Bayley

Been having a rather interesting problem these last few outings with a high idle situation on my 454 Mag EFI's with Whipple SC's and the 2100 CFM TB's.

When I first fire up the motors at the ramp, both motors will rev up to about 1400 rpm, then slowly idle back down to a 700 rpm idle. The Port motor idles down a little bit quicker, but the starboard motor will eventually come down. However, as soon as I open the throttle on the starboard engine (simply revving it up is all it takes), the motor will not idle down past about 1200 - 1300 rpm. This is most noticeable when I come off plane into a harbor or channel. I’ve checked the throttle cable many times, and there appears to be plenty of slack in the cable at idle.

Now comes the strange part...
When I pull into the docks, I am forced to grit my teeth and throw the shifter back into gear. It will give me a good "thunk" and the RPM's will drop. What I have to do next, is immediately pull the shifter back into neutral. When I do this, the RPM's will then stay steady at normal idle speed and I can shift in and out of gear all day long (or at least until I open the throttle blades again) without the idle speed going up. However, if I don't quickly pull the shifter back into neutral, the motor will speed up to about 900 - 1000 rpm's while in gear, then back to 1200 - 1300 if I put her back into neutral.

WTF???

I've looked everywhere for vacuum leaks, and the only thing I found was that the starboard motor didn't have a PCV valve (instead, just a plastic 90 degree elbow into the valve cover). I installed a PCV for $hit's and grins, but it didn't make a bit of difference. Next thing I did, was start up the starboard motor and disconnected the IAC when the engine was idling normally. Nope, motor would rev back up as soon as I opened the throttle body even with the IAC disconnected.

The only thing I can think of, is that the throttle blades themselves are not completely closing. When I load down the engine (putting into gear), the vacuum created from the load could possibly be pulling the blades fully closed. This might explain why if I left the load on the engine, the high initial vacuum load would eventually re-open the blades on their own. Maybe I'm just smacking crack instead.

I've noticed that the Throttle Body's (made by Whipple) have adjustments for the stops on both the primary and secondary blades. Before I go tearing into the TB's and adjusting these stops (not the easiest to get to), is there anything that I might be missing?

Any advice appreciated.

Thanks
-Bayley

obnoxus

Take a look at the plug going to the thermostat gooseneck. I had a wire pull out just enough to break contact, but not be visably noticable without pulling the connector off. The guage worked fine, but had a high idle that would eventually come down but like you said it took a while. Hope this helps.

blown formula

This sounds similar to a high idle speed condition I had BEFORE meltdown..... A couple of questions first:
Do you have Aeromotive fuel pumps? (red ones?)
Does the engine ever die from the high idle speed when put in gear?

I would check for a clogged injector filter screen on the injectors. Its easy to do.

Aeromotive fuel pumps manufaqctured before May of 2002 can/will desolve the epoxy holding the magnets in the motor. That epoxy WILL go to the injector screens and cause it to lean out as they plug up......this is what melted my piston,
I hope you find it, cause it sure sounds like "lean" is the cause.

Bayley

Thanks for the good advice guys,

I'll look into the T-stat wiring. I've had pinched wires befire that have caused me all sorts of headaches. You never know.

Formula,
I'm still using the OEM Merc pump with a small aux. pump that Whipple provides with their kit. Been thinking about swapping over to one large (Aero) pump and removing the extra injectors, but have yet to do so. I'm 99% sure that this is not due to a lean condition. If anything, the plugs look a little rich and these is a good (equal) amount of soot on the transom from both motors. It is a thought however, and worth looking into.

Thanks again
-Bayley

Whipple Charged

Bayley,

This has nothing to do with a close to burning up problem. Either they are set so the the blades are allowing to much air to enter the engine and or the TPS voltage is too high. First, measure the TPS sensor with the throttle all the way closed, the blue wire is the signal wire, should be near .55-60 volts, if higher, simply loosen it's mount and twist until the volts come near .55. If the voltage is fine, then adjust the throttle linkage stop so the linkage will allow the blades to close more, it needs very small adjustments, the secondary is the easiest to work on. All you will be doing is lowering it's stop so make sure it's not already not touching.

Thanks,
Dustin

H2Xmark

hows that for customer service, I was getting ready to tell him the same thing Dustin!

Bayley

Update:

Dustin, thanks for the advice. I did check the TPS voltage and measured 560 mV. This was actually a little surprising to me, since I expected the voltage to be a little high if the stop was holding the primary blade open ever so slightly. What I found instead, was that the SECONDARY stop nut had backed out sligthly causing the secondary to be slightly opened. I tightened this bolt back down and verified that they were closed. It worked OK, I still had the motors rev up on me once the entire weekend, but it went back down fairly quickly and wasn't as bad as it was before. I need to check the primary stop next.

Thanks again everyone.

-Bayley