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JimG

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My 87 GN has started making an abnormal whistling sound when slightly opening the throttle.
It seems to have affected drivability somewhat with a little hesitation off idle.
Intake leak? vacuum leak?
Any thoughts?
thanks
Jim
 
Sometimes I can get my car to do that, its a tiny little spot on the throttle that will. But never affected anything. Check ALL the vacuum lines, also post your idle BLM if you have a scan tool. That will help to determine if it is indeed a vacuum leak and not just a cool sound... :) If the vacuum lines are old and turn your hands black just from touching them in the slightest, I would start there and replace as many as possible... Mine were horrible, barely even rubber anymore.
 
If it's effecting drivability and the blms are off I would suspect a vacuum leak. If it's just a light throttle whistle with no apparent origin and no associated issues then I would suspect the little seals where the shaft for the throttle blade goes through the housing.
 
thanks for the tips

you guys.
Yes, the vacuum lines are old and dirty. What is recommended for using as replacements.
Had the DS going at the time,but will take note of the idle BLM's tonight. What #'s should I be wanting to see?
thanks again
Jim
 
update

Well, checked out the vacuum lines and nothing seemed out of the ordinary, although they will all be changed at some point in the future.
Please review the following DS readings taken at warmed up idle.

RPM 775
temp 165 degrees F
TPS .48
LV8 30
MAF 4 g/s
02v 675-682
Int 128
BLM 142

I may have ommited some other readings at the time. Of curiousity, while idling I removed the vacuum line off of the canister line before the check valve, and with it uncovered the idle increased slightly, but i registered no changes to the above readings.
I also removed the vacuum line to the FPR independantly, and got the same results.
I dont think i have any issues with DS as it tracks the cells etc when driving or applying throttle.
I am still way low on the learning curve guys. Is this info of any value. Does it lead to anything other than Jim needs to spend more time leaing about his car??
I appreciate all advise and criticism!
thanks
Jim
 
Look at the ds and see where all of the blm cells are at. If you're pretty universally high in all cells then you should turn up the fuel pressure. If your idle cell is the only on that's high then I would still suspect some sort of vacuum/exhaust leak. I like to see around .44 on the tps at idle and also, what are your IAC counts?

EDIT
I may have ommited some other readings at the time. Of curiousity, while idling I removed the vacuum line off of the canister line before the check valve, and with it uncovered the idle increased slightly, but i registered no changes to the above readings.

Make sure you're in closed loop because even if the idle changes if you're open loop the ecm isn't going to make any adjustments.
 
If you are running a TT chip I would suggest resetting the ECM (orange wire by the battery with the black plug) and then starting the car on first key-on then letting it warm up to operating temp. Then shutdown the the car, start it back up again and check the numbers once more. Maybe your car has learned that idle BLM from a previous issue and now it just needs to correct itself. Thing about TT chips is they only run a closed loop idle the first time you turn the key-on/start it. After that they run open loop idle for smoothness based on what it learned the first time you started it.

HTH
 
Look at the ds and see where all of the blm cells are at. If you're pretty universally high in all cells then you should turn up the fuel pressure. If your idle cell is the only on that's high then I would still suspect some sort of vacuum/exhaust leak. I like to see around .44 on the tps at idle and also, what are your IAC counts?

EDIT


Make sure you're in closed loop because even if the idle changes if you're open loop the ecm isn't going to make any adjustments.


BlackBandit,
thanks. other cells are high but not at 142. I am running a TT chip, to which i have adjusted the 1st gear timing back to 16 degrees due to low gear knock. I will continue to work on tps settings. I think I didnt note the IAC as they were between the recommended 10-30.
Jim
 
If you are running a TT chip I would suggest resetting the ECM (orange wire by the battery with the black plug) and then starting the car on first key-on then letting it warm up to operating temp. Then shutdown the the car, start it back up again and check the numbers once more. Maybe your car has learned that idle BLM from a previous issue and now it just needs to correct itself. Thing about TT chips is they only run a closed loop idle the first time you turn the key-on/start it. After that they run open loop idle for smoothness based on what it learned the first time you started it.

HTH
thanks for that helpful info. I will reset the ECM as you have advised and report back.
You guys are great.
Jim
 
Maybe you'll get lucky... :)

The TPS is kind of a preference thing except for the fact that it must stay below .50 volts for the chip to recognize idle. As long as it doesn't jump up to .50 at all then I would say don't bother. Some people like that extra cushion, mine is at .48 right now and I don't have issues. If you do adjust it, make sure that WOT reads 4.5v or above or the chip may not see WOT. The TT chip might be less than 4.5v for WOT, but over 4.5v won't hurt. Eric may have to confirm the exact voltage needed for WOT. I get 4.6-4.7v depending on how hard I stomp on it. :)
 
update

Well, reset the ECM last night and saw no significant difference in the BLM readings. It did drop to 141 for a moment or two though.
I watched my TPS closely and it does occasionaly jump up to the dreaded .50, so I guess i should try to lower that some more.
Off to the hardware store tonight for a propane bottle and continue on the hunt for vacuum leaks.
Are there other ways to hunt for exhaust leaks other than pouring seafoam or the like into the engine. Would spraying some substance at the suspect locations possibly help?
As usual, all of your wisdom and experienced advise is appreciated.
thanks
Jim
 
In my experience the best way to check for exhaust leaks is to listen with a length of hose and look for carbon tracks. The most common place to look is on the ds header. There may be a crack between #3 and #5. Also, if you have gaskets check them carefully for blowouts.
 
My 87 GN has started making an abnormal whistling sound when slightly opening the throttle.
It seems to have affected drivability somewhat with a little hesitation off idle.
Intake leak? vacuum leak?
Any thoughts?
thanks
Jim

If everything else checks out, double check all the IC hoses and clamps. Sometimes if the clamps are loose or if there is a crack in the IC hose, it will make a whistling sound as you give gas.


HTH

Prasad
 
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