[shanef]

So have a boat that is really making me mad here is what I have done. First it is 7.4 merc 2001 mag mpi motor

Surges to 1400 rpms then give it gas goes to 2000 rpms replaced iac,tpi,map new plugs wires distributor and rotor also replaced plenum gaskets checked for codes none found. I now iac has 12 volts on two wires and 4.96 on two hires but iac is not moving. If I take a bolt but it in the iac hole to stop most of the air motor runs great and idles great. But still want to figure this out. Check manafold for vacuum leak also.

[pompeer]

Originally Posted by shanef

So have a boat that is really making me mad here is what I have done. First it is 7.4 merc 2001 mag mpi motor

Surges to 1400 rpms then give it gas goes to 2000 rpms replaced iac,tpi,map new plugs wires distributor and rotor also replaced plenum gaskets checked for codes none found. I now iac has 12 volts on two wires and 4.96 on two hires but iac is not moving. If I take a bolt but it in the iac hole to stop most of the air motor runs great and idles great. But still want to figure this out. Check manafold for vacuum leak also.

My '99 Z260 with same power plant is also surging above idle in a similar manner. Did you find a resolution to this issue?

[mikeyt]

I'm not an expert on this stuff but from one prior experience a few years ago this is my thought: There is an air filter of sorts at the end of the hose that runs from the IAC valve to the throttle body and i think the manual calls it an IAC Muffler. You access it via the throttle body. Basically is an inch square piece of foam like material that can become clogged with carbon. You can try to clean it up but its likely better to simply replace it and that should solve your surge problem.

[shanef]

no not yet but working on it. It stopped running yesterday so it should be easier to find now. lol

does your sound like it is sucking air when it is running?