No start when cold

Tiny
BCV2017
  • MEMBER
  • 2004 JEEP LIBERTY
  • 3.7L
  • V6
  • 4WD
  • AUTOMATIC
  • 150,000 MILES
If the engine is cold my Jeep will not start with out me giving it gas and then I have to hold the gas until it is warm then it will finally catch. I have already had it to a mechanic and they were pretty puzzled. They said possibly a coolant temperature sensor but that usually pulls a code and their is no codes or engine light on
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Monday, March 20th, 2017 AT 7:03 AM

6 Replies

Tiny
CARADIODOC
  • EXPERT
My guess is the battery was recently disconnected or run dead. This is a common problem, and the clue is the engine runs fine as long as you hold the accelerator pedal down 1/4". Idle speed is too low because the Engine Computer has not relearned "minimum throttle". Until that occurs, the engine will be hard to start unless you hold the pedal down 1/4", you won't get the nice idle flare-up to 1500 rpm at start-up, and it will tend to stall stop signs.

To meet the conditions for the relearn to take place, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals.
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Monday, March 20th, 2017 AT 3:22 PM
Tiny
BCV2017
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I haven't had to jump the battery or nothing but I will give it a try in the morning to see if it works
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Monday, March 20th, 2017 AT 6:10 PM
Tiny
BCV2017
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Well I did that yesterday and it started for the first time on its own in the last 3 weeks not sure if it was just a coincidence or not. Didn't start on the first crank after work but did the second time
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Wednesday, March 22nd, 2017 AT 4:28 PM
Tiny
CARADIODOC
  • EXPERT
The easiest observation is the engine should run up to around 1500 rpm for a few seconds after starting, then come right down to around 800 rpm. Mechanics can tell if minimum throttle has been learned by observing the automatic idle speed motor "steps" the Engine Computer has commanded it to. A scanner is needed for that. Typical for a well-running engine is step 32, (out of 256 steps). If you find it on step "0", minimum throttle hasn't been learned. Try doing the relearn procedure while holding the brake pedal up with your toes. If the brake light switch flickers on due to road vibrations, during the seven-second coast, that will abort the relearn event.

If you find the AIS motor is on a higher step, like 50 or more, the computer is trying to increase engine speed, but without success. That involves a different set of diagnostic procedures related to low engine performance.
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Wednesday, March 22nd, 2017 AT 6:31 PM
Tiny
BCV2017
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Just found out the clamp that hooks the hose on to the gas tank broke off and I was losing gas do u think this could be part of the problem?
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Friday, March 24th, 2017 AT 5:22 PM
Tiny
CARADIODOC
  • EXPERT
Doubtful. There is a means of detecting leaks in the fuel vapor recovery system which would increase emissions. Chrysler does that by pumping the tank and vapor recovery lines up to two pounds of pressure, then they watch to see how long it takes to bleed down. Gas tank filler hoses usually fit pretty tightly, even without a hose clamp, so while there might have been some seepage, I suspect it wasn't bad enough to be detected as a leak. Had that happened, a diagnostic fault code would have been set, and the Check Engine light would have been turned on.

Even when there's a "gross leak detected", which most commonly is due to a loose gas cap, that has nothing to do with the pressurized fuel supply system for the engine. You can have the largest of leaks involving the tank, but pressure is still maintained in the supply line to the engine. It is that pressure that is needed for the injectors to work and for the engine to start and run.
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Friday, March 24th, 2017 AT 5:48 PM

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