High idle speed

I changed from a Bird Injector (hat nozzles only and square barrle valve) to a Gerardot Mag Injector (K barrel valve, hat and port nozzles) and cannot get the engine to idle under 3000 rpm. The only way to get it to idle at 1500 rpm is to increase the leak down to approximately 90% which made the engine drop cyclinders at idle.
I had the Bird set at 75% leak and 5thou air gap on the butterflys and idled at 1500rpm. Set the Gerardot the same and the engine idles at 3000rpm. I closed the butterflys as far as I could get them to go and made little change. Has anybody got any ideas on how to get the idle speed down without having to lek the barrel valve to 90%?

 

I am far from an expert, however any time our alcohol car idle incresses it is due to a lean condition. Maybe your new hat surface/nossle area is to small with your new fuel system. just a thought, based on information i am just throwing a dart at the tuning board

Clarky

 

Air leak somewhere?

 

Is there aerated nozzles in the hat and non-aerated nozzles in the manifold.

 

I had the same high-idle problem, around 3500, and putting some sealant between the hat and restraint-plate, and, restraint-plate and blower brought the idle down to around 1800.

Listen to Mike, he knows what he talks about.

 

One other thing, the square barrel valve gives the injectors more pressure than the k one.

 

this may sound silly but... Did you try to back off the stops and seat the butterflies in their bores?
I know doing this with stack injection makes a huge difference and must be done every time you reinstall it and i had a similar problem with a aquadstar injector. you could have one butterfly hanging slightly open.

 

As some of the other folks have indicated be sure you have a good seal between injector body and blower. Also the new injector butterflies may have more sq. inches of area. If so setting the air gap the same as before will result in a higher idle. If you canot control the idle rpm by closing the air gap in the butterflies and you have airreated manifold nozzles or hat nozzles you can just put a piece of duct tape over the hole in nozzle as a quick fix or check. If all other things are the same in the engine as before you installed the new injector you should be able to get the idle where you want it by leaking the bv the same and being sure you have no additional air leaks. If you changed manifolds you should check it for leaks also. Of course the idle is greatly effected by the DA. If the air is better it will idle faster. When the air is great I have to shut the butterflies in my Gerdot upright to .002 and have all idle plugs in to get back down to my required idle speed.

 

IF i understood well you put on a bigger size injector. Also now you have ports nozzles so in fact you now have less fuel at idle due to the port nozzles being on a check valve.

What I have done in the past is to get the idle check a couple pounds HIGHER at a time and keep the leak down the same. More pressure will put more fuel into the engine at idle but it is less change than leak down.. It is not uncommon to have a 9 psi- 13 psi idle press.

 

A buddy of mine with a new car, engine etc, got to the track for its first fire up but he didnt like the color of the butterflies, and he changed
them (different color) he could not get his idle down,.upon inspecting
the butterflies they were ok at the bottom, but had huge gaps at the top..
we put the old butterflies back in it,..fixed.

 

Vic....
must have had them in backwards....

 

leak check

take the air cleaner off if you have one. start the engine and put something "solid" over the manifold, piece of carpet or something similar, not a plastic bag that will suck in. Did the motor keep running? if so, you have a leak. Use some great stuff or silicone and seal it.

If the motor quits start checking the things above, do you have hat nozzle bodies in the port holes?

quick review on how i do it.
check your butterflies make sure none are bent, try re-setting them. Loosen up all the butterflies on one shaft, slide them one direction while not completely closed. put 2 marks on the butterflies at the screw points on the tight side of the shaft with a sharpie razor point. Now slide the shaft all the way one direction, put a mark on with a sharpie razer point. Slide the shaft all the way the other put a mark on the other end, now center the shafts. close the butterflies tap the butterflies shut lightly with a screw driver handle. Look at the marks you put on the butterflies to be sure the butterflies are square, the marks are equal distance from the shaft. Tighten the screws in the butterfly with a small amount of loctite on them. Now set your butterflies with a feeler gauge.
Do the same with the second shaft.

 

Often a stuck EGR valve or IAC valve will cause this kind of problem, have you tried a can of BG44K in the fuel?

Pat Goss