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2004 chevy trailblazer_lt_ext
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Discussion Starter · #1 ·
My shitbox (trailblazer i6) has 165k on it I've done plugs, a coil, water pump, fan clutch, and basic service recently.
None have touched on my issue. When cold started and run it randomly stutters and looses power while accelerating.
Kinda like its shifting too early for the next gear, and i can be into the throttle to climb a hill and the rpm will drop 1krpm then come back and when the power comes back on it snaps and its pretty jerky. As soon as the engine reaches operating temp the problem completely disappears and it drives fine. I have a CEL but its for small evap leak and I've had the same light on for like 4 years now so i don;t think thats related. I've done quite a bit of searching and cant seem to find anything similar on the forums. Any insight would be greatly appreciated.
 

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First, connect a decent OBDII code reader scanner to the OBDII port and see if there are any other current, pending or historical codes present. If you don't you will not be 100 percent sure that the CEL is only for the evap leak.

Second, pull the vacuum line off the fuel pressure regulator and see if any fuel flows out. If no fuel flows out, hook about a 6 foot section of vacuum tubing to it, and then place the other end in your mouth and gently suck to create a vacuum. If you cannot create a vacuum, then the diaphragm has ruptured and you need a new one.

Third, does you engine warm up normally and what does the temperature gauge on the instrument panel indicate?
 

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Discussion Starter · #3 ·
ok i scanned for codes already and all i got was the small evap leak p0442. I will check the regulator tonight, and the engine warms up just fine. On a regular 60 deg morning its at full temp in like 3 min of driving. The needle is just slightly to the left of the center line and never moves from there.
 

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I usually refuse to answer and then I block people who drive "shitboxes" but you might have caught me on a particularly kind day ......

That said : I want to know if the ECM has been toon'd.
 

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Discussion Starter · #5 ·
No it has not been tuned. The whole truck is completely stock aside from Napa replacement parts. It's only a **** box because the New England salt has reclaimed most of the metal from the bottom of the doors down. I have kept up with the maintenance on it, but the frame is in too bad of condition for me to keep dumping money into it. It currently needs brakes, the whole exhaust, and a rear gate door. I just need to keep the wheels turning for the next month or so while i shop around for something new. I feel like this problem is going to be something electrical. It drive just fine then acts like it shifted too early and looses power, then back shifts and bucks and the power comes back on. All while I haven't taken my foot outta the throttle.
 

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Have you tested the fuel pump to make sure it's developing pressure within factory spec (50 - 57 psi)?
 
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