Engine revs to 4500 RPMs on start-up and stays in open loop

Rebel Warchief

Rebel Warchief

New Member
Joined
Nov 8, 2019
Messages
3
Location
Gurley, Alabama
- New Cylinder head and Valves and Gasket
- New Thermostat
- New O2 Sensors
- New Intake Manifold
- New Exhaust Headers
- New Ignition Coil
- New Spark Plugs
- New Manifold Cover with Gasket

Engine upon startup is revving to 4500 RPMs constant and staying on an Open Fuel Loop... What could be the problems..?

Thanks in advance
 
1RAD said:
Maybe, but 4500 seems a bit fast
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A leak where the intake manifold seats to the head can admit as much or even more air than the throttle body can when you step on the gas pedal. So of course it can cause those rpms, it can easily cause the engine to rev even faster than 4500 rpms.

The bottom line is you did not get the intake manifold properly seated against the head and no you can't just tighten the bolts to get it sealed. You're going to have to essentially re-do that part of the installation and make sure the intake manifold gets properly positioned over the small positioning studs. This is a common problem caused by rushing that part of the job.
 
Jerry Bransford said:
A leak where the intake manifold seats to the head can admit as much or even more air than the throttle body can when you step on the gas pedal. So of course it can cause those rpms, it can easily cause the engine to rev even faster than 4500 rpms.

The bottom line is you did not get the intake manifold properly seated against the head and no you can't just tighten the bolts to get it sealed. You're going to have to essentially re-do that part of the installation and make sure the intake manifold gets properly positioned over the small positioning studs. This is a common problem caused by rushing that part of the job.
Click to expand...

I completely understand and agree on the additional air, but don’t recall ever seeing an engine sustainably run that fast without fuel or other indicators of a major vacuum leak.
 
1RAD said:
I completely understand and agree on the additional air, but don’t recall ever seeing an engine sustainably run that fast without fuel or other indicators of a major vacuum leak.
Click to expand...
The intake not seated correctly on the locating pins is a major vacuum leak.
 
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