Cold Start Issue

Tiny
SBP1960
  • MEMBER
  • 1999 DODGE DAKOTA
  • V8
  • 4WD
  • AUTOMATIC
  • 190,000 MILES
1999 Dodge Dakota Pick Up Truck with an 8 cyl, 5.2 ltr.(318 cid) fuel injected automatic but has some sort of throttle body atop the engine. Having trouble starting when cold. I have a block heater installed, which after 2 hours, or so, of being plugged in, the truck starts fine. Would the "Throttle Position Sensor" cause this hard start? Why does the engine have to be slightly warm in order to start correctly? Is there some sort of choke system within this throttle body that isn't operating properly? Is it in fact a throttle body? The truck runs perfectly fine other than this little dilemma, so I know it's not fuel pressure issue. Need a clear response from someone who knows. Thank you.
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Sunday, March 20th, 2011 AT 6:27 PM

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Tiny
CARADIODOC
  • EXPERT
No choke. All that's in the throttle body is the throttle valve and a controlled air passage around it to adjust idle speed. You shouldn't need a block heater. The first thing to look at is if you get a nice idle flare-up to 1500 rpm for a few seconds after starting. If you do not, chances are the battery was recently disconnected or run dead and the Engine Computer has to relearn "minimum throttle". Until that happens, the computer won't know when it has to be in control of idle speed. The engine should start if you hold the gas pedal down 1/4". If that works, 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 brake or gas pedals. You could also have fuel pressure bleeding off while the engine is off. To identify that, cycle the ignition switch to "run", wait a few seconds, turn it off for a few seconds, turn it on again, then maybe even a third time, then try to start it. If that works, the most likely cause is a leaking injector but the fuel pressure regulator and the check valve in the pump can cause that too. A rare possibility is worn bushings holding the distributor shaft. If the shaft wobbles enough there can be a signal dropout from the camshaft position sensor. When that signal is missing, the Engine Computer won't turn on the automatic shutdown (ASD) relay which powers the injectors, ignition coil, and alternator field. You'll be missing spark when it doesn't start and the injectors won't be firing either. Besides checking for spark you can also measure the voltage on the dark green / orange wire to the ignition coil or any injector. You should see full battery voltage for just one second after turning on the ignition switch, then it must come back during engine cranking.
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Sunday, March 20th, 2011 AT 7:44 PM

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