'05 Scion xB hesitates when cold

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  #1  
Old 01-19-09, 06:16 PM
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'05 Scion xB hesitates when cold

Under very gradual to moderate accelleration when cold, or just cool, the engine will hesitate, or cut out momentarily about 3 or 4 seconds after initially opening the throttle, then every second or so, 4 or 5 more times, until the engine speed gets up a bit. Once the engine is warm, no problem. It feels like momentary fuel starvation. In the old days before fuel injection, one could adjust the choke for optimum performance. I've been told modern computerized engines can "self-adjust" as you drive, but not this one. Since the car is out of warranty, the dealer can charge me several hundred dollars for a screwdriver adjustment, so I thought y'all might know if this is a simple adjustment.
 
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  #2  
Old 01-19-09, 06:59 PM
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most likely the temp sensor is not providing proper readings to the computor do you have access to a scan tool?, if so you should be able to check the readings to the computor from totaly cold to warm, it should not show any increases in resistance from the start to warmed up. other possibility is it is time for a injector cleaning, cold engines will react more to slightly off injector spray patterns than warm engines. do you run a good quality fuel? try running some high grade fuel for a couple of tanks and see if the problem goes away.

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  #3  
Old 01-21-09, 06:05 PM
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In fact, I do have a "ScanGuageII" that I installed a year ago, to diagnose a recurring "check engine" light that began coming on at around 50,000 Mi. (I now have 68,000 Mi).
The light would come on and stay on for a day or two, then go off for a day or two, with no driveability problems. To this day, the light continues to cycle on & off every few days. The code is always "P-062" if I recall, and seems to indicate a problem with the intake valve advance or retard actuator failing to activate, but since I have always gotten good gas mileage and good accelleration, I figure the fault is in the sensor itself.
As to the fuel quality, I always use the lowest grade, from various stations. I drive very conservatively, I've never actually "floored" the accellerator since owning it. But I'll try a higher octane for a few tanks to see if any change.
Dirty injectors sounds like the most likely culprit, but you'd think the hesitation would be most pronounced under heavy accelleration; as I say, it's most noticable with the throttle barely cracked when cold.
Oh yeah, one of the four monitoring parameters I keep the Scanguage on is water temp....& it seems to be indicating normally.
 
  #4  
Old 01-21-09, 07:25 PM
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Maybe ask a mechanic and see what they say first.

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  #5  
Old 02-12-09, 05:29 PM
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Started my 3rd tank of mid-grade gas, no difference, same hesitation until water temp reaches about 160F. I also noticed the same hesitation with a more aggressive throttle opening when cold (80F water temp). Altho it doesn't seem to be getting worse from say, a year ago, I wonder if the fuel pump should be checked...?
 
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