TII runs better with a vacuum leak
08-01-06, 03:02 AM
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TII runs better with a vacuum leak
My 87 TII runs better when it has a vacuum leak?? What causes the idle to pulse between 1600-1900 rpm? TPS is adjusted, CAS is at "stock" setting, BAC has 11.9-12.1 ohm resistance. everything is plugged in and there is no vacuum leaks. give it one and the pulses go away and idles at 2000 rpm. But if you squeeze the hose between the intercooler and BAC, she dies. What's up with that?
08-01-06, 05:47 AM
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Throttle plate stuck? Throttle cable/cruise cable too tight? With the TB properly adjusted and the TPS set correctly, your car should idle at 750 rpms. Check to make sure the BAC is adjusted corrected also. U adjust it by grounding the 'adjustment plug' then adjusting the screw, but this has to be done after the TB is right. Is your fast idle wax sticking and keeping your car in fast idle? Best bet is to search the forums for tune up or dl the FSM.
08-01-06, 10:11 PM
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tried adjusting the BAC as the FSM stated. that only got the pulses to stop and a smooth idle at 1900 rpm. I pulled the UIM and going to replace the TB with my modded TB to see if that helps. also going the replace all the vacuum lines and gaskets again to see if that helps. it's almost like it's choking when it runs, the more vacuum leaks the better it runs.
08-01-06, 11:40 PM
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Hose between the intercooler and the BAC? That does not compute. I don't remember such a thing. Then again, I'm far from my car and FSM right now.
Hose b/t the BAC and the turbo outlet duct.....that computes.
Hose b/t the intercooler and the Air Bypass Solenoid...........that computes.
Nope, no hose b/t the intercooler and the BAC, says my memory.
Hose b/t the BAC and the turbo outlet duct.....that computes.
Hose b/t the intercooler and the Air Bypass Solenoid...........that computes.
Nope, no hose b/t the intercooler and the BAC, says my memory.
08-01-06, 11:44 PM
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Originally Posted by carzy driver
My 87 TII runs better when it has a vacuum leak?? What causes the idle to pulse between 1600-1900 rpm? TPS is adjusted, CAS is at "stock" setting, BAC has 11.9-12.1 ohm resistance. everything is plugged in and there is no vacuum leaks. give it one and the pulses go away and idles at 2000 rpm. But if you squeeze the hose between the intercooler and BAC, she dies. What's up with that?
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08-02-06, 01:43 AM
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Originally Posted by HAILERS
Hose between the intercooler and the BAC? That does not compute. I don't remember such a thing. Then again, I'm far from my car and FSM right now.
Hose b/t the BAC and the turbo outlet duct.....that computes.
Hose b/t the intercooler and the Air Bypass Solenoid...........that computes.
Nope, no hose b/t the intercooler and the BAC, says my memory.
Hose b/t the BAC and the turbo outlet duct.....that computes.
Hose b/t the intercooler and the Air Bypass Solenoid...........that computes.
Nope, no hose b/t the intercooler and the BAC, says my memory.
08-02-06, 01:48 AM
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Originally Posted by Apathy
Its idling fine at 2K because the ECU isnt trying to adjust the idle for some reason when it is that high. I know b/c my 7used to do the same thing. The idle would hunt between 1200-1700, but it was steady at 2000. I checked all the vaccuum lines and replaced all of them but still had the same issue. I replaced the BAC (because it was clogged) and the throttle body (b/c the wax was defective causing it to stick and I had another one so I just swapped it.)
08-02-06, 02:28 AM
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It runs better with the leak cause your idle is too rich.
With the leak, the AFM is closed more, which tricks the ECU into thinking there is less air going into the engine.
Also, the leak introduces more air into the engine.
All in all, if the idle is set rich, the leak will cause the engine to run "better".
Actually, I doubt you eliminated all the leaks.
How can you confirm that?
You can't do this visually.
Did you try the starting fluid / carb cleaner spray test?
The leak is triggering the pulsing.
Else, the TPS is adjusted bad or itself is bad.
-Ted
With the leak, the AFM is closed more, which tricks the ECU into thinking there is less air going into the engine.
Also, the leak introduces more air into the engine.
All in all, if the idle is set rich, the leak will cause the engine to run "better".
Actually, I doubt you eliminated all the leaks.
How can you confirm that?
You can't do this visually.
Did you try the starting fluid / carb cleaner spray test?
The leak is triggering the pulsing.
Else, the TPS is adjusted bad or itself is bad.
-Ted
08-02-06, 02:37 AM
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Originally Posted by RETed
It runs better with the leak cause your idle is too rich.
With the leak, the AFM is closed more, which tricks the ECU into thinking there is less air going into the engine.
Also, the leak introduces more air into the engine.
All in all, if the idle is set rich, the leak will cause the engine to run "better".
Actually, I doubt you eliminated all the leaks.
How can you confirm that?
You can't do this visually.
Did you try the starting fluid / carb cleaner spray test?
The leak is triggering the pulsing.
Else, the TPS is adjusted bad or itself is bad.
-Ted
With the leak, the AFM is closed more, which tricks the ECU into thinking there is less air going into the engine.
Also, the leak introduces more air into the engine.
All in all, if the idle is set rich, the leak will cause the engine to run "better".
Actually, I doubt you eliminated all the leaks.
How can you confirm that?
You can't do this visually.
Did you try the starting fluid / carb cleaner spray test?
The leak is triggering the pulsing.
Else, the TPS is adjusted bad or itself is bad.
-Ted
08-02-06, 02:46 AM
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But your idle is still high, right?
Check your dashpot (tII has them too right?) If you took things apart, maybe that is misadjusted.
Just something to try, it happened to me in a moment of stupidity. I could tell other stories, but I don't want to admit to them
Check your dashpot (tII has them too right?) If you took things apart, maybe that is misadjusted.
Just something to try, it happened to me in a moment of stupidity. I could tell other stories, but I don't want to admit to them
Last edited by KeeganP; 08-02-06 at 02:52 AM.
08-02-06, 02:52 AM
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yah, it still runs around 1600-1700 rpm.
When I had everything disassembled, I didn't touch anything on the TB. I just removed the TB elbow/TB/UIM and put them away while I was rebuilding the motor. The modded TB I'm replacing the dirty stock TB with has the thermowax removed, the forward most secondary butterflies removed and I plugged the holes with threaded plugs and JB weld.
When I had everything disassembled, I didn't touch anything on the TB. I just removed the TB elbow/TB/UIM and put them away while I was rebuilding the motor. The modded TB I'm replacing the dirty stock TB with has the thermowax removed, the forward most secondary butterflies removed and I plugged the holes with threaded plugs and JB weld.
Last edited by carzy driver; 08-02-06 at 03:00 AM.
08-02-06, 02:58 AM
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^^^ That's a very good place to start. That's what I thought too, but it was my dashpot holding the throttle open to far. I don't know too much about tII so I'm just throwing out an idea. Hope you figure it out.
08-02-06, 03:06 AM
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I replaced all hoses and lines when I reassembled the longblock. As for a dashpot hanging up and causing the throttle to stick open, I doubt that. I tried forcing the TB closed, even backed off the adjusting screw/bolt that has the jam nut and that still didn't do anything for the idle. checked for leaks using a can of starting fluid, only to find a split vacuum cap. replaced it and still having problems.
08-02-06, 03:13 AM
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Well.... I don't know. Wish I could help more. 
The only things I could think of I said. I can't stress enough though, intake/turbo leaks, and throttle bindage, and TPS (didn't mention that before) problems. Other than that, I'm out of ideas, but I'm an NA guy.
The only things I could think of I said. I can't stress enough though, intake/turbo leaks, and throttle bindage, and TPS (didn't mention that before) problems. Other than that, I'm out of ideas, but I'm an NA guy.
08-02-06, 07:40 AM
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Waitaminute...
Are you complaining about a high idle or a pulsing idle?
Did you hook up the stock cruise control back?
Did you check if the cruise control cable isn't too tight?
Did you shoot starting fluid on top of the engine?
The fuel injector lower grommets are notorious for leaking...
-Ted
Are you complaining about a high idle or a pulsing idle?
Did you hook up the stock cruise control back?
Did you check if the cruise control cable isn't too tight?
Did you shoot starting fluid on top of the engine?
The fuel injector lower grommets are notorious for leaking...
-Ted
08-02-06, 01:23 PM
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Originally Posted by Karack
i believe i found what his problem was, the bypass air valve on top of the UIM was taken off and a straight piece of vacuum line put in place causing a large internal vacuum leak past the throttle body, hopefully this cures it.
08-02-06, 01:27 PM
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Originally Posted by Karack
well to me it sounds like multiple problems but gotta start somewhere.
the choking issue sounds like a rich condition but for what reason? did you install larger injectors without compensating for them? bigger fuel pump?
the choking issue sounds like a rich condition but for what reason? did you install larger injectors without compensating for them? bigger fuel pump?