New T-stat and CTS, gauge still reading low... - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



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OEM Issues Original Equipment Repairs and/or Problems

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  #1  
Old 11-21-2011, 12:10 AM
blown4pt3 blown4pt3 is offline
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2003 Chevy TrailBlazer LS
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Join Date: Nov 2007
Location: Southwest MI
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New T-stat and CTS, gauge still reading low...

Ok, few things first. Read thru tons of threads on the fan, thermostat, and coolant temp sensors. And yes, I do know I need to get it scanned to read actual coolant temps and I'm working on that.

With that being said, I'm not sure what else to search for so I'll just ask.

Here is the problem, it "appears" to be running a tad cool (1 to 1.5 lines below 210). And even though I didn't get any codes, I replaced the stat because it was about 3 lines low. New stat is an ACDelco, as Autozone has just been crap (on the 4th stat now, factory lasted 4 years).

Have the original clutch that came on the truck when it was built, 155k and has not ever "stuck on" or not turned on and off as it should. Still have the factory O2 sensors, factory cat, and plugs have been replaced with the ACDelco's (2x)s.

After driving a few miles after it is "up to temp" (meaning as warm as it gets), I do have a whine that is RPM dependant, sounds a lot like a gear drive timing set but not as loud. Checked the idler pulley and tensioner pulley, bearings feel smooth, no movement or play, but since they are factory I have ACDelco replacements on order. No noticable loss in power, will shift at ~6k full throttle.

I do have a PCM4less tune. Not sure if it is coincidence or not, but the fan does NOT tick on cold days anymore. Noticed that late last winter and again this year now that it has been cold enough.

Other than t-stat, I have not had most of the issues others have had here. Even after 155k, it still runs good. But mileage is still down about 3 mpgs around town and 3 to 4 on the highway.

Hence the reason why I think it is running cool. However, since the fan is no longer ticking, is it possible to be not disengaging enough at all speeds/RPM? Keep in mind, I have no codes, just seeming to run a little cool and a bit low on the mpgs.

I don't mind buying parts, but don't want to waste money either. Any ideas of things to check or test would be appreciated.

Also FYI, it has the factory water pump, alt, PS pump, AC compressor... hasn't required many parts to be replaced. Heck, even the pass. side wheel bearing/ball joints are factory but has just started going bad and will be replaced this upcoming weekend.
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  #2  
Old 11-21-2011, 11:43 PM
blown4pt3 blown4pt3 is offline
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Time allowing, I'll scan the temps tomorrow to confirm.

In the meantime, has anyone else had problems with getting their motor up to temp after replacing the t-stat and CTS? This one has me stumped and I'm hopeful someone can give me a few other things to check. Is there a hotter thermostat available? I haven't found one, but if someone knows of one I'd like to try it. It is possible I have yet another bad one, but after replacing 3 of them over the years and it never running with the needle "straight up" like it did before the factory one crapped out, I don't want to keep replacing them only to have the same problem.

The fan keeps coming back to mind, however, I'm struggling with the thought that the fan is keeping it too cool because the thermostat would have to start opening to reduce temperatures. If the fan was the problem and running more than it should, but the thermostat is closed, then very little flow should be going through the motor and it should still warm up to ~200. Is my logic and understanding here wrong???

Been thinking of blocking part of the radiator. Even if it does help, its a band aid.
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  #3  
Old 11-22-2011, 09:30 AM
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bromanjr bromanjr is offline
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Quote:
Originally Posted by blown4pt3 View Post
Ok, few things first. Read thru tons of threads on the fan, thermostat, and coolant temp sensors. And yes, I do know I need to get it scanned to read actual coolant temps and I'm working on that.

With that being said, I'm not sure what else to search for so I'll just ask.

Here is the problem, it "appears" to be running a tad cool (1 to 1.5 lines below 210). And even though I didn't get any codes, I replaced the stat because it was about 3 lines low. New stat is an ACDelco, as Autozone has just been crap (on the 4th stat now, factory lasted 4 years).

Have the original clutch that came on the truck when it was built, 155k and has not ever "stuck on" or not turned on and off as it should. Still have the factory O2 sensors, factory cat, and plugs have been replaced with the ACDelco's (2x)s.

After driving a few miles after it is "up to temp" (meaning as warm as it gets), I do have a whine that is RPM dependant, sounds a lot like a gear drive timing set but not as loud. Checked the idler pulley and tensioner pulley, bearings feel smooth, no movement or play, but since they are factory I have ACDelco replacements on order. No noticable loss in power, will shift at ~6k full throttle.

I do have a PCM4less tune. Not sure if it is coincidence or not, but the fan does NOT tick on cold days anymore. Noticed that late last winter and again this year now that it has been cold enough.

Other than t-stat, I have not had most of the issues others have had here. Even after 155k, it still runs good. But mileage is still down about 3 mpgs around town and 3 to 4 on the highway.

Hence the reason why I think it is running cool. However, since the fan is no longer ticking, is it possible to be not disengaging enough at all speeds/RPM? Keep in mind, I have no codes, just seeming to run a little cool and a bit low on the mpgs.

I don't mind buying parts, but don't want to waste money either. Any ideas of things to check or test would be appreciated.

Also FYI, it has the factory water pump, alt, PS pump, AC compressor... hasn't required many parts to be replaced. Heck, even the pass. side wheel bearing/ball joints are factory but has just started going bad and will be replaced this upcoming weekend.
If multiple stats have been installed and your temp always reads low and has been getting lower, then change the sensor, they do go bad.

A confirmation with a scan tool that shows low temps would confirm it.

You are correct that the fan only cools what the thermostat sends to the radiator.
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  #4  
Old 11-22-2011, 11:11 AM
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Ralph_T Ralph_T is offline
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Being a 2003 I would confirm that you have the PCM update that came out in 2005 and also the new fan clutch if it is stuck. Also verify that the IAT sensor is working properly as the CTS and IAT work together to tell the PCM proper amount of gas for cold engine startup. Also make sure you have run some Techron through you system, the air filter and throttle body are clean and you have no vacuum leaks. I would also replace the radiator cap as well as the hoses if needed.
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  #5  
Old 11-22-2011, 11:41 PM
blown4pt3 blown4pt3 is offline
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Scanned the temps

The absolute highest it would reach was 196 with the heater off, sitting in park at idle. If the heater was on, it would drop to the mid 180s. If I raised the RPMs to 2500 and hold it, the temp would drop to the mid 180s. Driving down the road with the heater on, its drops down in the upper 170s, maybe 180. That is with an outside temperature of about 42 to 44F.

So as of right now, even with the new thermostat and coolant temperature sensor, it is running 20 to 25 degrees cold going down the road. The dash gauge appears to reflect this as well.

I haven't checked the IAT sensor yet. Not sure if what it is reading is close to the outdoor temp. The blazer does have an Airaid CAI on it. Checked the computer again and the only fault that showed up was for the ABS, which I would expect having the driver's side front wheel bearing failed. The passenger side is now just about toast, but the replacement came in today and I'll change it this Friday. That obviously has no impact on this problem.

With EFILIve, the PID's didn't let me select an oxygen sensor trim table that showed anything meaniful. When I did select the long term fuel trim it would just show -100. Does that mean anything to someone? I'm real close to putting in an extra wideband I have and watching it.

The throttle body was cleaned when I put in new ACDelco plugs about 2k ago. The air filter is a little dirty and could use a cleaning. When I cleaned the throttle body, I did not replace the o ring seal. At an idle, the computer was showing the throttle position at 4%. Does this make sense???

The PCM does have the latest updates. However, I still have the original clutch fan.

This running cool and poor mileage is driving me nuts. Anybody that has any ideas of what else to check or any info I forgot to mention, please let me know. It sure seems if it were running hot, it would be a lot easier to fix. Seems like after a thermostat and CTS that everyone I talk to doesn't have any ideas.

About the only thing I can think of next is to buy another thermostat, use a thermometer, and measure the temperature where it starts to open at in a pot of water on the stove. 190 degrees in a pot of water should be equal to 190 in an engine. Its not often, but I'm totally stumped!!!

The thermostat is supposed to start opening at 190, according to all info I can find. Running at 175 to 180, tells me it should still be closed. So how can the engine not warm up enough to start opening the thermostat? I haven't done the hot water test to verify on the new thermostat, however, my TB has not run with the gauge straight up since before the original thermostat failed. At one time many years ago, it would warm up and run with the needle straight up pointing at 210. And I also got the best mileage I had with it, at 22mpg on the highway. It was acceptable to me. That was also with the BFG Longtrail OEM tires. I'm currently running a set of stock LS size Blizzacks.

Replace the T-stat again? Replace the O2 sensors? Replace the cat? Replace the water pump? I really like me TB and don't want to get rid of it.

As a side note, the engine is quite rough starting at 1500 and lasts to about 2500. I have a original PCM as well, but it currently is still a brick due to EFILive trashing it. But this same problem existed with the previous thermostats, stock ECM, and stock calibration. For the fun of it, I may send it to PCM4Less and see if they can unbrick it.

Roadie, I greatly respect your knowledge... do you or anyone else have anything to help? This thing is going to make me turn grey!
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  #6  
Old 11-23-2011, 08:44 AM
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Chickenhawk Chickenhawk is offline
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Well, if the coolant temp sensor was a good one, I would still be very suspicious of that thermostat. There is no way it should be reading that low. Plus, a good thermostat should keep the temps VERY steady (the cat needs this) even with heater on or off. If I were you, I would replace it again.

One thing some people have tried - but I would NOT recommend this - is to take a piece of wood and carefully hold it against the fan shroud while it is running and warm, to see if you can stop the fan easily. A good fan clutch and a warm engine mean that you can easily stop a turning fan with a little pressure. Some people have even taken a rag and stopped it with their hand. Please, do NOT do this though, because you don't want to get anything caught in a turning fan - especially if your clutch is bad and it is turning with a great deal of force. If you choose to do this at your own risk ... well, let us know what happens. (If you choose to do this, study the shroud with the engine shut off first to find a safe place to try it that will keep all your limbs and clothing away from the turning fan.)

Just make sure you don't have to change your user name to "fourfingers."
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  #7  
Old 11-23-2011, 10:36 AM
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bromanjr bromanjr is offline
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Quote:
Originally Posted by blown4pt3 View Post
The absolute highest it would reach was 196 with the heater off, sitting in park at idle. If the heater was on, it would drop to the mid 180s. If I raised the RPMs to 2500 and hold it, the temp would drop to the mid 180s. Driving down the road with the heater on, its drops down in the upper 170s, maybe 180. That is with an outside temperature of about 42 to 44F.

So as of right now, even with the new thermostat and coolant temperature sensor, it is running 20 to 25 degrees cold going down the road. The dash gauge appears to reflect this as well.

I haven't checked the IAT sensor yet. Not sure if what it is reading is close to the outdoor temp. The blazer does have an Airaid CAI on it. Checked the computer again and the only fault that showed up was for the ABS, which I would expect having the driver's side front wheel bearing failed. The passenger side is now just about toast, but the replacement came in today and I'll change it this Friday. That obviously has no impact on this problem.

With EFILIve, the PID's didn't let me select an oxygen sensor trim table that showed anything meaniful. When I did select the long term fuel trim it would just show -100. Does that mean anything to someone? I'm real close to putting in an extra wideband I have and watching it.

The throttle body was cleaned when I put in new ACDelco plugs about 2k ago. The air filter is a little dirty and could use a cleaning. When I cleaned the throttle body, I did not replace the o ring seal. At an idle, the computer was showing the throttle position at 4%. Does this make sense???

The PCM does have the latest updates. However, I still have the original clutch fan.

This running cool and poor mileage is driving me nuts. Anybody that has any ideas of what else to check or any info I forgot to mention, please let me know. It sure seems if it were running hot, it would be a lot easier to fix. Seems like after a thermostat and CTS that everyone I talk to doesn't have any ideas.

About the only thing I can think of next is to buy another thermostat, use a thermometer, and measure the temperature where it starts to open at in a pot of water on the stove. 190 degrees in a pot of water should be equal to 190 in an engine. Its not often, but I'm totally stumped!!!

The thermostat is supposed to start opening at 190, according to all info I can find. Running at 175 to 180, tells me it should still be closed. So how can the engine not warm up enough to start opening the thermostat? I haven't done the hot water test to verify on the new thermostat, however, my TB has not run with the gauge straight up since before the original thermostat failed. At one time many years ago, it would warm up and run with the needle straight up pointing at 210. And I also got the best mileage I had with it, at 22mpg on the highway. It was acceptable to me. That was also with the BFG Longtrail OEM tires. I'm currently running a set of stock LS size Blizzacks.

Replace the T-stat again? Replace the O2 sensors? Replace the cat? Replace the water pump? I really like me TB and don't want to get rid of it.

As a side note, the engine is quite rough starting at 1500 and lasts to about 2500. I have a original PCM as well, but it currently is still a brick due to EFILive trashing it. But this same problem existed with the previous thermostats, stock ECM, and stock calibration. For the fun of it, I may send it to PCM4Less and see if they can unbrick it.

Roadie, I greatly respect your knowledge... do you or anyone else have anything to help? This thing is going to make me turn grey!
Apologies, I did not see that you replaced the CTS, One other thing to check is the Fuel Pressure Regulator, with the bad mileage and poor idle, it may be leaking and introducing excess fuel into the engine. In rare cases running rich can cause an engine to run cool, but the thermostat has control of the flow. Running that cool could still be a bad thermostat.

To check the FPR, While running, disconnect the small vacuum line to the FPR and check for fuel wetness. Any sign of fuel means the FPR is bad.
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  #8  
Old 12-06-2011, 12:01 AM
blown4pt3 blown4pt3 is offline
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Originally Posted by bromanjr View Post
To check the FPR, While running, disconnect the small vacuum line to the FPR and check for fuel wetness. Any sign of fuel means the FPR is bad.
Thanks, I'll be checking the FPR tomorrow, along with the transfer case fluid. I know its totally unrelated, I'm just going down a list of stuff before the snow starts coming.

I am also running some Techron thru the fuel system. Autozone had a deal, 2 bottles that treat 12 gallons, buy one get one free IIRC. So I ran it till the fuel light was about to turn on, filled with 11 gallons or so, ran it down same way, another 11 gallons and running it out now. I should mention that I typically run either the 87 Shell or 93 Shell. Only 4 or 5 times per year does it get anything other than Shell.

As a side note, I replaced the passenger side wheel hub assembly, upper and lower ball joints, and new sway bar links up front this past weekend. Tonight, I put on a new idler, tensioner pulley, belt and had the front end aligned. Both pulleys were starting to go out. The alternator won't be far behind and only needs to last about 3 weeks.

I have a new clutch fan; will probably install this weekend. After that, probably after the 1st of the year I'll toss in a new water pump, new upper and lower rad hoses, test and ensure a new thermostat works and install along with another new coolant temperature sensor. Then have the whole system flushed. Also tossing around the idea of a transmission flush. Changed the trans filter about 70k ago. Never had a flush. Air filter also needs washed and re-oiled.

2 new O2 sensors, new IAT sensor, new cat conv. and exhaust are also planned for the Jan/Feb time frame. The exhaust seems to flow ok, other than the tweaking of the pipe I did backing into a sloped yard a few weeks ago. Nothing is creased, but it is tweaked enough I'm a little concerned of cracking the exhaust manifold due to the extra forward pressure. Poor mileage was before the ehaust was tweaked and no change since.

Basically, I'm waiting to see if anything I've done in the last week has made any improvement. I can accept 13/14 mpg in town, not 9 or 10 like what it is doing now.
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  #9  
Old 01-07-2013, 11:22 PM
blown4pt3 blown4pt3 is offline
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OK, finally an update after a year.

Replaced the thermostat AGAIN! This is like the 5th or 6th one. This time I tried a Motorad from O'Reillys. At the same time, I also installed an efan kit from PCMforLess. While I was at it, I also replaced the CTS (AGAIN) with another ACDelco unit. To get the original clutch fan out, I had to cut the shaft, so I put a new ACDelco water pump on it.

I did this because the damn thing was still running cool. Anyway, gas mileage is now down to 8 or 9, it runs rough at idle (in gear or not), is low on power, doesnt want to rev above 5k or so in any gear or at WOT. And yes, it did this before replacing the clutch fan, tstat and parts mentioned above. So the parts have made no difference, although the temp is FINALLY running between 190 and 198 (when the fan kicks in)

The TB was cleaned when I changed plugs, about 10k ago. I measured the fuel pressure, it was 56psi, so thats ok.

I took it to an exhaust shop to look at the cat. They said it was ok. I asked what the pressures where, but they didn't pull the O2 and measure it. So that "opinion" is garbage.

I took it to another shop and asked if they could measure the pressure at the O2. The mechanic told me he was "certified" and that no such gauge exists. I started to pull my smart phone out of my pocket, but figured the "free" advice wasn't worth any more of my time. So I left.

Anyway, I ordered this phantom "exhaust back pressure gauge" that doesn't exist and it should be here in 2 or 3 days.

This is exactly why I HATE going anywhere to have anyone work on my stuff. I believe the power issue is a cat problem, although the computer hasn't set a code. I'll report back once I get a change to test it.

Anyway, here is where I do need help. I want to change the front O2 and see a few on Rockauto. Please let me know which ACDelco PN I need to order. Its a SWB '03. Looks like there are 2 or 3.

And if the cat is bad, I plan to install the OEM grade universal fit from Magnaflow. PCMforLess has tuned it to ignore the high flow condition.

I also will measure the resistance of the injectors at the harness, probably this weekend because I have a new TB gasket to install. The original one is sealing OK, but I figure why not because last time I cleaned the TB, I didn't bother to tighten it with a torque wrench like I do with everything else.

And if you are wonder why I hadn't messed to much with it in a year, it is because I bought a 03 ZR2 with 45k and have been driving that instead. Now the wife wants to drive the blazer so it needs to be right.
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  #10  
Old 01-08-2013, 01:42 PM
gstump gstump is offline
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I feel your pain man!

Your loss of power is very likely your cat based on my research and experience with my rig. I had one muffler guy try and tell me that I had two cats and wanted $800 to replace them Did it myself. Big pain but at least it's done and power has been restored. I too still have the low temp issue though so will be following this with great interest as I am in no hurry to replace my cat again. I don't want to hijack your thread but I did replace my fan clutch a few years ago and I think the replaced one runs a bit fast so I am wondering if this might be why the temp is low. Anyway, again, I'm gonna start another thread with that discussion. Luck be with you!
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