat is stuck open, or it doesn't close all the way, it will set the P0128 and cause a richer fuel mixture. If the IAT or ECT are out of range, they will set their own DTC in memory. If they are within their normal operating range, and reporting incorrectly, they might not set a DTC. If they report lower than the actual temperature, especially the ECT, it will also cause a rich fuel mixture.

IAT & ECT sensors can be tested with a scan tool that shows streaming data. After the vehicle sets overnight, before you start it, (engine temperature stabilized with ambient temperature) connect the scan tool, turn the key to the RUN position, (don't start the engine). IAT & ECT should both be within 2 or 3 degrees of ambient temperature. If one, or both of the sensors does not, there's a problem. Then start the engine and bring it to operating temperature. The ECT should show ~198F to 202F. If not, the problem is probably a faulty thermostat. The IAT naturally reads a few degrees above ambient temperature due to the added heat radiating from the engine.

 

Here's how they were listed in the scan tool:
P175
P172
P128
P172
P175
P327

I don't own a scan tool of my own, each time I've checked my codes I've gone to Advance Auto Parts or Orielly's Auto Parts stores so can you check the thermostat and IAT/ECT sensors after the truck has been running for say ten minutes, that'd be how long it would take me to get to the Advance Auto Parts store nearest to my house?

 

Nope, starting the engine, even for a moment, skews the test results. Both sensors, along with engine coolant, need to be the same temperature and stabilzed with ambient temperature so you can compare the three. You could camp out in their parking lot overnight, or it might be time to think about adding a scan tool to your tool box You can get an entry level one that will allow you to view streaming powertrain data, on a limited number of circuits, for a couple hundred bucks.

 

When you say IAT & ECT should both be within 2 or 3 degrees of ambient temperature. If one, or both of the sensors does not, there's a problem. Does that mean if one or both arent within a few degrees of ambient temperature then I need to replace one or both sensors?

And when you said The IAT naturally reads a few degrees above ambient temperature due to the added heat radiating from the engine. Do you mean the IAT will always be a few degrees above ambient temperature with the truck both running and off?

 

1) It means we need to diagnose why it/they aren't reporting correctly.

2) The IAT will indicate higher than ambient temp when the engine is running due to the heat radiating from the engine. When the engine is off, if there is any heat radiating from the engine, the IAT will indicate higher than ambient temperature. This is why you need to check IAT & ECT when the engine temperature is stabilized, (equalized) with ambient temperature. Usually takes ~8 hours.

 

I changed the Thermostat and I no longer get the P128 code, and the Temperature gauge on the dashboard goes back up to where it's suppose to. Still running rich apparently?

Well I checked with the scan tool before starting my truck, the temperature outside today was 44F and the ECT and IAT sensor readings showed 41F.

Here are all the Live Data readings before starting my truck:
DTC_CNT: 0
FUELSYS2: CL
FUELSYS2: CL
LOAD_PCT(%): 0
ECT(F): 41
SHRTFT1(%): 0
LONGFT1(%): -1.6
SHRTFT2(%): 0
LONGFT2(%): -1.6
MAP(inHg): 29.5
RPM(/min): 0
VSS(mph): 0
SPARKADV(.): 0
IAT(F): 41
MAF(lb/min): 0
TP(%): 0
O2B1S1(v): .445
SHRTFTB1S1(%): 0
O2B1S2(V): .445
O2B2S1(V): .445
SHRTFTB2S1(%): 0

After checking that I went for a drive to bring it up to operating temperature. My service light came back on while driving. So I got back to the auto parts store and check the codes and live data.

The codes were listed like this:
P172
P175
P172
P175

Here are all the Live Data readings after driving with the service light on my truck:
DTC_CNT: 2
FUELSYS2: CL
FUELSYS2: CL
LOAD_PCT(%): 2.7
ECT(F): 194
SHRTFT1(%): This bounced around from .8 1.6 and 2.3
LONGFT1(%): -10.9
SHRTFT2(%): 0.0
LONGFT2(%): -10.9
MAP(inHg): 10.0
RPM(/min): 630
VSS(mph): 0
SPARKADV(.): 16
IAT(F): 90
MAF(lb/min): .632
TP(%): 0.0
O2B1S1(v): this bounced around from .085, .135, .465, .570, and .755
SHRTFTB1S1(%): this bounced around from .8 1.6 2.3
O2B1S2(V): .725 and .730
O2B2S1(V): this bounced around from .080, .130, .250, .640, and .705
SHRTFTB2S1(%): this bounced around from 0.0, .8, and 1.6

Now after clearing the codes I ran the live data again and noticed a few differences:

SHRTFT1(%): this bounced around from -.8, -1.6, and -2.3
SPARKADV(.): this bounced around from 16, 17, 18, and 19
SHRTFTB1S1(%): this bounced around from -.8, -1.6, and -2.3

Everything else had the same reading give or take a few numbers difference.

Right now I was letting my truck cool off so I check some things out without burning my fingers. I was thinking that maybe there's some kind of electrical problem with the wires or something. So I was thinking if something isnt mounted down where it should be then it's bouncing around when I'm driving fast and giving off the wrong readings and causing the rich condition?

Looking for any advice to what could be causing the problem, I appreciate.

Thanks