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Vacuum hoses
Topic Started: Oct 7 2017, 08:32 PM (1,157 Views)
julio3231
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hey guys,

I got my intake and throttle body installed on my 91 Vert, but it turns out the pics I took of the vacuum hoses aren't good enough. I have a hose running from the MAP to the back of the TB, a hose running from the vacuum line mounted to the firewall to the back of the intake manifold. The other two hoses that come off lines mounted to the firewall run to the distributor and the front of the TB. There's a hose running from the timing gear side of the intake manifold to the Distributor also.

Looking at the TB from the front bumper the three vacuum ports are as follows: left side plugged, middle open, and the right side has the hose running to the line on the firewall.

What am I missing?
Edited by julio3231, Oct 7 2017, 08:33 PM.
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geogonfa
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Just curious...is there an emissions decal on the bottom of the hood?...does it have A/C? :type
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julio3231
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Ah you're a genius. It's coated on dirt. Lol
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geogonfa
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:thumb
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julio3231
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So i got it started up and its idling at 3500 rpms.... should I suspect the IAC valve? Before removal of the intake and TB idle sat around 1500 RPM cold and 800 ish warm. I also have only filled the radiator with coolant as i replaced it at the same time as this project.

Any Ideas?
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julio3231
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For some reason I suspect the cooling system needs to be full before the IAC will work correctly. I have a Haynes Manual and its garbage for explaining how systems work.

If I have to fill burp the cooling system at 3500 rpm to get the idle to slow down IM probably going to have to fix the exhaust and hope I don't get a geyser when the thermostat opens I don't think my neighbors will appreciate either.
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suzukitom
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Tom

On the early Metros the fast idle is controlled by a was pellet device that closes off an air bypass port in the throttle body as coolant flow warms up the wax.

Some folks stick a finger over the port to manually block it off to confirm if it is working properly when warmed up.

So you do need coolant in the system and it has to flow hot through the hoses going to the throttle body.

Also check for any air leaks in the hoses as that can also lead to overly fast idle.

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suzukitom
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Tom


A good explanation by Memphis Metro

Posted Image


http://geometroforum.com/single/?p=750453&t=4464045
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julio3231
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I cant hear any hissing sounds. The throttle plate is close to closed and it's surging between ~2600-3000 RPM. Will it take until coolant is in the TB hoses for it to come down to its regular high idle? how does the ISC solenoid valve work? what does it do when it fails?

Additional info: It is a manual transmission and has A/C. i haven't removed any sensors during this project from their mounted positions. The only hoses that have not been replaced are the larger diameter vacuum hoses.
Edited by julio3231, Oct 7 2017, 11:30 PM.
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Me and my metro
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You need to remove the highest small coolant hose on the throttle body to bleed the air.
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MR1 Kingsbury
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Exp. builder/rebuilder

coolant hoses should bleed by theirselves, unless there is a blockage in the TB. More likely with engine surging and very high idle speed is a vacuum leak. recheck all hoses leading to and from the intake manifold and TB. somewhere there is a lot of air not being measured and is leaning out the o2 sensor, tricking the tps, and allowing pcm to deliver more fuel by low vac at map sensor. you can use a mist of carb cleaner around the hoses and listen for a change in engine speed. that will indicate the leaking area. double check the gaskets at TB.
all air involved in fuel mix and engine intake MUST pass through the throttle valve on top of TB

Your 91 does not have ISC (large black box mounted on back of throttle body) you have IAC (idle air control) which, like was mentioned is controlled by coolant temp circulating through throttle body.
Edited by MR1 Kingsbury, Oct 8 2017, 10:20 AM.
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Dystopiate666
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Tree Banger

i think people have problems with the actual TB gasket after it is removed sometimes, spray a heavy load of brake parts or carb cleaner all around the top of the engine to try to make it surge, unless it is a severe vacuum leak, you really need to use a heavy spray for this method to work...another option is to smoke it if you have access to a smoker....
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freegeo
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MR1 Kingsbury
Oct 8 2017, 10:14 AM
coolant hoses should bleed by theirselves, unless there is a blockage in the TB. More likely with engine surging and very high idle speed is a vacuum leak. recheck all hoses leading to and from the intake manifold and TB. somewhere there is a lot of air not being measured and is leaning out the o2 sensor, tricking the tps, and allowing pcm to deliver more fuel by low vac at map sensor. you can use a mist of carb cleaner around the hoses and listen for a change in engine speed. that will indicate the leaking area. double check the gaskets at TB.
all air involved in fuel mix and engine intake MUST pass through the throttle valve on top of TB

Your 91 does not have ISC (large black box mounted on back of throttle body) you have IAC (idle air control) which, like was mentioned is controlled by coolant temp circulating through throttle body.
Quote:
 
you have IAC (idle air control) which, like was mentioned is controlled by coolant temp circulating through throttle body.


I don't have a obd car and it took me a while to get a grasp on the differences of the system.

The picture that suzukitom posted shows the fast idle air valve (the bottom of it). It is in the throttle body and works kinda like a thermostat. When it is cold the valve opens and allows more air in. As the coolant warms up the throttle body and warms the fast idle air valve, the valve slowly closes off, lowering the idle of the car.

The IAC is controlled by the ecm. The IAC's purpose is more for once the engine is warmed up. When a electrical load is applied to the engine.

Found this in the FSM.

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Edited by freegeo, Oct 8 2017, 11:19 AM.
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freegeo
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Did you get the vacuum hose routed according to the emissions sticker? Was the intake gasket the only component removed, you didn't take the throttle body or anything else loose?
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julio3231
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OK so it sounds like I should be chasing just a vacuum leak. Thanks for all the info guys.

The project I was working on was as follows: Replace Radiator, O2 sensor, vacuum hoses and coolant hoses, Intake gasket and TB gasket.

My radiator was missing most of its fins and It had a slight intake manifold leak. I took some time to glass bead blast the intake manifold while it was out and ultrasonic it in soapy water. None of the electrical components got wet and they all were taped off prior to bead blasting though. The throttle body wasn't even in the same room while all of that was going on. I had planned to rebuild the TB, but upon removal I found it to be really clean already, so I just replaced the gasket between the intake manifold and TB during reassembly. As far as I can tell from the diagram on the hood all my vacuum hoses are in the right places.

I'm gonna reset the battery and triple check everything when I get out there to work on it today. Its still too early here on a Sunday to be having my Metro running up RPMs without the muffler attached.
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