**B-R-A-A-A-A-A-A** <-- WTF is causing this?!?
08-21-03, 07:37 PM
#1
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**B-R-A-A-A-A-A-A** <-- WTF is causing this?!?
This problem has been plaguing me all summer and I'm starting to daydream about shoving some dynamite up the tailpipe when I drive my 7.
I posted about this sometime last month. Then the problem went away, and I assumed it was because of two damaged vac lines that I had replaced. Now it's back and I don't know WTF is causing it. While some of the symptoms scream vac leak, I'm wondering if it's maybe a component failure, like a valve in the vac sys or a sensor somewhere. I'm planning on swapping out the ECU and AFM tomorrow evening to see if things change.
And now the problem...
My goddamn car PURRS.
Sometimes it rarely happens, sometimes I can't escape it. And when I mean sometimes we're talking minute to minute, stoplight to stoplight. Here's how some of it goes.
----
We're sitting at a stoplight. In neutral, clutch out, brake in. Idle is normal at 750. The light changes. We pull away normally and all is good.
Now we're coming up to the next light. We downshift through the gears until we reach 2nd, then we put the clutch in and pop the shifter out into neutral and release the clutch and use the brake to stop. The tach falls from wherever it was, but instead of dropping down to 750 it gets hung up at 1500, or maybe sometimes 1000. And instead of simply humming at those revs, the motor goes B-R-A-A-A-A-A-A like a long, fast, never-ending stacatto burp.
Sometimes I can kill this by shifting into a gear (never letting the clutch out.) The revs will struggle for a moment and then drop down to idle. I can then shift back into neutral and let the clutch out and all is normal. Other times, it will only drop 200-300 revs and the B-R-A-A-A-A-A will get louder and deeper until I shift back into neutral, where it returns to its regular B-R-A-A-A-A-A.
Please note. The clutch itself has no effect - the tranny must be put in gear, and it doesn't seem to matter which gear is chosen.
Now the other circumstances when it happens, and in this instance it ALWAYS happens.
We're cruising down a street. We're rolling at the speed we want to be at, so we're holding the gas pedal at that sweet spot where we're just holding our current speed.
And there's the noise again. B-R-A-A-A-A-A. It's fainter now, maybe because of wind and road noise and all that, but it's definitely there.
The symptom that screams vac leak is that once in a long, long while the idle, while doing this purr, will bounce across a few hundred rpms.
I have:
- replaced all of the vac lines with new silicone, and have re-replaced several of those since.
- installed new injector grommets and o-rings all around.
- Permatex'ed the gasket between the intake manifold and the dynamic chamber.
- checked and re-checked for vac leaks, including a half hour under the hood this afternoon with a garden hose. I've had my manifolds off at least a dozen times this year and I *know* where everything is and where to point the hose.
- removed the OMP and properly blocked off the relevent openings.
- not done the TB mod.
- installed an S-AFC long before this started, but the S-AFC has yet to be tuned.
The only other things I can think of are the cam and the fast idle cam, which I was messing with early this summer when I had an idle problem (since resolved.)
The only guy I trust to take a look at this with me is in Italy until next month.
Suggestions?
I posted about this sometime last month. Then the problem went away, and I assumed it was because of two damaged vac lines that I had replaced. Now it's back and I don't know WTF is causing it. While some of the symptoms scream vac leak, I'm wondering if it's maybe a component failure, like a valve in the vac sys or a sensor somewhere. I'm planning on swapping out the ECU and AFM tomorrow evening to see if things change.
And now the problem...
My goddamn car PURRS.
Sometimes it rarely happens, sometimes I can't escape it. And when I mean sometimes we're talking minute to minute, stoplight to stoplight. Here's how some of it goes.
----
We're sitting at a stoplight. In neutral, clutch out, brake in. Idle is normal at 750. The light changes. We pull away normally and all is good.
Now we're coming up to the next light. We downshift through the gears until we reach 2nd, then we put the clutch in and pop the shifter out into neutral and release the clutch and use the brake to stop. The tach falls from wherever it was, but instead of dropping down to 750 it gets hung up at 1500, or maybe sometimes 1000. And instead of simply humming at those revs, the motor goes B-R-A-A-A-A-A-A like a long, fast, never-ending stacatto burp.
Sometimes I can kill this by shifting into a gear (never letting the clutch out.) The revs will struggle for a moment and then drop down to idle. I can then shift back into neutral and let the clutch out and all is normal. Other times, it will only drop 200-300 revs and the B-R-A-A-A-A-A will get louder and deeper until I shift back into neutral, where it returns to its regular B-R-A-A-A-A-A.
Please note. The clutch itself has no effect - the tranny must be put in gear, and it doesn't seem to matter which gear is chosen.
Now the other circumstances when it happens, and in this instance it ALWAYS happens.
We're cruising down a street. We're rolling at the speed we want to be at, so we're holding the gas pedal at that sweet spot where we're just holding our current speed.
And there's the noise again. B-R-A-A-A-A-A. It's fainter now, maybe because of wind and road noise and all that, but it's definitely there.
The symptom that screams vac leak is that once in a long, long while the idle, while doing this purr, will bounce across a few hundred rpms.
I have:
- replaced all of the vac lines with new silicone, and have re-replaced several of those since.
- installed new injector grommets and o-rings all around.
- Permatex'ed the gasket between the intake manifold and the dynamic chamber.
- checked and re-checked for vac leaks, including a half hour under the hood this afternoon with a garden hose. I've had my manifolds off at least a dozen times this year and I *know* where everything is and where to point the hose.
- removed the OMP and properly blocked off the relevent openings.
- not done the TB mod.
- installed an S-AFC long before this started, but the S-AFC has yet to be tuned.
The only other things I can think of are the cam and the fast idle cam, which I was messing with early this summer when I had an idle problem (since resolved.)
The only guy I trust to take a look at this with me is in Italy until next month.
Suggestions?
Last edited by Amur_; 08-21-03 at 07:41 PM.
08-21-03, 07:51 PM
#3
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It's disconnected in mine, too. But it's ALWAYS been disconnected... I have trouble believing that it would take 3 years for a prob to develop from it's being unplugged...
edit: Waitaminute. Let's make sure we're talking about the same thing. The clutch switch (item no. 7, page 6-5, s4 FSM) is unplugged on my 7. 5th gear switch? Still connected AFAIK.
another edit: s4 FSM, page 7A-4, item no. 9. Reverse/5th gear connector. This component is 100% AFAIK.
edit: Waitaminute. Let's make sure we're talking about the same thing. The clutch switch (item no. 7, page 6-5, s4 FSM) is unplugged on my 7. 5th gear switch? Still connected AFAIK.
another edit: s4 FSM, page 7A-4, item no. 9. Reverse/5th gear connector. This component is 100% AFAIK.
Last edited by Amur_; 08-21-03 at 07:59 PM.
08-21-03, 10:41 PM
#4
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Holy ****, i used to have the same damn problem, I SWEAR!, one day it just kinda went away, and nver came back, i dunno what caused it, or what got rid of it but i know what you mean. I would be very interested in finding out what the hell causes this situation.
-Chris
-Chris
08-22-03, 08:07 AM
#5
I had a *similar* problem, but I'm not sure that it was the same thing. It turned out that I had two problems.
When I was driving at a constant speed, and that BRAAAAAAAAAAAAA noise started - if I let off or gave it more throttle the noise went away. The problem was my TPS. I'd adjust it - and everything would be alright. A week later, I'd check the ohms, and they would be off again, so I'd have to re adjust it. I replaced the TPS, and the problem hasn't appeared since.
That solved one aspect of the noise, but it still happened when I was stationary. I opened the hood, unplugged the BAC valve, and the noise hasn't appeared since.
Good Luck!
When I was driving at a constant speed, and that BRAAAAAAAAAAAAA noise started - if I let off or gave it more throttle the noise went away. The problem was my TPS. I'd adjust it - and everything would be alright. A week later, I'd check the ohms, and they would be off again, so I'd have to re adjust it. I replaced the TPS, and the problem hasn't appeared since.
That solved one aspect of the noise, but it still happened when I was stationary. I opened the hood, unplugged the BAC valve, and the noise hasn't appeared since.
Good Luck!
08-22-03, 06:17 PM
#6
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It still happens with the BAC unplugged - checked that yesterday. TPS has been checked several times throughout this. It's been fine.
Here's something I forgot to include yesterday, but I've been thinking about it a lot since.
Up until this started it was easy as hell to get afterburn in my 7. Jogging the throttle around redline would produce endless bangs. The engine had always been like this.
Now, at about the same time this problem started, my afterburn disappeared completely. Jogging the throttle at redline produces NOTHING.
As you'll see below, I tested the AAV and it totally failed. If the device meant to compensate for afterburn is dead, then why isn't she producing afterburn anymore? I have a strong feeling that this is a relevent clue, but I don't know what it means.
I haven't put my spare AFM or ECU in yet.
Switching Solenoid Valve (s4 FSM, 4-28)
- failed the 'suck' test (first step in diagnostic.)
- passed 'blow' test (blow into hose A and air flows from hose B.)
- not sure about 'blow and zap' test (apply power and blow through hose A and air flows from vent.) The manifolds were hot when I did this and I was just lucky to blow into the hose. Also, this was after a full day of work so my fingertip (the one on the vent) wasn't exactly at its most sensitive.
Anti-Afterburn Valve (s4 FSM, 4-36)
- totally failed.
Air Control Valve
- wanted to check it but ran out of time...
Thoughts?
Here's something I forgot to include yesterday, but I've been thinking about it a lot since.
Up until this started it was easy as hell to get afterburn in my 7. Jogging the throttle around redline would produce endless bangs. The engine had always been like this.
Now, at about the same time this problem started, my afterburn disappeared completely. Jogging the throttle at redline produces NOTHING.
As you'll see below, I tested the AAV and it totally failed. If the device meant to compensate for afterburn is dead, then why isn't she producing afterburn anymore? I have a strong feeling that this is a relevent clue, but I don't know what it means.
I haven't put my spare AFM or ECU in yet.
Switching Solenoid Valve (s4 FSM, 4-28)
- failed the 'suck' test (first step in diagnostic.)
- passed 'blow' test (blow into hose A and air flows from hose B.)
- not sure about 'blow and zap' test (apply power and blow through hose A and air flows from vent.) The manifolds were hot when I did this and I was just lucky to blow into the hose. Also, this was after a full day of work so my fingertip (the one on the vent) wasn't exactly at its most sensitive.
Anti-Afterburn Valve (s4 FSM, 4-36)
- totally failed.
Air Control Valve
- wanted to check it but ran out of time...
Thoughts?
Last edited by Amur_; 08-22-03 at 06:22 PM.
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08-22-03, 08:24 PM
#9
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Originally posted by Black13B
Anti-Afterburn valve working erratically?
How/When does it work/activate?
Anti-Afterburn valve working erratically?
How/When does it work/activate?
Read the post again.
08-22-03, 08:35 PM
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I had this problem in my Z/06.
I was driving at moderate speed... then I hear this BRAAAAAAAA sound, and it kept getting louder. I step on the throttle, and it got more quiet. I let up on the gas, and brraaaaaAAAAAAA - it got louder again.
Finally, at a red light, I discovered the source.
It was a honda civic...
I was driving at moderate speed... then I hear this BRAAAAAAAA sound, and it kept getting louder. I step on the throttle, and it got more quiet. I let up on the gas, and brraaaaaAAAAAAA - it got louder again.
Finally, at a red light, I discovered the source.
It was a honda civic...
08-22-03, 08:39 PM
#11
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Originally posted by 1BADRIDE
I had this problem in my Z/06.
I was driving at moderate speed... then I hear this BRAAAAAAAA sound, and it kept getting louder. I step on the throttle, and it got more quiet. I let up on the gas, and brraaaaaAAAAAAA - it got louder again.
Finally, at a red light, I discovered the source.
It was a honda civic...
I had this problem in my Z/06.
I was driving at moderate speed... then I hear this BRAAAAAAAA sound, and it kept getting louder. I step on the throttle, and it got more quiet. I let up on the gas, and brraaaaaAAAAAAA - it got louder again.
Finally, at a red light, I discovered the source.
It was a honda civic...
Get the **** out of my thread!
08-24-03, 01:20 AM
#13
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Originally posted by silverrotor
So, how do you suspect your TPS needs to be swapped?
So, how do you suspect your TPS needs to be swapped?
PMs with hypntyz7. I may have local leads on a replacement. I didn't get to the test today (Saturday.) Will try tomorrow (Sunday.)
You still have your 'spare' one?
08-24-03, 02:07 AM
#14
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Geez. A post by Amur that doesn't make me laugh. And I don't know what to say except I hope you figure the problem out...and I hope it never happens to me.
Please post a picture if you decide to go the tailpipe dynomite route.
Good luck
Nat
Please post a picture if you decide to go the tailpipe dynomite route.
Good luck
Nat
08-28-03, 05:21 PM
#15
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Originally posted by fcfdfan
Geez. A post by Amur that doesn't make me laugh. And I don't know what to say except I hope you figure the problem out...and I hope it never happens to me.
Geez. A post by Amur that doesn't make me laugh. And I don't know what to say except I hope you figure the problem out...and I hope it never happens to me.
With hypntyz7's help and insight, I've determined that it is the TPS. I've been driving my 7 for the last 3 days with the TPS unplugged and the problem vanished. The poor girl suffered hesitation problems whenever I got too heavy on the gas, but otherwise she ran ok.
Here is hypntyz7's PM, posted with permission.
Some later comments from him follow the main body...
Originally written by hypntyz7
I'm not sure I remember, and you didnt say, but I think this is an s4 t2? [she's an s4 NA]
Your description of "brraaaa" is unusual, to say the least. Your description of purring, and some imagination, lead me to believe you're talking about a common condition on s4 t2's.
You ever been around a 7 running on one rotor? blown apex's, you know? IF you have, you'll know the distinct sound they have, a really weak, pitiful purring sound. Often s4 t2's do this upon decel, or at the *very* fine line between light throttle and light decel, such as 1 or 2 gear in a neighborhood late at night. When the thing crosses the line into decel, it sounds like it drops a rotor, has a very light vibrating sensation, and loses some power. Applying ever so slightly more throttle brings the other rotor back on (or sensation of such) with an abrupt jarring grab. The sensation is sort of like an on/off switch, and you can't be gentle enough to avoid it.
I have found this to be an issue with the TPS. Yes, I know you said you tested it, but the fact of the matter is that you can test one all day long and if you car doesnt like it, it is no longer going to operate properly with it on there. I had an s4 t2 that I ran for a long time with NO tps and it ELIMINATED this sensation altogether...you had a very gradual progression from light throttle to decel and back with no jarring, vibration, or "dropping the rotor".
IF a TPS gets out of whack enough, they can cause idle problems, even a bouncing idle that revs freely up and puuuurrs back down on one rotor, then revs back up freely, repeat. A local guy's car does this badly when cold, and somewhat when warm.
My suggestion is to get in there and play with the TPS. Unplug it, readjust your idle, and go for a drive. You'll be SURPRISED at the smoothness you regain. Note that, however, some cars I have tried this on refused to run well without a TPS, but most happily accept it after idle is readjusted.
OF course, my guess at the sound you are actually describing could be way off, so tell me if Im right or not.
--
You can test a TPS all day long with voltmeters and the like, but bottom line you cant tell if it is 100% or 80% or 40%. A TPS that may work on my car might not work well on yours. A TPS that works well on your car might work well on mine, but not well on another friend of ours, while it "tests" good all the time. See what Im saying? Everybody's car is a bit different for no real explainable reason.
--
yeah, that's the key. the whole "remove your tps" thing isnt thrown out there as a permanent solution for most, but another troubleshooting method. IF a TPS is bad enough, the car will run much better without it, though.
--
just relaying experience, much of it unorthodox by others' standards in the community. For instance, some guy would be talking about having injectors cleaned or some such BS when he probably has no clue what you're even talking about as a problem, he is just re-relaying the information commonly thrown around. I, on the other hand, relay firsthand experience, no matter how much (or little) sense it may make to the masses.
I'm not sure I remember, and you didnt say, but I think this is an s4 t2? [she's an s4 NA]
Your description of "brraaaa" is unusual, to say the least. Your description of purring, and some imagination, lead me to believe you're talking about a common condition on s4 t2's.
You ever been around a 7 running on one rotor? blown apex's, you know? IF you have, you'll know the distinct sound they have, a really weak, pitiful purring sound. Often s4 t2's do this upon decel, or at the *very* fine line between light throttle and light decel, such as 1 or 2 gear in a neighborhood late at night. When the thing crosses the line into decel, it sounds like it drops a rotor, has a very light vibrating sensation, and loses some power. Applying ever so slightly more throttle brings the other rotor back on (or sensation of such) with an abrupt jarring grab. The sensation is sort of like an on/off switch, and you can't be gentle enough to avoid it.
I have found this to be an issue with the TPS. Yes, I know you said you tested it, but the fact of the matter is that you can test one all day long and if you car doesnt like it, it is no longer going to operate properly with it on there. I had an s4 t2 that I ran for a long time with NO tps and it ELIMINATED this sensation altogether...you had a very gradual progression from light throttle to decel and back with no jarring, vibration, or "dropping the rotor".
IF a TPS gets out of whack enough, they can cause idle problems, even a bouncing idle that revs freely up and puuuurrs back down on one rotor, then revs back up freely, repeat. A local guy's car does this badly when cold, and somewhat when warm.
My suggestion is to get in there and play with the TPS. Unplug it, readjust your idle, and go for a drive. You'll be SURPRISED at the smoothness you regain. Note that, however, some cars I have tried this on refused to run well without a TPS, but most happily accept it after idle is readjusted.
OF course, my guess at the sound you are actually describing could be way off, so tell me if Im right or not.
--
You can test a TPS all day long with voltmeters and the like, but bottom line you cant tell if it is 100% or 80% or 40%. A TPS that may work on my car might not work well on yours. A TPS that works well on your car might work well on mine, but not well on another friend of ours, while it "tests" good all the time. See what Im saying? Everybody's car is a bit different for no real explainable reason.
--
yeah, that's the key. the whole "remove your tps" thing isnt thrown out there as a permanent solution for most, but another troubleshooting method. IF a TPS is bad enough, the car will run much better without it, though.
--
just relaying experience, much of it unorthodox by others' standards in the community. For instance, some guy would be talking about having injectors cleaned or some such BS when he probably has no clue what you're even talking about as a problem, he is just re-relaying the information commonly thrown around. I, on the other hand, relay firsthand experience, no matter how much (or little) sense it may make to the masses.
08-28-03, 07:11 PM
#17
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So go unplug your TPS, set your idle and see what you get...
New TPS has been ordered from dealership. Getting it for 20% off thanks to connections.
New TPS has been ordered from dealership. Getting it for 20% off thanks to connections.
08-28-03, 07:48 PM
#18
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Originally posted by Amur_
So go unplug your TPS, set your idle and see what you get...
New TPS has been ordered from dealership. Getting it for 20% off thanks to connections.
So go unplug your TPS, set your idle and see what you get...
New TPS has been ordered from dealership. Getting it for 20% off thanks to connections.
The TPS I had for you was just sold today. I hadn't heard from you, and someone else was in dire need, so I let it go.
08-29-03, 03:03 PM
#22
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Before you write off the TPS - try shooting some spray contact cleaner in between the plunger & the sleeve.
Work it in, blow it out, repeat.
I found CRC QD contact cleaner in the electric Dept at Home Depot.
It's also good for other contacts like the logicon sliders, the door lock sensors.
Mine came back to life - it was just dirty inside.
Work it in, blow it out, repeat.
I found CRC QD contact cleaner in the electric Dept at Home Depot.
It's also good for other contacts like the logicon sliders, the door lock sensors.
Mine came back to life - it was just dirty inside.
08-29-03, 03:38 PM
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Amur:
If your AAV does not hold a vacuum, the diaphragm is toast and you have a vacuum leak.
The switching solenoid valve just switching the air pump flow to either port air or split air, so it's strictly for emissions. Won't create a vac leak.
You should check the relief valve diaphragm and the solenoid that goes with it to make sure the air pump is not dumping overboard all the time, that will complete the ACV check.
Nice post BTW and thanks Kevin for the info
Hugues -
If your AAV does not hold a vacuum, the diaphragm is toast and you have a vacuum leak.
The switching solenoid valve just switching the air pump flow to either port air or split air, so it's strictly for emissions. Won't create a vac leak.
You should check the relief valve diaphragm and the solenoid that goes with it to make sure the air pump is not dumping overboard all the time, that will complete the ACV check.
Nice post BTW and thanks Kevin for the info
Hugues -
08-29-03, 05:21 PM
#24
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Originally posted by hugues
Amur:
If your AAV does not hold a vacuum, the diaphragm is toast and you have a vacuum leak.
The switching solenoid valve just switching the air pump flow to either port air or split air, so it's strictly for emissions. Won't create a vac leak.
You should check the relief valve diaphragm and the solenoid that goes with it to make sure the air pump is not dumping overboard all the time, that will complete the ACV check.
Nice post BTW and thanks Kevin for the info
Hugues -
Amur:
If your AAV does not hold a vacuum, the diaphragm is toast and you have a vacuum leak.
The switching solenoid valve just switching the air pump flow to either port air or split air, so it's strictly for emissions. Won't create a vac leak.
You should check the relief valve diaphragm and the solenoid that goes with it to make sure the air pump is not dumping overboard all the time, that will complete the ACV check.
Nice post BTW and thanks Kevin for the info
Hugues -
I'll check those this weekend.
Kevin is a Forum oracle. 
And I'll try the contact cleaner, too.