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Discussion Starter #1
Why does my 05 Trailblazer 4.2 L stall when the engine is level. Replaced front suspension when I drop the truck down engine won't start Jack the front and back up fuel pump and gauges truck runs fine stalls while idling when I drop level again
 

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Discussion Starter #5
Full tank of gas new fuel pump. Had an ABS warning light come on after replacing both front control arms tie rod struts hubs Etc. Other than that no codes runs like a kitten when one end of truck is lifted up.

= Stumped
 

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2002 chevy trailblazer_lt
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Wonder if there is some harness connector or wiring like a ground connection that is getting stressed??
 

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Discussion Starter #7
Yeah same here I checked but did not see anyting. I've gone over every inch of the truck half a dozen times or more. Been going on taking space in my garage about three and a half weeks now. Thought it might be a fuel pump issues so that's why I replaced but got the same results.
 

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In the first post you mention gauges. What happens with the gauges jacked up vs level?
 

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Discussion Starter #9
all gauges are in the green and responding well. Fuel gauge battery temp RPM all very responsive. no check engine light. Had three different scanners plugged in no active or pending codes other than cylinder 2 coil on plug misfire that I replaced a few months ago.
 

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Discussion Starter #10
Would a faulty fuel pressure regulator have any similar symptoms. Only thing in the fuel lines that I haven't checked or replaced
 

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What model year is it, 05? The early models have external fuel pressure regulators but I don't know about the 05. Got an external one? Seems unlikely to cause your issue though really.

Any of your scanners an ELM327? Could look at and record live data to maybe get a clue.
 

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Discussion Starter #12
Yes there is an external fuel pressure regulator purchased one have not yet replaced. Yes have seen live data and everything is in the green right up until the engine dies with no codes while lowering.
 

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Something like this is unlikely to set a code.

Recording live data for review would let you see things like what were the fuel trims at the time, what were the injector firing rates like, where was the timing, what was the throttle doing, and so on.
 

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Odd. Really odd.

Can you replicate the problem by driving up an idling on a slanted driveway and then point your car down it again - assuming it's got some kind of hill, that is.

There's NO way a fuel pump cares if you are even at a 30° 45° forward-to-aft or starboard-to-port angle. If that were so, no-one could drive offroad.

  • I can't think of any stresses that could do this unless your car bends in the middle - but that's not likely either.
  • An Anti-Rollover switch isn't a factor here - even if you had one that is. (GM uses a plastic ball anyway)
  • Electricity to-from pump doesn't care if it runs up or downhill either ... within reason
  • I'd also iggy the fuel pressure regulator here for a while - I don't think it even cares.
  • STFT or LTFT won't matter much here - that's likely a false flag that would require too much time to plot or diagnose anyway. An engine can actually run 'way off the scale for TRIM Variations.
  • I'd just make sure that the fuel pump REMAINS running when you get this problem to act up.
Until you confirm the fuel pump is working yea-or-nay - then you aren't gonna find this logically.
Use a fuel pressure/volume gauge set to affirm this.

Obey a logic tree here.
 
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