Hanging Idle and "Cruise Control"
Launching!
Joined: Dec 2012
Posts: 206
Likes: 10
From: California Central Valley
No problem man. Anything I can do to help any of my fellow LS engine owners. My mechanic called me over and showed me the smoke test so I could see the leaks for myself after he found them. He removed my lid/MAF. Then he attached a hose into the air bellow from where the MAF connects to the throttle body. On the other end of this hose was an air compressor on a low setting that was pumping in air that was filled with some kind of white smoke. So he turned the air compressor on and opened up the blade of the throttle body so after a minute as the intake manifold filled up with this white smoke, the pressure inside the intake started to rise and it was looking for a way to escape. In result, it starts seeping out of all of the places where you have a vacuum leak. So instead of spraying cleaner everywhere and trying to find the leak, you just wait a minute with the smoke test and you can actually see with your own eyes where the smoke is leaking out of. It does not damage anything either since the compressor is on low and there is openings where the compressor's hose attaches to so the pressure does not get too great.
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Joined: Apr 2007
Posts: 867
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From: Montgomery (Lake Conroe,) TX north of Houston
Thank you so much for that description of the smoke test. I think that I could rig something up like that to troubleshoot my car. I hate spraying all of that carb cleaner on everything since it's so harsh.
My car is burning more gas than normal so I know that something is wrong (vacuum leak?) causing the high idle. Gotta find the problem.
My car is burning more gas than normal so I know that something is wrong (vacuum leak?) causing the high idle. Gotta find the problem.
Launching!
Joined: Dec 2012
Posts: 206
Likes: 10
From: California Central Valley
You would think that some of it would go through there. Some probably did. Maybe the compressed air was warm so it rose to all of the openings from the top first? One thing I did not note is that my mechanic told me I had to leave my car there overnight because the smoke test works better "when it's cold". I don't know if by "it" he meant the engine or the outside environment. The mechanic I went to is not too far away from where I live so next time I'm around there and he does not look too busy I will ask him the details about that. It was pretty cool being able to visually see where all of my vacuum leaks were though!
Danny: I do not know if you have checked that hose that is between your PCV valve and your intake manifold but I would really check it out if I were you as I found it is very very common for that to go. Also my actual hose there was in fine shape but it just didn't have a very good seal to the male ends of each side. So I put the hose clamps on each side. You might just wanna give that a try because I have been finding that it is a very common place for vacuum leaks in our cars.
Danny: I do not know if you have checked that hose that is between your PCV valve and your intake manifold but I would really check it out if I were you as I found it is very very common for that to go. Also my actual hose there was in fine shape but it just didn't have a very good seal to the male ends of each side. So I put the hose clamps on each side. You might just wanna give that a try because I have been finding that it is a very common place for vacuum leaks in our cars.
I read some place about the smoke test being done. it said in the article that they "capped" the exhaust at the tailpipes.
Considering you could do that with just a pipe cap made from pvc (plumbing store) and a piece of boot from like an intake kit, it should not be too hard to figure out how to do.
Thinking about it, a really low buck version would be to light a cigarette down the intake tube away from the throttle body, leaving the tube pointing up. Smoke rises up the tube and into the intake looking for a way out, regulate the pressure of an air gun down to say 10 psi and make a cap setup for the intake with a small port to allow you to pressurize the tube. Couple short squirts up the tube forces the smoke filled intake air out any leaking spots. Have one person giving the short spurts, and the other (owner having to deal with the hassles) looks around the engine bay for where it could be leaking.
Considering you could do that with just a pipe cap made from pvc (plumbing store) and a piece of boot from like an intake kit, it should not be too hard to figure out how to do.
Thinking about it, a really low buck version would be to light a cigarette down the intake tube away from the throttle body, leaving the tube pointing up. Smoke rises up the tube and into the intake looking for a way out, regulate the pressure of an air gun down to say 10 psi and make a cap setup for the intake with a small port to allow you to pressurize the tube. Couple short squirts up the tube forces the smoke filled intake air out any leaking spots. Have one person giving the short spurts, and the other (owner having to deal with the hassles) looks around the engine bay for where it could be leaking.
TECH Resident
Joined: Apr 2007
Posts: 867
Likes: 218
From: Montgomery (Lake Conroe,) TX north of Houston
You would think that some of it would go through there. Some probably did. Maybe the compressed air was warm so it rose to all of the openings from the top first? One thing I did not note is that my mechanic told me I had to leave my car there overnight because the smoke test works better "when it's cold". I don't know if by "it" he meant the engine or the outside environment. The mechanic I went to is not too far away from where I live so next time I'm around there and he does not look too busy I will ask him the details about that. It was pretty cool being able to visually see where all of my vacuum leaks were though!
Danny: I do not know if you have checked that hose that is between your PCV valve and your intake manifold but I would really check it out if I were you as I found it is very very common for that to go. Also my actual hose there was in fine shape but it just didn't have a very good seal to the male ends of each side. So I put the hose clamps on each side. You might just wanna give that a try because I have been finding that it is a very common place for vacuum leaks in our cars.
Danny: I do not know if you have checked that hose that is between your PCV valve and your intake manifold but I would really check it out if I were you as I found it is very very common for that to go. Also my actual hose there was in fine shape but it just didn't have a very good seal to the male ends of each side. So I put the hose clamps on each side. You might just wanna give that a try because I have been finding that it is a very common place for vacuum leaks in our cars.
. I don't even want to drive my car anymore and I find myself avoiding it and driving one of my other old cars. I'm sooooooooo 
!I tried looking at that PVC hose but it's completely encased in some type of outer insulating, foam rubber type material. Not only that, it seems to be secured down to the intake manifold and there seems to be a bunch of fragile plastic clips and what not all near that hose making it impossible for me to see anything but the very end at the front of the engine. I did notice that it seemed to be loose on the PCV valve so I also clamped it.
I've also had screwy temp gauge readings so I purchased new OEM parts; engine coolant temp and air intake temp sensors and installed them. None of this has helped and I've still got high idle speeds.
I know I'm going to have to fight that complete PVC hose out of there but I just know that I'm going to destroy lots of little things and probably make even more trouble for myself.
Well I had the same problem after getting my new motor tuned, turned out to be the TPS. Seems they can just start to go bad and cause all sorts of funny issues WITHOUT throwing a code. They can be tested, but new only cost around $30. Good luck!
Another way to find out if it is a vacuum leak is to get it smog tested and see if your putting out high HC.
Another way to find out if it is a vacuum leak is to get it smog tested and see if your putting out high HC.
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Verdad Gallardo TECH Resident
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From: Montgomery (Lake Conroe,) TX north of Houston
Anthony thank you for your reply.
I'll keep that TPS in mind but the smog test thing is a not an option where I live.
I keep thinking that my idle speed problems are temperature related.
1. On cold start up, the engine idles higher than it used to and stays high until the engine gets nice and warm.
2. Most of my trips are very short, less than 3-4 miles one way. Often the engine never reaches full operating temperature and my rolling idle speed with the clutch pedal depressed is about 1000rpm. This is quite a bit higher than it used to be! Once I come to a full stop, it falls to about 750-800.
3. If I drive further (10 miles) and the engine is up to temp, I notice that my idle speed problems disappear. It seems to idle like it did when new with a rolling idle speed of about 750-800 with the clutch pedal depressed (neutral.) When I come to a complete stop, it falls another little bit to about 700rpm.
Like I said, this all leads me to believe that it's temperature related so I replaced two of the temperature sensors (ECT and IAT) and all it did was lighten my wallet. I know deep down inside that the problem is most likely what Fourth-Gen Man says; it's the dreaded, difficult to find vacuum leak !
I'll keep that TPS in mind but the smog test thing is a not an option where I live.
I keep thinking that my idle speed problems are temperature related.
1. On cold start up, the engine idles higher than it used to and stays high until the engine gets nice and warm.
2. Most of my trips are very short, less than 3-4 miles one way. Often the engine never reaches full operating temperature and my rolling idle speed with the clutch pedal depressed is about 1000rpm. This is quite a bit higher than it used to be! Once I come to a full stop, it falls to about 750-800.
3. If I drive further (10 miles) and the engine is up to temp, I notice that my idle speed problems disappear. It seems to idle like it did when new with a rolling idle speed of about 750-800 with the clutch pedal depressed (neutral.) When I come to a complete stop, it falls another little bit to about 700rpm.
Like I said, this all leads me to believe that it's temperature related so I replaced two of the temperature sensors (ECT and IAT) and all it did was lighten my wallet. I know deep down inside that the problem is most likely what Fourth-Gen Man says; it's the dreaded, difficult to find vacuum leak
! Launching!
Joined: Dec 2012
Posts: 206
Likes: 10
From: California Central Valley
Anthony thank you for your reply.
I'll keep that TPS in mind but the smog test thing is a not an option where I live.
I keep thinking that my idle speed problems are temperature related.
1. On cold start up, the engine idles higher than it used to and stays high until the engine gets nice and warm.
2. Most of my trips are very short, less than 3-4 miles one way. Often the engine never reaches full operating temperature and my rolling idle speed with the clutch pedal depressed is about 1000rpm. This is quite a bit higher than it used to be! Once I come to a full stop, it falls to about 750-800.
3. If I drive further (10 miles) and the engine is up to temp, I notice that my idle speed problems disappear. It seems to idle like it did when new with a rolling idle speed of about 750-800 with the clutch pedal depressed (neutral.) When I come to a complete stop, it falls another little bit to about 700rpm.
Like I said, this all leads me to believe that it's temperature related so I replaced two of the temperature sensors (ECT and IAT) and all it did was lighten my wallet. I know deep down inside that the problem is most likely what Fourth-Gen Man says; it's the dreaded, difficult to find vacuum leak !
I'll keep that TPS in mind but the smog test thing is a not an option where I live.
I keep thinking that my idle speed problems are temperature related.
1. On cold start up, the engine idles higher than it used to and stays high until the engine gets nice and warm.
2. Most of my trips are very short, less than 3-4 miles one way. Often the engine never reaches full operating temperature and my rolling idle speed with the clutch pedal depressed is about 1000rpm. This is quite a bit higher than it used to be! Once I come to a full stop, it falls to about 750-800.
3. If I drive further (10 miles) and the engine is up to temp, I notice that my idle speed problems disappear. It seems to idle like it did when new with a rolling idle speed of about 750-800 with the clutch pedal depressed (neutral.) When I come to a complete stop, it falls another little bit to about 700rpm.
Like I said, this all leads me to believe that it's temperature related so I replaced two of the temperature sensors (ECT and IAT) and all it did was lighten my wallet. I know deep down inside that the problem is most likely what Fourth-Gen Man says; it's the dreaded, difficult to find vacuum leak
!I have found a couple threads of people claiming this is their only issue and it solves the problem. Hopefully it's the same for you.
TECH Resident
Joined: Apr 2007
Posts: 867
Likes: 218
From: Montgomery (Lake Conroe,) TX north of Houston
Fourth-Gen, here is a pic of my PCV (at least I think this is the PCV):
I think that is the PCV because this is what I found on Install University:
This Install University picture came from: http://www.installuniversity.com/ls1...alve-swap.html
Here is a picture of me pointing to the soft rubber insulation covering the PCV hose:
And here I am pointing to the hard plastic PCV hose inside the insulation:
That hose continues aft along the intake manifold and then way up under the cowl, it appears to wrap around toward the driver's side. I looks almost impossible to get to the aft part of that hose back there. I'm going to have to figure out where it goes because I need to remove it to determine if there are any leaks in it.
I call it a hose but it is more of a hard plastic pipe. I'm hoping that I can get it out and that it has a hole in it somewhere. That would be the "smoking gun" that I'm looking for.
FWIW, my car is a 2002 WS6 and the Install University car is a 1999 Z28.
I think that is the PCV because this is what I found on Install University:
This Install University picture came from: http://www.installuniversity.com/ls1...alve-swap.html
Here is a picture of me pointing to the soft rubber insulation covering the PCV hose:
And here I am pointing to the hard plastic PCV hose inside the insulation:
That hose continues aft along the intake manifold and then way up under the cowl, it appears to wrap around toward the driver's side. I looks almost impossible to get to the aft part of that hose back there. I'm going to have to figure out where it goes because I need to remove it to determine if there are any leaks in it.
I call it a hose but it is more of a hard plastic pipe. I'm hoping that I can get it out and that it has a hole in it somewhere. That would be the "smoking gun" that I'm looking for.
FWIW, my car is a 2002 WS6 and the Install University car is a 1999 Z28.
Launching!
Joined: Dec 2012
Posts: 206
Likes: 10
From: California Central Valley
Fourth-Gen, here is a pic of my PCV (at least I think this is the PCV):
I think that is the PCV because this is what I found on Install University:
This Install University picture came from: http://www.installuniversity.com/ls1...alve-swap.html
Here is a picture of me pointing to the soft rubber insulation covering the PCV hose:
And here I am pointing to the hard plastic PCV hose inside the insulation:
That hose continues aft along the intake manifold and then way up under the cowl, it appears to wrap around toward the driver's side. I looks almost impossible to get to the aft part of that hose back there. I'm going to have to figure out where it goes because I need to remove it to determine if there are any leaks in it.
I call it a hose but it is more of a hard plastic pipe. I'm hoping that I can get it out and that it has a hole in it somewhere. That would be the "smoking gun" that I'm looking for.
FWIW, my car is a 2002 WS6 and the Install University car is a 1999 Z28.
I think that is the PCV because this is what I found on Install University:
This Install University picture came from: http://www.installuniversity.com/ls1...alve-swap.html
Here is a picture of me pointing to the soft rubber insulation covering the PCV hose:
And here I am pointing to the hard plastic PCV hose inside the insulation:
That hose continues aft along the intake manifold and then way up under the cowl, it appears to wrap around toward the driver's side. I looks almost impossible to get to the aft part of that hose back there. I'm going to have to figure out where it goes because I need to remove it to determine if there are any leaks in it.
I call it a hose but it is more of a hard plastic pipe. I'm hoping that I can get it out and that it has a hole in it somewhere. That would be the "smoking gun" that I'm looking for.
FWIW, my car is a 2002 WS6 and the Install University car is a 1999 Z28.
I did a smoke test on mine with the rocker arms off so all valves were closed. Used a tire pump that had both a in and out line for blowing up rafts and hooked it draw from a hookah.
It pushes 6 psi and I had no looks so I would say now I can be certain mine is not vacuum related.
It pushes 6 psi and I had no looks so I would say now I can be certain mine is not vacuum related.
I did a smoke test on mine with the rocker arms off so all valves were closed. Used a tire pump that had both a in and out line for blowing up rafts and hooked it draw from a hookah.
It pushes 6 psi and I had no looks so I would say now I can be certain mine is not vacuum related.
It pushes 6 psi and I had no looks so I would say now I can be certain mine is not vacuum related.
TECH Resident
Joined: Apr 2007
Posts: 867
Likes: 218
From: Montgomery (Lake Conroe,) TX north of Houston
Unfortunately, it didn't fix the problem. The idle speed is still high so something is still wrong
.I would like to inspect the rest of that PVC hose but it goes along the passenger side of the intake manifold back towards the rear and the the cowl of the car gets in the way. I can't even see where it goes or where it connects to the engine. If someone could tell me where it goes and/or how to remove it, I would so that I could determine whether or not there is a leak in the hose or where it plugs into the engine.
TECH Resident
Joined: Apr 2007
Posts: 867
Likes: 218
From: Montgomery (Lake Conroe,) TX north of Houston
My car's idle problem has "morphed" in the last year or so.
About this time last year, I noticed that the high idle speeds were mostly gone when I wasn't using the ac. I did notice that I would almost always have high idle speeds with the ac on during warm Florida winter days but when the weather would cool down and I turned the ac off, my idle speeds were back to normal.
During the summer of 2015, I experienced the same thing with the ac on. Idle speeds were higher than they should be: 900-1000rpm with the ac on. If I turn the ac off, the idle will drop down to 700rpm. I've owned this car since I took delivery of it brand new on 13 Sept 2001 so I know it like the back of my hand. In it's younger days with the ac on, it did not idle at 900-1000rpm.
I know it's like comparing apples to oranges but my 5-sp, 1991 Mustang GT doesn't idle at 900-1000rpm with the ac on and neither does my automatic, 2001 F250SD diesel truck whether in gear or neutral.
At least the car doesn't frustrate me in the winter time. However, those summer high idle speeds really make me feel !
About this time last year, I noticed that the high idle speeds were mostly gone when I wasn't using the ac. I did notice that I would almost always have high idle speeds with the ac on during warm Florida winter days but when the weather would cool down and I turned the ac off, my idle speeds were back to normal.
During the summer of 2015, I experienced the same thing with the ac on. Idle speeds were higher than they should be: 900-1000rpm with the ac on. If I turn the ac off, the idle will drop down to 700rpm. I've owned this car since I took delivery of it brand new on 13 Sept 2001 so I know it like the back of my hand. In it's younger days with the ac on, it did not idle at 900-1000rpm.
I know it's like comparing apples to oranges but my 5-sp, 1991 Mustang GT doesn't idle at 900-1000rpm with the ac on and neither does my automatic, 2001 F250SD diesel truck whether in gear or neutral.
At least the car doesn't frustrate me in the winter time. However, those summer high idle speeds really make me feel
! 