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sprinkles08
sprinkles08, ASE Certified Technician
Category: Jeep
Satisfied Customers: 21604
Experience:  Chrysler/Dodge/Jeep Master Certified, ASE Master and Advanced Certified, Trans and Hybrid Specialist
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Jeep wrangler: i have a 1999 jeep wrangler with a 4.0 motor.

Customer Question

i have a 1999 jeep wrangler with a 4.0 motor. it had an exhaust leak so i pulled the intake and exhaust manifold off and replaced the gasket and the donut gasket for the exhaust pipe. when i was putting the pipe back on i broke the oxygen sensor so i replace it as well. now when you try to start the engine it revs to the point that you cant stop it, like 6,ooo rpm. i thought it had a vacume leak so i replaced the exhaust, intake gasket again making sure to tighten the bolt in torque sequence. still rev up to 6,000 on startup. help me please.
Submitted: 1 year ago.
Category: Jeep
Expert:  Eric replied 1 year ago.
HI,
Most common cause of this after this type of repair is either accelerator cable binding, throttle body throat plate actuator binding or the throttle body throat plate stuck wide open and not able to close
You need to carefully go thru each of these to find where the bindage is and correct.
Customer: replied 1 year ago.
none of the solutions helped. nothing stuck in the throttle body, no binding of the cables. answers didn't help.
Customer: replied 1 year ago.
the answers didn't help.
Expert:  sprinkles08 replied 1 year ago.
Hello and welcome to JustAnswer!
If the throttle blade is closed then you have a vacuum leak. It could be a hose that was left off or damaged but it takes a larger leak than even the brake booster hose to cause engine speed to go that high.
What is happening is the intake is catching on the dowel pins on the bottom side when you're tightening it. This leaves a gap on the bottom and the bolts may feel normal when you're tightening it, but the bottom of the intake isn't touching the gasket and that's where the vacuum leak is. Loosen the intake bolts and push the bottom of the intake to the head. The lower bolts will need to be tightened by hand while the intake is held against the head. Then the upper bolts can be tightened by hand, and then you can go around and torque them.