Cold start takes longer than normal

mcc

Original poster
Member
Apr 8, 2012
49
Recently my Envoy's been taking a bit longer than normal to turn over from a cold start. 3 solid seconds is the most it's taken so far and it once took over 2sec after driving a couple miles, stopping for 5 minutes, and starting it again. The autostart feature (short key flick) won't crank the engine long enough to cold start the car which leads me to believe that it's out-of-spec. Is this indicative of a problem that could bite me later?

I've tried holding the key at "on" for 20 seconds before starting to build up fuel pressure. That didn't help. I also turned the accessory pulleys by hand while doing the CPAS last weekend and all turned smoothly.

Potentially relevant recent maintenance: (trans/xfer case etc. omitted)

Summer 2011
  • Battery
  • Serpentine belt
April 2012
  • Chevron dino oil w/ cheap filter (Pennzoil Ultra this weekend)
  • 41-103 plugs
  • Weatherstrip mod to keep water out of #4 (preemptive fix)
  • 2x Techron treatments
May
  • Removed and thoroughly cleaned throttle body
  • Fuel filter
  • Air filter
June
  • Thermostat and coolant temp sensor (Delco)
  • Upstream O2 sensor (Delco)
  • Ignition switch (Delco- preemptive replacement)
July
  • Replaced CPAS (GM)

There's ~105k mi on the odometer.
 

CaptainXL

Member
Dec 4, 2011
2,445
Assuming it starts eventually it sounds like a crankshaft position sensor issue. I would check to see if your getting fuel and spark from the getgo first.
 

mcc

Original poster
Member
Apr 8, 2012
49
Yes, it always starts and, with the new CPAS, idles perfectly. Would a bad crankshaft position sensor always throw a code? I should add that I've been checking with Torque and there are no pending or active codes.
 

CaptainXL

Member
Dec 4, 2011
2,445
mcc said:
Yes, it always starts and, with the new CPAS, idles perfectly. Would a bad crankshaft position sensor always throw a code? I should add that I've been checking with Torque and there are no pending or active codes.

Yeah it should set a code. I was just telling you what it seems like not what the problem is. You need to check fuel pressure first and see if your pump, pressure regulator and fuel injections are in working order. If the pressure is good and it holds pressure with koeo for 5 minutes then the injections aren't stuck open.

Also use Torque to check for STFT and LTFT fuel trims. These readings will give you an idea if you have too much or little fuel or too much or too little air
 

Mooseman

Moderator
Dec 4, 2011
25,341
Ottawa, ON
Mine does that once in a very while but usually starts with the key flick. I had a similar issue with my '00 Jimmy and it wound being a bad fuel pump. Check your fuel pressure to see if it builds up before startup. Could be either the fuel pump or pressure regulator.
 

mcc

Original poster
Member
Apr 8, 2012
49
I watched the LTFT and STFT on my commute to my internship this morning.

Highway LTFT (~60mph):
-7.0% with cruise
Rises to about -4.7 tapping on "+" on cruise
Drops as low as -9.4 holding the decrease speed button on cruise

City LTFT:
Instantly jumps as high as +1.3 with a quick tap on the accelerator
Drops as low as -10.2 while coasting
Averages around -4.7 to -5.5

STFT oscillates by about 1-2% in both directions when warm and a bit more while it was warming up. It once plummeted to about -15% and stayed there for a couple seconds. That was after letting off the gas after about a mile of driving but quickly came back.

I'll have to borrow or buy a fuel pressure gauge to check that. Hopefully I can do so either this weekend or the next. Hopefully it's not the fuel pump- I need that money for school :ugh:
 

mcc

Original poster
Member
Apr 8, 2012
49
I changed my oil last weekend with Pennzoil Ultra 5W-30 and a Fram Xtended Guard XG3675 filter to hold more crud while I'm transitioning to synthetic. I'll probably go with a PureONE on my next change.

The results were immediate. My Envoy doesn't even feel like it's running at idle with the AC off. The engine's smoother and quieter in general. You should've seen the look on dad's face when he realized how dramatic a difference something as simple as an oil change made. :biggrin:

The best part? The issue's nearly gone. My Envoy cranks slightly longer than it used to in the morning but nothing dramatic. It also consistently starts right away after it's been sitting outside for an 8 hour work day.

I'll consider this resolved for now and post back if it becomes a problem again. Thanks!
 

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