View Full Version : New Engine redlining when on startup

11-20-2007, 10:14 AM
I just finished the installation of a new 4.0 motor into my 93 LWB with 190K miles. When I start the motor the tach jumps to over 4K rpms with the engine roaring. As you can imagine, I am very nervous about this situation! I am not in a position to simply start unplugging things or making adjustments with the engine running as I fear it would fail shortly. I assume it is something mechanical, either the intake/flap or the thottle cable has a knink in it somewhere. There are a couple bends in the cable. The only other thing that I can think of is that I may have finally broke the distributor trying to remove the rotor as the shaft popped up. I have a replacemnt on order. The other thing is the stud on the back of the driver side head got cross threaded during the attempt to attacch the two ground wires/straps and I have now grounded those wires with a battery strap that is attached to a known good ground.
Anyway, I am hoping that any of you have some suggestions on what this might be that is causing a great deal of concern.


Mark Douglas

11-20-2007, 06:53 PM
seems you may have the answer, check that the throtle wire works freely, if kinked intall a new one, pull the intake hose and check for the buterfly to return to normal shut position, also check the idle control valve for carbon and proper connection, sometimes the coolant temp sensor would make the ecu think the engine is cold and send a signal to rev up.
all that can be checked with out having to run the engine.
check your timing too.