Got her running..., 4000 RPM idle speed!!!! Options

[bpetry]

OK, so I just got my '72 1.7 EFI running for the first time. Replaced all the vacuum and fuel lines and I thought everything was hooked up corectly per the pelican tech diagrams but after she fires up she idles for a few seconds and then zips right up to 4000 RPM (with no muffler I'm sure the neighbors loved that!). The throttle plate is almost all the way closed so it must be sucking air from somewhere else. I pinched off the big hose that goes from the plenum up near the oil fill and that seemed to slow it down a little, but I don't like letting it rev that high, especially when it hasn't been run in so long so I shut her off and figured I'd come in and ask the experts, any ideas?

Regards,
Brian Petry,
Springboro, OH

[jimkelly]

first get a muffler on it : )

maybe disconnect cold start valve?

turn ecu knob counter clockwise all the way?

check to see that intake plenum has all vents capped or connected.

jim

[brp986s]

I disagree with altering the ecu mixture and cold start valve. A rich mixture won't cause a 4000rpm idle. There is obviuosly way too much air going in.

If you take off the air cleaner and slowly block off the intake, does it slow or stall? If no, the air is coming from somewhere else. You say the throttle is "almost all the way closed". Not sure I know what that means.

[McMark]

The throttle would have to be significantly open to bring it up to 4000 rpm. You have a hose that's not correctly hooked up. Trace them out or take a few pictures and post them.

[nola914]

There's a bunch of possibilities. Sounds like too much air Re-check all of your hoses and connections for leaks. I use clamps on EVERYTHING, and I test all of the hoses for leaks from cracks with the old "mouth pressure" test.

The throttle plate should be completely closed, and the air intake controlled by other mechanisms.

Throttle Switch. Check for 22 clicks as the plate opens and check if the open and closed contacts are working. Also check the idle speed adjustment on the switch.

Aux Air Valve not closing properly, or the hose is leaking.

Fuel Pressure. Too much will make it run very rich. Shd be 29.5 psi.

The idle air by pass screw. Maybe open too far.

Manifold Pressure Sensor. Could be defective. Also check that the hose is not leaking.

Personally, I wouldn't change the ECU knob settings until all else has been checked.

[Dave_Darling]

You have a large air leak. Most likely you have a hose going straight from something "upstream" of the throttle (like the air cleaner, or the rubber hose from the air cleaner to the throttle), to "downstream" of the throttle body (like the manifold). There should never be any hoses that go directly from the one to the other, without having some "component" in the middle.

--DD

[BiG bOgGs]

Just recently I got my engine fired again, also after all new hoses, and was idling around 2500 rpm. I hadn't replaced the manifold to intake runner connectors, and that is where I found my air leak. After 8 hose clamps, she dropped down to a smooth idle just below the 1000 mark.


Check for air leaks.

[bpetry]

Thanks for all the replies. I've got a bunch of stuff to look for. I know the AAV hose is cracked and meant to address that before I got too far into it. Can I just plug it for now? Also I just noticed, the PCV line wasn't plugged into the PCV, so between those things that is probably alot of it right there. I'm used to working on carbureted vehicles that won't idle at all when there's a vacuum leak, not the opposite!

[army dude]

Its not supposed to idle that high?

Ian

[swl]

I agree with all the air leak guys. It is going to be something big. You know your hoses are good - that's a great start. Has anything popped off? I keep pulling off the line going from the aar to the decel valve - thats enough to push it up close to 4000rpm. That crack in the AAR hose may also be big enough to do be contributing if it is the one on the manifold side. I suppose you could plug it to check if that is the source of the air leak. Might be harder to start but it shouldn't do any harm. Better let someone else confirm that though 'cause I'm flying by the seat of pants on that one.

[bpetry]

Yep it was the AAR hose to the intake. I plugged it and its idling fine now! Its really running great for as long as it was in mothballs (12 years). Thanks for all the help! (I'm sure I'll be needing a lot more before I'm done.

[ConeDodger]

Mark asked me to take a picture of it and I will get to it one of these days... I had a 2.0 intake plenum that I powdercoated and subsequently sold to Jeeper John. When I delivered it to Mark to put on Johns 2056 build I noticed as soon as I had it in the light that it was full of pin holes. These are vacuum leaks. Vacuum leaks are NOT ALLOWED with fuel injection. Somehow, you have a vacuum leak.

I gave John his money back.

[McMark]

Bring it with you Saturday Rob. We'll show it off and I'll take the pictures myself. (IMG:style_emoticons/default/wink.gif)