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2002 chevy trailblazer_lt
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15 Posts
Discussion Starter #1 (Edited)
For a while I was getting really bad mpg, and I found out that I had a very, very leaky fuel pressure regulator. I got that replaced again in January because since last July (or around that time) I was still getting really bad mileage. When I first bought the vehicle and up until I got bad mileage, I got about 14-17 city, 17-19 combined and 19-22 for Highway. It all depended upon the driving conditions but it was pretty consistent and good, at least to me.

Well, the first time replacing the FPR I got a little better, but then like I said since last Julyish I have been getting really bad mileage, and very inconsistent. So for example I rarely will get better than 16ish...and it seems inconsistent. It just seems like at times I can be driving and it doesn't take much gas to get somewhere but other times my fuel level drops very fast. I have inspected for leaks and there is none. They did a pressure test when replacing the FPR the second time in January. All good according to them.

What I have known but never thought anything of it was my temperature gauge. It always stays well below 210, where it usually will sit. It will sometimes dip way, way down to in between 100 and 210 and stay there for a bit, even on warmer days. Usually it's sitting 2-3 ticks below 210. Rarely does it get up to 210 or above. What I noticed on the one really hot day we had so far was that it did get above 210 and stayed there (never overheated)...but that was then. We can have warmer days like I said and the temperature never gets above 210. I am planning on replacing the thermostat and the temp sensor (I've heard it's better to replace both since it's hard to tell if it's one or the other, and since you are there why not replace both...

Any suggestions? I've read all around and people have said that when your engine doesn't get to running temp the injectors are giving more fuel so it's burning rich. Makes sense because at times I smell gas a lot easier...like I say there's no leaks. We are going to replace my charcoal canister and my gas vent solenoid since that may help, too...does anyone have any other advice or suggestions? Did I nip this in the bud? It is really starting to bug me because here in MN during May gas prices spiked way high and I ended spending about 500 dollars in gas (I do drive a lot) versus around 200 in March and April...I really want to solve this problem.

And also, while I remember, does getting the PCM update help/solve with anything??? I sometimes get a tick from the fan area when it's idling and I've read it's the PCM update that will solve that...anyone know?


ADDITIONAL: Also when I'm driving, acceleration can be very sluggish...i.e. it will take a lot more pedal to get going and shifting seems slower because of the acceleration...just wanted to add because I read that temperature of the engine can affect that...

Also, sometimes when I go out to start it, it has a little bit of a hard start...not to the point where I'm cranking and cranking but it's a matter of like 4ish seconds that will be the difference.
 

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2003 chevy trailblazer_lt_ext
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11 Posts
I presume no trouble codes? How Many miles are on the truck?

I am concerned that 1) yes your thermostat is stuck open and 2) depending on how long you've ran it, the rich-running condition has affected something else. (clogging the cat, fouling o2 sensors, etc).

Also, I notice you're in Minnesota.. any problems in the winter time with the truck not heating up or taking an extremely long time?
 

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2007 chevy trailblazer_ss_3ss
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767 Posts
Yes, if it's not reaching at least 180 deg or so, the computer thinks it still needs to "warm up" and it will run rich (and possibly idle higher), killing your mpg and hurting performance. The thermostat is a good place to start.
 

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2005 chevy trailblazer_lt
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5 Posts
I was told replacing the thermostat would be a good place to start, so you seem to be on the right track to me.

...have fun with the alternator ;) (I just replaced mine three days ago)
 

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2002 chevy trailblazer_lt
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Discussion Starter #5 (Edited)
I presume no trouble codes? How Many miles are on the truck?

I am concerned that 1) yes your thermostat is stuck open and 2) depending on how long you've ran it, the rich-running condition has affected something else. (clogging the cat, fouling o2 sensors, etc).

Also, I notice you're in Minnesota.. any problems in the winter time with the truck not heating up or taking an extremely long time?
No trouble codes, no. Miles are about 174,200ish.

It's been running for a while like this...yeah, that's my thought, too. I'm pretty sure once I get the temp sensor/thermostat replaced, it probably won't hurt to clean the fuel injectors and check things over. It seems like I can smell exhaust more often now, too...not sure if it's due in part to this or if it's my manifold leaking...not even sure if the exhaust is from my car.

Yep, up here in Minnesnowta, lol...you know, I never really did notice much of a difference. It did get sub zero quite a few times this past winter, and it usually always takes a while. But it was pretty much the same, where it would be way under-cooled. It seems like it produced pretty good heat from the vents but then again it was doing this before winter started so I don't have a memorable heat comparison. :bonk: :bonk: :bonk: :bonk:
 

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2002 chevy trailblazer_lt
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Discussion Starter #6
Yes, if it's not reaching at least 180 deg or so, the computer thinks it still needs to "warm up" and it will run rich (and possibly idle higher), killing your mpg and hurting performance. The thermostat is a good place to start.
I see...it doesn't seem to idle high. But yeah it pretty much will fluctuate which I think would more likely explain the inconsistencies of my mpg
 

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2002 chevy trailblazer_lt
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Discussion Starter #7
I was told replacing the thermostat would be a good place to start, so you seem to be on the right track to me.

...have fun with the alternator ;) (I just replaced mine three days ago)
I heard the alternator is kind of a bugger...although my Dad and I did put a new one in like not soon after I bought it which was 3 years ago. So I don't remember it being to much of a hassle...or if it was, at least we have somewhat of a knowledge... :bonk::bonk::bonk::bonk::bonk:
 
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