Low AFR/Hanging Idle

[Merchant Marine S550]

Recently drove the car from California to Utah(currently here). The car seems to have developed a hanging idle condition after letting off the gas pedal at any rpm. It will hang around 1800-2000 rpm and slowly drop to idle after about 4-8 seconds. The AFR will be around 12.0 and return to 14.0 or 20.0. Performance is down, but it's to be expected with the elevation (5,000'). The only mods on the car are an Airaid CAI and muffler delete. The Airaid still has the restrictor in it.

Any ideas? No CEL. 6500 miles. Got 25.4 MPG on the way out

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[keltymd]

Sounds like a vacuum leak somewhere. Check all the connections on that airaid.

 

[jbailer]

~14.1:1 is normal if you are using gas that has 10% ethanol which most do, it's comparatively hard to find gas with no ethanol. It should be reading that when you are at idle or under very light load driving. It should go to 20:1 when you are driving and let off the gas, that is called fuel cut and is normal. It's also normal for it to go down to about 12:1 when you give it the gas so from your description, I don't see a problem there.

 

[Merchant Marine S550]

~14.1:1 is normal if you are using gas that has 10% ethanol which most do, it's comparatively hard to find gas with no ethanol. It should be reading that when you are at idle or under very light load driving. It should go to 20:1 when you are driving and let off the gas, that is called fuel cut and is normal. It's also normal for it to go down to about 12:1 when you give it the gas so from your description, I don't see a problem there.

It should go to 20:1 almost instantly though, shouldn't it? It takes a relatively long time before it settles out to 20:1.

 

[jbailer]

should be pretty quick, it sounds consistent with the idle not returning to normal, maybe related but I don't think the focus should be on A/F is what I meant.

 

[Merchant Marine S550]

Sounds like a vacuum leak somewhere. Check all the connections on that airaid.

should be pretty quick, it sounds consistent with the idle not returning to normal, maybe related but I don't think the focus should be on A/F is what I meant.

Checked the connections and the clamps on the TB were semi loose. Tightened them all up. Noticed that where the vacuum lines go into the intake elbow via rubber grommets, the grommets are fairly loose and flexible. I doubt they are air tight. Seems like a manufacturing defect almost with it being that loose. I need to get some propane and see if it speeds up when near the connections.

Car will maintain 35mph in 4th with my foot off the pedal.

Does anyone know where I can find a diagram for the vacuum line routing?

 

[Merchant Marine S550]

Pulled the battery terminal overnight in hopes I would see some change. Nothing changed, car still refuses to drop down below 1600 rpm quickly. If I'm just revving the engine in neutral (not with the clutch in), it will drop down quickly and doesn't hang from 1600RPM down to idle.

Not sure if it's related but I got a "SERVICE ADVANCE TRAC" while idling and checking vacuum lines.

Damn this is getting frustrating. Might put the stock air box back on to see if I notice a change.

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