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Rpm spikes 30 seconds after starting truck...

  #1  
Old 01-25-2019
AzRangerLife's Avatar
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Rpm spikes 30 seconds after starting truck...

Ok, so, what I've got going on is.... When I start my truck, instead of the rpms dropping like a normal vehicle after a minuremor two, mine after 30 seconds (i counted over and over) my Rpms spike to around 2000 and stay there. I've checked for vacuum leaks and found none. Was gonna try wanting the iac / throttle body next. Anyone had this issue? It spikes to 2000rpm in park, and in gear stopped at a light, idles around 15-1800 rpm...
 
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Old 01-25-2019
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While running in park or neutral, unplug the IAC. Rpms should drop to around 500 or the engine may die. Either means the IAC is working.
 
  #3  
Old 01-26-2019
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Did that, no change. I swapped the iac with a new one, changed, but still does it intermittently. The change is that it did it constant before. Now it will be fine, but then every few miles it will kick up again for awhile, then suddenly drop again. There was allot of carbon build up though, so I'm thinking i need to clean it up on the intake side.
 
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Old 01-26-2019
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Originally Posted by AzRangerLife View Post
I've checked for vacuum leaks and found none. Was gonna try wanting the iac / throttle body next. Anyone had this issue? It spikes to 2000rpm in park, and in gear stopped at a light, idles around 15-1800 rpm...
Originally Posted by Fordzilla80 View Post
While running in park or neutral, unplug the IAC. Rpms should drop to around 500 or the engine may die. Either means the IAC is working.
Originally Posted by AzRangerLife View Post
Did that, no change.
Check again for vacuum leaks because you have one, when you unplugged the IAC your RPM should have dropped.
 
  #5  
Old 01-28-2019
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Ditto on the leaks. Then clean the maf. Finally run by a parts shop and ask if they can scan it for pending codes and while they’re in there ask if they can see the fuel trims...
 
  #6  
Old 01-30-2019
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I first suspect vacuum leak. Secondly you might consider replacing the ECT (it falsely tells the ECU its very cold and the IAC gets a command to raise idle)
 
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