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Discussion Starter · #1 ·
i have a 2000 Mustang GT i just recently installed a 75mm throttle body and upper intake plenum (both Power Products) the only reason i picked these 2 is because they were on craigs list cheap, so i couldn't pass them up, but anyways...i have been having problems with bad idling (700 rpms down to 500rpms and then back up to around 1000) and then it would stall..i would come to a stop and my car would just die...i put a new idle control valve on and that still hasn't fixed the problem...my next step was to go ahead and replace the throttle control sensor to see if that would do anything...any other suggestion please let me know before i take these two off and sell them and just put the stock back on..another question is what are the barbed fittings that come with the upper intake plenum for?.. should i try using the bigger sized one?
 

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Two things I can think of:

(1) The throttle plate set screw has been adjusted from the factory setting.
(2) There is a vacuum/air leak somewhere or a vacuum line not connected.

If you disconnected the battery during the install, it will take a few drives for the computer to relearn its parameters. If this is the case, start the car and let it try to idle without touching the gas pedal. If it stalls, restart it and let it try until it relearns what it needs to idle smoothly.

The different sized barbs are to allow the intake to be used in a 96-04 Mustang 4.6L engine which had 2 or 3 different vacuum line/manifold connection hose sizes over the years. Use the one that fits your application.
 

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I would try the throttle plate screw first unless it's an obvious vacuum leak or diconnected hose. I believe the procedure to set the screw properly was to back the srcrew .010 off the plate using a feeler gauge. Let the car war up to normal op. temp. then turn the screw back towards the plate a one full rotation. This is the screw on the TB. You will probably need an allen wrench to do this.
 

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1.) Have you diconnected the batt for 30 min and let the ecu reset?? If not, do it.

2.) the only other problem could be a leak.
 

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1.) Have you diconnected the batt for 30 min and let the ecu reset?? If not, do it.

2.) the only other problem could be a leak.
My advice, dont go playing with screws and what not. Try these steps first. If you adjust it you wlll NEVER get it right.
 

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the car was running right before the upper intake swap? if thats the case, just use all of your stock parts except the actual PLENUM and the actual TB. use all original hardware. if it doesnt work then you know why it was so cheap.

edit: oh yeah make sure you tighten everything down in about 1/2-1 turn incriments. like the plenum its very important. + use the gaskets. You only need 3 things to get the car running. spark/gas/vaccum. plenum is all vaccum.. make sure its sealed! maybe use a black sealer around the bases after the gasket sealer and bolts are tightened.

edit again: use the fitting that you can slide your hose over not that easy. like where you have to push and you cant pull it off without a bit of force :nogrinner
 

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oh yeah for future facts. you cant set idle with the TB anymore. not on these cars. even with pedal fully depressed and tb blade fully closed. your always going to get the idle your computer tells it to give it. So i wouldnt suggest disconnected battery AT ALL. this will only throw off your i/m monitors making it a pain in the ass to reset. should be a SIMPLE swap. 100% sounds like a vaccum leak though :bigthumbsup
 

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The instructions that came with my BBK plenum say to disconnect the battery to let the computer reset after install. I did not do this and my car ran like you described until I read the instructions (who does that first anyway) and disconnected the battery problem solved. And also in the instructions and in the manual it tells how to set the base idle with the idle set screw, you have to do this first before the computer can use the IAC valve to control the idle.
 

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You shouldnt have to set the frigan idle screw. i like BBK plenums/TB combos but that is just bullshlachen..
 

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Discussion Starter · #10 ·
thanks alot for all the input i will try to do some of the things listed above when i get a chance, and i will post an update with the results...i have had the battery off for a full day to let it reset, i put it back on and let it idle to the normal temp, idled great...i took it for a drive and played around alittle in it and then came to a stop and it would idle really low (500 rpm) or just stall...should i try and switch the gaskets out with new ones?
 

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you need to check the volts to your tps sensor thats more then likely your problem.that needs adusting alot of times when changing to a new TB. It will cause an eratic idle if not right.
 

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You shouldnt have to set the frigan idle screw.
Sometimes yes and sometimes no when you change the TB and/or the plenum. You have to set the base idle and then the IAC takes over from there (if the base idle is not correct). The tolerance on the screw from the factory (and the aftermarket) is not near tight enough to make everyone’s car idle the same, which is why it is there. That is why when you set it to the base idle (which is 500PRM I think) you have to disconnect the IAC so the computer does not try to adjust the idle while you are tinkering with the set screw.

This might be or might not be the prolbem but is one variable that can easily be checked and eliminated:bigthumbsup
 

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Discussion Starter · #13 ·
how do i go about checking that?..would it help to try and replace the TPS?..also i talked to a place around where i live that work on mustangs, and he seems to think i need to have my car tuned, could this also be a problem or is he trying to get my money?...
 

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Discussion Starter · #14 ·
well i still am having problems with the car!!.. i installed new gaskets, new TPS and idle control valve...had the battery off and everything...started it up, idled great, no hesitation or anything...took it out for a drive and it was doing good...took it on the highway and hit about 110 to open it up, came to a red light and what do you know it died!!!im wondering if i should just take everything off and put the old stuff back on. let me know if you think of something else to try...should i try and put hose clamps on all the hose's to make sure everything is tight?...its really getting aggravting...
 

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still need to let the computer adapt.the mix is controlled in cells.which is better understood as events,stopping from high speed is not the same event of stopping from normal speed.takes a few different trips,driven slow,normal,fast,to let the computer adapt,so if is driving ok at regular speeds and then,all the sudden,it's stall while stopping from high speed at the first drives,it is not a biggie.start it up again and let it eat.this is all making sure there is no vacuum leaks,(hoses disconnected,bolts torqued uneven,teared or broken gaskets),electrical connectors disconnected or incorrect idle screw adjustment.differs with the engine,there is no written specs.with the iac disconnected try to reach minimun engine speed without surging or stalling,move the screw slowly.the last is to adjust the idle screw.rev the engine in betwen adjustments.then when you get it right, find the next chevy and beat him up.:bigthumbsup
 

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Discussion Starter · #16 ·
still need to let the computer adapt.the mix is controlled in cells.which is better understood as events,stopping from high speed is not the same event of stopping from normal speed.takes a few different trips,driven slow,normal,fast,to let the computer adapt,so if is driving ok at regular speeds and then,all the sudden,it's stall while stopping from high speed at the first drives,it is not a biggie.start it up again and let it eat.this is all making sure there is no vacuum leaks,(hoses disconnected,bolts torqued uneven,teared or broken gaskets),electrical connectors disconnected or incorrect idle screw adjustment.differs with the engine,there is no written specs.with the iac disconnected try to reach minimun engine speed without surging or stalling,move the screw slowly.the last is to adjust the idle screw.rev the engine in betwen adjustments.then when you get it right, find the next chevy and beat him up.:bigthumbsup
i'm thinking the idle set screw is messed up, i tried to mess with it and i couldnt get it to idle good at all, it was either way too high or way to low...so all in all i just took the throttle body and plenum off and they are both going on craigslist...i put the factory parts back on and the car is running great...by the time that would have set itself to the settings it needed my starter was gonna go out, it got to the point where it was having trouble starting, so i took the easy way out..thanks for all the help, but i guess im no mechanic when it comes to this kind of stuff
 
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