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Vacuum leak. Maybe?

So, after getting my transaxle replaced the shop that did it didnt tighten the exhaust bolts at the downpipe properly so i formed a major exhaust leak. While it was nice to be loud and obnoxious for awhile, the charm is wearing off. But, my idle has progressively gotten worse. When the engine very hot it raises the idle to around 2500 RPMs and while at proper operating tempurates it almost dies or stays at around 400 RPMs which still isnt right. I had an MG that had vacuum leaks and it could cause all of these crazy Idle speeds. I just wanna know if a Vacuum leak is a possibility and which lines i should check or is it something as simple as Spark leads? The plugs are fine and fresh by the way. Everything looks to be fine but i understand that the vacuum lines on these cars are a huge hassle
Old 09-26-2017, 09:18 PM
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Does you idle ever "surge" or "hunt?" My 85.5 exhibited similar symptoms to yours (high idle when hot) - and after a time the idle would also sometimes oscillate rapidly between about 500 and 2000 rpm. A simple test of the Idle Control Valve (ICV - located under the air intake) by disconnecting its lead, indicated no change so implicated the ICV in this problem. I then removed the ICV and rebuilt it - now all is well. A bit of a pain to remove the air intake...but I did not need to disconnect the fuel lines as Clarks recommends (I simply pushed the fuel rail/lines aside). If you do end up going this route - do make sure to replace the intake gaskets!
Old 09-27-2017, 05:00 AM
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Quote:
Originally Posted by OK-944 View Post
Does you idle ever "surge" or "hunt?" My 85.5 exhibited similar symptoms to yours (high idle when hot) - and after a time the idle would also sometimes oscillate rapidly between about 500 and 2000 rpm. A simple test of the Idle Control Valve (ICV - located under the air intake) by disconnecting its lead, indicated no change so implicated the ICV in this problem. I then removed the ICV and rebuilt it - now all is well. A bit of a pain to remove the air intake...but I did not need to disconnect the fuel lines as Clarks recommends (I simply pushed the fuel rail/lines aside). If you do end up going this route - do make sure to replace the intake gaskets!
There is no surging really. Like, it will stay at a very low idle until the engine gets very hot then it will slowly rise up to around 2000 or 2500 RPM and stay there. Even if the engine gets back down to a reasonable tempurature it will still stay at that idle speed regardless

Last edited by Pipemaster; 09-27-2017 at 05:12 AM..
Old 09-27-2017, 05:08 AM
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Check a couple of things. Is the throttle plate hanging up or binding? Is the TPS module loose or adjusted improperly and not reading correctly? Unplug the ICV as suggested. Test the TPS as recommended on Clarks.

Also (on the N/A) you can remove/replace the ICV without removing the intake if you have small hands...
Old 09-27-2017, 01:41 PM
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I'm not clear on this. So immediately when you picked up the car after the transaxle all was well. It idled properly.

Then, the exhaust loosened up from the exhaust manifolds and it was merely loud.
Then, it started idling oddly.
Then you posted on Pelican about the idle.

Currently, the exhaust is not fixed and the idle is not fixed.

Let me know if all the above is correct.

My first suggestion is to take it back to the shop and tell them that the exhaust is loose and the engine is now running incorrectly.

My second suggestion is to fix the exhaust yourself, and then see what you have as to engine operation. And also look around in the area to see what the super heated exhaust might have melted, knocked loose or aged by 10 years in the time you drove it like this.

First though - curious if that sequence is what is going on.
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Old 10-01-2017, 06:10 PM
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Quote:
Originally Posted by IdahoDoug View Post
I'm not clear on this. So immediately when you picked up the car after the transaxle all was well. It idled properly.

Then, the exhaust loosened up from the exhaust manifolds and it was merely loud.
Then, it started idling oddly.
Then you posted on Pelican about the idle.

Currently, the exhaust is not fixed and the idle is not fixed.

Let me know if all the above is correct.

My first suggestion is to take it back to the shop and tell them that the exhaust is loose and the engine is now running incorrectly.

My second suggestion is to fix the exhaust yourself, and then see what you have as to engine operation. And also look around in the area to see what the super heated exhaust might have melted, knocked loose or aged by 10 years in the time you drove it like this.

First though - curious if that sequence is what is going on.
You would be correct in that sequence. I unplugged the ICV from and there was no change in the idle problems so i assume thats where the issue is. If its not broken completely, its on its way out now
Old 10-01-2017, 08:29 PM
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Your ICV might be stuck - try spraying some carb cleaner through it - let it soak, etc. Also check to make sure the throttle plate/linkgage and the throttle position sensor is not loose or hanging up.
Old 10-02-2017, 05:35 AM
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Quote:
Originally Posted by djnolan View Post
Your ICV might be stuck - try spraying some carb cleaner through it - let it soak, etc. Also check to make sure the throttle plate/linkgage and the throttle position sensor is not loose or hanging up.
Ok its not the ICV to my knowledge. I did all of that and there was no change. I hear a very airy sound coming from the top of the engine while its running and sometimes after it cuts off. It just sounds like a really bad vacuum leak. Its also running fairly lean. But yet there are no check engine lights coming on. But its running so lean the engine isnt really combusting anything once i let off the pedal. I mean the car wants to slow down fast and when i push the pedal it stutters back to life. And i mean really stutters and struggles to fire again. As long as i keep my foot on the pedal all is well
Old 10-18-2017, 01:53 PM
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Oh and it shuts off on me while im driving quite often now. Like as soon as i throw it out of gear in the split second before i put my foot on the gas it shuts off
Old 10-18-2017, 02:05 PM
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Sounds like you could have a major vacuum leaks, so check all of the large vacuum lines. A stuck icv would not cause what you are seeing.

First Start at the y-tube venture and make sure it isn't separated or cracked, and follow it up to the brake booster and then in the other direction to the j-boot and throttle body looking for problems.

Second follow the ICV lines from the valve to the j-boot, and then to the intake port on the bottom of the intake manifold and make sure there are no leaks, cracks, separations, etc.

Also look at the air/oil separator lines, the fuel evap lines on the fender wall, and the fuel damper/regulator vacuum lines.

Something has got to be disconnected or broke/cracked somewhere...
Old 10-18-2017, 02:35 PM
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I found vacuum leaks using the "bubble test and the smoke test"
Smoke test question

I used the "thin cigarillos 4 pack at Safeway"

If you see a puff of smoke under the intake replace all the rubber lines under the intake. (one is NLA)
Replace all vacuum hose connections to the tiny tubing. Follow each line end to end.

There is a 2 inch hose under the throttle body that is prone to rot. Can be seen from top on the drivers side.

Buy a "throttle body" reseal kit at ArnnWorx.
ArnnWorx Specialty Tools

It could be the Idle stabilizer but this can be tested after the intake is removed.

Buy 4 intake gaskets----(and a spare set)

Make sure the "J" boot is not rotted.

GL
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Old 10-18-2017, 03:14 PM
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That sucking sound you describe is the O-ring in the ICV failing to seal. Quick test: spray carb cleaner at/on the ICV at idle; if your idle goes up, there's your vac leak. That O-ring can be replaced and your ICV rebuilt, so no need for a new one.
Old 10-20-2017, 07:59 AM
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I checked and i do not see any disconnected vacuum lines. In fact most of them look fairly new. Could it all just be a blown Exhaust manifold gasket from the heat?
Old 10-21-2017, 08:32 PM
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