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Discussion Starter · #1 ·
I have an 02 TrailBlazer that when I start it, it starts in high RPMS and then calms down. Whenever I hit the gas it's loud and higher RPMS until I'm at a steady speed. I've been told it could be the fan motor? It does sound like the fan is always running. Any ideas?
 

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2004 gmc envoy_sle
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Are you referring to a cold start situation or any time? At cold start my truck jumps up to about 1500 rpm, then after a few seconds down to about 1000 until it's up to temp more then down to 600 or so.
 

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Discussion Starter · #3 ·
It is worse with cold start, but I've gone on 4 hour road trip where it still runs pretty high. It sounds much better after the temp is up and say I turn the truck off, go adn start it again in an hour it isn't as high or loud.
 

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It is worse with cold start, but I've gone on 4 hour road trip where it still runs pretty high. It sounds much better after the temp is up and say I turn the truck off, go adn start it again in an hour it isn't as high or loud.
So is the engine actually running high by looking at your tach, or do you think it sounds high (which would be the fan clutch probably).
 

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The engine runs high - by looking at the tach
Ok. Then I agree. If no codes have been thrown, I'd start with a TB cleaning too. Couldn't hurt and probably needs done. BTW-Welcome:thumbsup:
 

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2003 chevy trailblazer_ls
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normally....
cold engine- 1st thing in the morning.. turn on.. engine revvs up to about 1500 rpm. at this time- you also hear the fan clutch/fan making noise- as it pulls air. (the oil inside has settled to the bottom of the clutch) so it spins at engine speed. depending on outside temp- the oil begins to be distributed inside the clutch- the colder the outside temp- the longer it takes the oil to move around.
so the engine revvs high for a bit- and eventually begins to drop little by little. this is about 2 minutes (to reach about 600).
I never shift into drive or reverse while its above 1000.
Once it drops anywhere between 600-900- I then shift.

But the engine revvs higher than 600 until it warms up a bit.
in colder climates I think this will take a little while until it reaches a warm temp.
Here in Los Angeles- I let it revv down to 600-900 and then shift into drive- and drive gently for 2 miles or so. Once I reach 210- I drive normal.
for me- the fan quiets down withing 20 seconds.
some report up to a minute or more.

If your fan is sounding loud for 10-20 minutes-- then its not working properly.
 

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:iagree: Clean the throttle body and check the fan clutch.

Also, check where your temperature gauge sits. It could be possible that your thermostat may be faulty. Your engine may cool down to fast therefore making it a cold start everytime you start the engine.

It should sit at 210 Exactly when fully warmed up.
 

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2005 chevy trailblazer_ls_ext
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normally....
cold engine- 1st thing in the morning.. turn on.. engine revvs up to about 1500 rpm.
That must be another thing they changed between model years. I've seen others with earlier models say this too - that is their engine runs at 1500 RPM on a cold start.

I've never seen mine go over 1200 RPMS when it's cold. I've had it in "cold country" were the temps with in the low teens and it did the same thing.

Mine will idle down to about 900 RPMS within about 20 - 30 seconds at the most.
I agree - I wait until then to put it in drive or reserve.
 

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That must be another thing they changed between model years. I've seen others with earlier models say this too - that is their engine runs at 1500 RPM on a cold start.

I've never seen mine go over 1200 RPMS when it's cold. I've had it in "cold country" were the temps with in the low teens and it did the same thing.

Mine will idle down to about 900 RPMS within about 20 - 30 seconds at the most.
I agree - I wait until then to put it in drive or reserve.
I think so. My grandfather in-law has an '06 TB and his doesn't rev up as high as mine during startup. On an interesting side note, my '08 silverado seems to change it's cold start rpm based on temp. When it's really cold out, it doesn't rev up much over 1100 or so, but on warm days higher around 14-1500. This may have to do with thick oil also, but it seems PCM controlled.
 

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That must be another thing they changed between model years. I've seen others with earlier models say this too - that is their engine runs at 1500 RPM on a cold start.

I've never seen mine go over 1200 RPMS when it's cold. I've had it in "cold country" were the temps with in the low teens and it did the same thing.

Mine will idle down to about 900 RPMS within about 20 - 30 seconds at the most.
I agree - I wait until then to put it in drive or reserve.
I will double check were mine goes up to....
actually, ill go down and try it right now..
not completely cold-- been sitting for 7 hours...
 

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ok just tried it- appears to sit at 1250 rpm.
so yeah most likely 1200.
Ill try it one of these day with my scanner- and graph it so that I can see how long it takes to reach 1000 and then down to 600.
 
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