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how to bypass thermo vacuum switch(think maybe AIS?)...


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11 replies to this topic

#1 scrap487

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Posted 27 March 2006 - 11:15 PM

well.. was going to rip EVERYTHING Off my manifold and carp and plug it, but then I realized that the choke and distributor advance run off of these valves that are controlled by temp. I figure I could get away with hooking the disty advance straight into the manifold, but what about the choke? I dont have what I need to convert to manual choke on hand tonight, but I also want to clean up some of this clutter. if I hook it into the manifold it of course wont run or will run very badly when cold, or if I leave it disconnected it will run when cold but wont run when it gets warm. I suppose if worse comes to worse I could leave it disconnected untill it warms up and the go hook it up as soon as its warm, but that would be a PITA. advice please? I guess my other option is to get some vacuum tubing and get rid of the hardlines on the manifold and hook it up like that system is supposed to untill I get my weber on there but ick... I want to get this done tonight...

Thanks,

Trevor

#2 scrap487

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Posted 28 March 2006 - 12:19 AM

ok after some "professional" detailed examination of the factory service manual, the valves I am talking about are: thermo vacuum switch(I) and thermovacuum switch(II) (TVS 1 and 2 respectively)

TVS 1 is on the intake manifold, has a vacuum hose that goes to the carb(not sure of the function of this, someone please tell me), and a hose that goes to the aircleaner that sucks air in to lean out air/fuel mixture when engine is cold/choke closed. can I just block off both hoses and the port on the carb and call it a day? if its not needed for the carb to work right I think this little peace is gonna go bye-bye. I believe this is the AIS thingy? or is it both of these?

TVS 2 however does more, it has a hose going to the EGR valve, a hose that goes to the distributor and then a hose that goes to the carburator. as I said before, I have no idea what the purpose is of these too hoses going to the carburator so PLEASE TELL ME. they dont go to any diaphram or anything, they just go right into the front of it. I cant find a diagram of these two ports in the FSM. am I safe just to block off the egr port, reroute the vacuum advance to the intake manifold, and block off the hose going to the carb?

PLEASE, need some input before 10pm so my neighbors dont call the cops on me AGAIN!!!!


p.s. early today I kept getting the thermo switches and the thermo vacuum switches mixed up which is part of the reason why I am confused, but i've gotten that mostly sorted out now(I had thought they were the same thing and then I realized one is electrical the other is vacuum)

any electronics I can rip off while i'm at it?

#3 GeneralDisorder

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Posted 28 March 2006 - 12:39 AM

You can eliminate them both - the distributor needs ported vacuum - on the front of your carb. In other words, it gets a rising vacuum signal off-idle, and no vacuum at idle. The hole for this signal is right above the throttle plate.

The other vacuum valve is for the evap system. It will evacuate the carbon cannistor once the sytem reaches operating temp.

Read and UNDERSTAND how each system works on the engine, and this will all make sense. You are wasting your time and ours poking around and asking questions when a little research will save you from scratching your head for hours and begging for help.

Also - I have personally covered each of the systems at length in previous posts - search is your friend as this is all availible for reading at your leisure. Why wait for us to post?

GD

#4 GeneralDisorder

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Posted 28 March 2006 - 12:48 AM

There are usually three vacuum valves, one for EGR as you mentioned. Block the EGR completely, or route it to the other port on the front of the carb - also ported vacuum, but it gets vacuum later than the disty. It's easier to just block it tho.

None of these has anything to do with the AIS, unless the AIS valve is the vacuum operated type (CA emmissions models, and I think some very Carter carb versions). Just disconect it.

GD

#5 scrap487

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Posted 28 March 2006 - 12:50 AM

You can eliminate them both - the distributor needs ported vacuum - on the front of your carb. In other words, it gets a rising vacuum signal off-idle, and no vacuum at idle. The hole for this signal is right above the throttle plate.

The other vacuum valve is for the evap system. It will evacuate the carbon cannistor once the sytem reaches operating temp.

Read and UNDERSTAND how each system works on the engine, and this will all make sense. You are wasting your time and ours poking around and asking questions when a little research will save you from scratching your head for hours and begging for help.

Also - I have personally covered each of the systems at length in previous posts - search is your friend as this is all availible for reading at your leisure. Why wait for us to post?

GD


thanks... makes a little more sense now. I've been on and off searching all day, just for differant questions. the threads I visited were QUITE descriptive but still left a few questions. after doing a whole TON of reading out of the FSM I found that the AIS was mentioned once, near the end of the section about the ECC where as on here its all over the place and I get lost because there arent many threads that make the connection between the AIS and what is actually consists of... i suspected but I've learned not to go tearing crap apart just because its what i *think* it is. I understand where you're coming from, but it doesnt hurt to double check, and my question was a little more specific than your average "how do I get rid of all this emissions crap" thread, trust me i've seen ALLL of your rants about searching and research in ALL of those threads :rolleyes: , I'm grateful you are still willing to help out. I'm not the greatest with factory service manuals but I try my best...

sorry for the inconveniance sometimes I just need to see something drawn out a differant way for it to make sense.

thanks

#6 scrap487

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Posted 28 March 2006 - 12:54 AM

There are usually three vacuum valves, one for EGR as you mentioned. Block the EGR completely, or route it to the other port on the front of the carb - also ported vacuum, but it gets vacuum later than the disty. It's easier to just block it tho.

None of these has anything to do with the AIS, unless the AIS valve is the vacuum operated type (CA emmissions models, and I think some very Carter carb versions). Just disconect it.

GD


crap I just confused myself again... I actually dont know what my car is, might be CA model, which would explain a little why this is more confusing than it should be... so the AIS has nothing to do with those thermovacuum switches I mentioned? the diagram in my book shows that TVS 1 has a hose going to the air cleaner and this the majority of the air induction system because it sucks in fresh air to lean out the mixture during warmup.. thanks

EDIT: ok I just went out and checked, my car IS a CA car, how'd it end up here :(

so I assume its still safe to remove that. route vac advance up to ported vacuum, and block egr.

#7 GeneralDisorder

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Posted 28 March 2006 - 12:59 AM

The AIS is passive - it has NO moving parts.

There are two AIS valves usually - just follow the 1" steel tube up from the bottom of the head right above the exhaust flange and you'll find them. There are a couple plastic silincers and the 1" rubber tubes that hook into the air filter.

You would likely know if you had a CA model. If you have an O2 sensor in your y-pipe where the cat is, then you have the feedback mess. But you probably don't.

GD

#8 GeneralDisorder

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Posted 28 March 2006 - 01:02 AM

Are you SURE it has the computer controlled Hitachi? If so, that's totally different, and you'll thrash you mileage if you mess with a lot of it. You can still remove the systems that are not related to the feedback system, but it takes more in-depth knowledge to sort that stuff out from the computer. The computer will get angry and throw codes at you, then run in "limp" mode with defualt fuel maps till you fix it.

GD

#9 scrap487

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Posted 28 March 2006 - 01:15 AM

ok... well this might throw you through a loop. it has an O2 sensor, and its a CA model and it does have some sort of electrical stuff, BUT its an 81 and as far as I know thats pre-computer. my soob is the runt of the crop... O2 sensor w/ a carb and no computer? I dont have a check engine light anywhere. I also might add I havent had the O2 sensor hooked up the entire time since I lifted it. will it run without a computer?

anyways, I have a weber I'm ready to throw on there as soon as I get an adapter plate so this is pretty much prepping for that if it doesnt work with the hitachi. I will go with a weber eventually but I dont really want to spend $45 for an adapter plate right away.

#10 GeneralDisorder

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Posted 28 March 2006 - 01:26 AM

Yes - it will run without the computer - but not well. You do have a computer - it's under the dash on the drivers side. Your check engine light may be burnt out, or the bulb pulled, or ECU disconnected so you wouldn't see it when you bough it.

The feedback hitachi will run without the computer, but not well, and never correctly. In order to make it run right without all the extra stuff, the carb would have to be swapped out with non-feedback version. The jets and air correctors in the feedback version are not designed to run without the vacuum solenoids that are controlled by the ECU. Just be glad it's not a feedback EA82 - they are worse.

Your strange issues could be related to a bad coolant temp sensor or something. Disconnect the ECU and see if that makes a difference. Also might look into the fuel pump control unit above the hood release latch. It supplies power to the fuel pump... might be bad or getting an incorrect signal from the ECU.

GD

#11 scrap487

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Posted 28 March 2006 - 01:30 AM

Yes - it will run without the computer - but not well. You do have a computer - it's under the dash on the drivers side. Your check engine light may be burnt out, or the bulb pulled, or ECU disconnected so you wouldn't see it when you bough it.

The feedback hitachi will run without the computer, but not well, and never correctly. In order to make it run right without all the extra stuff, the carb would have to be swapped out with non-feedback version. The jets and air correctors in the feedback version are not designed to run without the vacuum solenoids that are controlled by the ECU. Just be glad it's not a feedback EA82 - they are worse.

Your strange issues could be related to a bad coolant temp sensor or something. Disconnect the ECU and see if that makes a difference. Also might look into the fuel pump control unit above the hood release latch. It supplies power to the fuel pump... might be bad or getting an incorrect signal from the ECU.

GD


ok, well I'm gonna quit messing with it then for tonight. I'm buying an adapter plate tomorrow and getting rid of all this junk and getting that webber on there. I wish I had just started trouble shooting my problem like i SHOULD have done :banghead: rather than move on to what i wanted to do. well I'll stop where I'm at, put the carb back on and fire it up before anything else.

#12 scrap487

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Posted 28 March 2006 - 01:30 AM

delete duplicate post.




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