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2003 chevy trailblazer_lt
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20 Posts
Discussion Starter · #1 ·
Ok fellow Trailvoyers I got a tough one i need help with.

I am having an engine stutter on occasion when accelerating from a stop. It happens only occasionally and intermittently. Doesn't seem related to weather or temperature. And it's only for a quick half second and then drives fine.

Next, fuel economy has been slightly worse and it seems to lack "passing power" at highway speeds. Just a general feeling of lack of "umph" if you will.

I have cleaned the TB (and reset it...plus that was thousands of miles ago now), I have replaced the spark plugs (and a busted coil pack while doing it). The wire clips are fine, but many are missing the clipping mechanism to hold them tight. They seem to stay connected well enough though.

I have a new catalytic converter on it (mine went bad and I replaced it... I was hoping it was the cause of the poor power & hesitation).

I've ran fuel cleaner through it multiple times. I've also replaced the fuel filter (in line...not sure if there is one in the gas tank).

Air filter appears to be in reasonable condition though admittedly I have not replaced it (seems like there is still plenty of useful life in it so I'm thinking it's not that).

I wondered if it was a bad MAP, but I gave that a test by pulling the MAP wire while idling and the engine died so the MAP is still working.

I don't hear or see any places where a vacuum leak might be occurring.

I considered fuel pressure, but I tried to use a scan tool and get "no data" when I try to read "fuel pressure". Maybe these trailblazers don't have a sensor for fuel pressure reading???

These cars don't have a MAF sensor to clean so that's out. Also don't have a TPS (at least not in the traditional sense though I'm guessing the little bulge at the top of the throttle body is a TPS equivalent)

And finally, I HAVE NO SES light on to help figure this out.

Any ideas on what to check? I'd like to not go blindly replacing tons of parts hoping to find a solution.
 

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2003 chevy trailblazer_lt
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20 Posts
Discussion Starter · #3 ·
Potential fix confirmed

So I did the throttle body clean out like 9 months ago. After doing it, I found an idle relearn series of things that had to do with pulling fuses etc. Seemed quick and easy and recommended so that's what I did. There were a few odd things occuring with the car at the time so the rough idle and poor acceleration that ensued was chaulked up to the other issues. I've been slowly fixing them over time and have all engine codes cleared...yet it's still had hesitation and poor acceleration.

As originally mentioned, I did all the obvious stuff and without an engine code it was hard to figure something out.

I've been at the point where I'll just fork over the money and replace the MAP sensor even though I know it's not bad (I just have been thinking it's "intermittent"). Anyway, I happened across a post about the Idle Relearn again, but this time it was different. It stated...

It says to turn the car complete off (remove the key), remove power from the ECM for 20 seconds and then start the car.
Let it idle for 10 minutes.
Shut it off for 20 seconds and then start it and let it run for 5 minutes.
Shut it off again and you're done.

I removed power by disconnecting the battery and I left it for about 15 minutes while I did something else. Then I followed the procedure exactly.

I THINK IT WORKED! I have only drive it a short distance and a more thorough drive tomorrow will certainly be more telling, but it immediately felt more powerful and responsive. It's a damn crazy thing to think this simple thing could have made all this difference that has been killing my MPGs and power for the last forever amount of months it seems.

I'll report more later.:woohoo:
 

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2003 gmc envoy_slt
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628 Posts
Do you have a scanner that reads live data?

You may not have a CEL, but things could still be off enough to cause your problems.

I'd like to know what the Long & Short term fuel trims are.
 

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2003 chevy trailblazer_lt
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20 Posts
Discussion Starter · #6 ·
SOLVED - Update - Seems to be back to normal.

The stumble is basically gone from my car so it appears this extended battery disconnect has made a world of difference. It generally feels more powerful too though there are still times it seems to feel a touch boggy, but hey it's a 6 cylinder engine in an SUV that has 180,000 miles so I can't expect it to be a sports car anyway right?!?

After this unplug I did start experiencing all the damn issues with the AC that people know about. First it didn't work at all. I pulled the fuses and then got it to turn back on but then it was doing the loud grinding/clicking/buzzing deal it does when the actuators are maxing out. Couldn't get it to stop despite resetting it. I even pulled every single HVAC fuse in the rear panel I could find. Still did it. Finally pulled the battery cable again for about 10 minutes, then re-connected and followed the process. I still get about a .5 second buzz if the AC is on when I start the car, but its ok. Anything is better than the 30 or 40 second buzz it did before.

The ONLY outstanding item now is to run through a couple tanks of gas to see if my fuel economy has improved. I imagine the additional power and "umph" i get will improve it, but by how much I don't know. Time will tell.
 
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