can someone help me with a vacuum leak?

[fawcett]

seems as if i have a vacuum leak. my mechanic just installed new intake gaskets- upper and lower. somehow my car is getting a vacuum leak and it is causing it to idle at 1400rpm.

my mechanic said he replaced all the vacuum lines as well. tomorrow he is going to use a smoke machine (like from the dance club) to look for the problem (blow smoke into the cai to find the leak). i have a new iac, and the tps has just been cleaned (by him) i need to get my car to idle like it should say 875rpms or even 1000rpms? it would sound pretty mean with my e-cam and full o/r exhaust. now it just sounds like a pos that has idle issues.

we are almost out of ideas and there are like 5 guys working to solve this problem (not including myself and everyone here on stangnet). he said it drives wicked fast as is but the idle is just really high. he also mentioned that its running a bit rich. he checked in with chris from mass air efi- a distributer in ma. for professional mass air systems (who now owns pro-m). i talked to chris and he said that it is not the mass air and that theres no reason to spend over $300 on something thats not broken- he also told my mechanic that. he suggested some sort of a vacuum leak where unmetered air is getting into my engine causing the higher than normal idle.

look friday, saturday and sunday are the last days of racing here in ma. the new england dragway is done after this weekend and i have been waiting all summer for this. please please please someone help me find out what exactly i need to have done to fix my stang.

-fawcett

1995 gts, 340bhp 302, e-cam, gt40x's, track heat intake, 3/8 spacer, frpp 65mm tb, pro-m 80, pro-m cai, 24lbs, full mallory ignition system (new), aeromotive fpr set around 38-40psi, unequal shorties, o/r h pipe, flows, d&d viper spec t56, alum d/s, brembos all around, cobra r's

 

[CManT1914]

A maf can still cause idle problems, but usually not this drastic. FWIW, a tps can not be cleaned, but the IAC can. I'd test the TPS to see if it's functioning. A Hayne's manual will tell you how to do this. Also, hook up a vacuum gauge to it, don't blow smoke at it trying to find a leak that might not be there. No offense, but your mechanic doesn't sound like he's the sharpest tack in the box.

 

[a50sn95]

I think this is just typical idle issues for a car with the mods you have.
Blowing smoke up the intake will be no more effective than blowing smoke up your arse. I agree with the mechanic eval....
Most people just get some starting fluid, start the engine and then spray the fluid (gas, really, Ether, specifically) at likely sources for vacuum leaks. Any leak will allow the ether into the intake tract and result in a rise in RPM's.
You can get starting fluid at your local CAT, Case, or John Deere dealer. (or any diesel shop).
Have you tried adjusting the idle set screw on the throttle body, or the bypass screw?

Is it idleing at 1400 all the time, or is it doing something else?
Do a search in here for idle issues. lots of folks have them, especially with your level of mods....I did....
Dennis

 

[fawcett]

funny thing (not really b/c its my f-ing car thats broken) my haynes is in my trunk. so it will tell me how to do a tps test? does it also specify how much vacuum pressure my car should have. does it matter if i dont have the original h/c/i combo- mines all different. also, because my intake (trick flow track heat) is rated from 1500-6500rpm (shorter intake height) would that cause some of my idle problems maybe combined with a dying maf? before all of this ***** my car idled at 1000rpm, but it drove kind of crappy. i had my stock intake on this engine at the beginning for like 20 min. the thing detonated like a bastard. i posted plenty of threads on this site-everyone said it would be ok but it wasnt and i found out the hard way.

this guy doesnt seem like a dumbass, i think he knows his stuff. however i dont know why he wouldnt know how/or think to perform a vacuum leak test. if i find out that he didnt do that hes all done. that would be such bs.

if anyone else can help me please chime in
thanks in advance
-fawcett

 

[a50sn95]

The Cam is the biggest issue with your vacuum. All of your mods will change your vacuum, though. I'd think in the 13-15 range should be about right. Mine is around 13, but I think my supercharger pushes a little in at idle, so without I think I'd be closer to 15.
You should get a code for a TPS starting to fail.
I still wonder if the TB screws have been turned...
All of your parts will cause idle issues, I think. Your computer is hardwired for the amount of air it is supposed to see at idle. There are tables for TB airflow, Neutral Idle Airflow, Dashpot Preposition,and Dashpot Decay rate.
These all have airflow values in them for a stock motor.You're not stock,so unless you have a way to change these values, the computer is goingto try to make your car idle with these numbers, which will be all wrong for your car.
I HATED to drive my car in traffic until I got these sorted out in my Tweecer.
Sorry to say, but I think you need a tune....

 

[CManT1914]

Some good points here. An aftermarket cam will cause vacuum to change from stock, which is 19-20. I think you should be around 15, but I could be wrong. You might not get a code for your tps, if it isn't already failed. When my maf went out, it didn't give a code for a while, apparently it was still "in spec" enough to where the computer thought everything was okay. But pull the codes anyway. While your parts will cause idle issues, I don't think you should be idling at 1400. With my stage 1 cam, mine without any tuning idled at 800 or so, it idled crappy, but it didn't idle at freaking 1400.

Sorry to say, but I think you need a tune....

A tune will definitely help driveability issues, so long as you don't have mechanical problems.

 

[a50sn95]

A tune will definitely help driveability issues, so long as you don't have mechanical problems.

I agree. I just can't imagine how big of a leak it would take to increase the idle that much. I'd still like to know if they've backed out the idle screws.
It'd have to be pretty big to do that with the blade completely closed and the Bypass closed, and the ISC closing to adjust for it as well.
And the last time I had a leak like that it WOULDN'T idle. It would keep dying, etc...
Here's a link to an easy spot to check, though...
http://forums.stangnet.com
Codes would be nice to know, too...
Dennis

 

[fawcett]

Update: I didnt like the idea of the smoke trick, but it worked. My mechanic told me that although using a vacuum gauge would tell him if and how much of a vacuum leak there was, it wouldnt tell/show him where it was. He said that after blowing the smoke into my cai, he found it comming out of my EGR. I guess I dont have any reason to get rid of that stuff just yet. Also i dont have a way to tune it out of my computer. i think he said that he was going to work on it but again the EGR is something i am unfamiliar with. if some one would buzz in and educate this young man it would be greatly appreciated!

thanks in advance,
-fawcett

 

[fawcett]

a50sn95: my computers not throwing any codes yet. on another post someone said that they had a bad maf causing poor idle characteristics. the maf however was working well enough to stay within the computers specified limits so no codes would come up.

would my car recognize a leaking EGR and throw a code? i thought it would...
It seems to me as if my mechanic may have the tb missadjusted (iac,tps,tb stopper) as well as this EGR leak.
who here thinks that an EGR leak would cause my car to idle at 1400rpm?
how about combined with a missadjusted throttle body?

im just throwing things out here, this stuffs giving me a headache
-fawcett

 

[WhiteDevil]

In stock for your car should NOT idle at 1000 rpms. Its stock desired idle is 600rpm and is mainly done by the computer. You much have adjusted your throttle body to make it idle that high. I would just play with the throttle body settings to get it to idle correctly.

As for the EGR all there is are two bolts and a paper gasket, fixing that should take all of 5minutes.

 

[CManT1914]

fawcett, EGR is exhaust gas recirculation. It takes relatively cool and fuel richened exhaust gases and sends them back through the motor to be reburned. The cooler temperature of the exhaust as opposed to the combustion chamber temperatures helps cool the combustion temperatures, while the fuel in the gas helps to reduce pinging. This way the computer can cut back fuel, and dial in a bunch of timing to help fuel economy. There is no reason to delete the EGR unless it is broken and easier to remove than repair. It helps fuel economy and is shut off at idle and WOT, so performance is not effected.

FWIW, a leaky EGR can cause a few problems, although I'd still check to make sure that the stop screw is not adjusted too high, and that the TPS reads around .99 volts at idle. Glad he found the problem though!!

JP, his car isn't stock, so he wants his to idle a little higher.

 

[WhiteDevil]

JP, his car isn't stock, so he wants his to idle a little higher.

I understand that now but he said before the mods it idled at 1000rpm, which it shouldnt and it not necessary, it might be now because of the E-cam and all the havoc it wreaks on the stock comp. I would say play with the Tbody and see if that fixes it, then if it does than there you go, Changing the EGR Gasket takes all of 5min and u should just do it anyways.

 

[CManT1914]

I understand that now but he said before the mods it idled at 1000rpm, which it shouldnt and it not necessary, it might be now because of the E-cam and all the havoc it wreaks on the stock comp. I would say play with the Tbody and see if that fixes it, then if it does than there you go, Changing the EGR Gasket takes all of 5min and u should just do it anyways.

Ah! I didn't catch that, lol. Thanks for clarifying it.

 

[fawcett]

ive put over 90 miles on the thing. the idle is starting to come down. stupid me im so used to having mechanical problems i forgot that the computer needs to relearn how to behave. i really think that these miles have made a difference. it has stalled out on me a few times but that was when it tried to idle at like 700rpm when i was turning the wheel. guess i was drawing too much power? ccould this be due to my march pulleys? my stock voltage meter dips down when i turn the wheel.

either way i installed a mgw shifter on my d&d viper spec t56 and its pissa. im going to race the hell out of it tomorrow (hopefully) and sunday for sure.

-fawcett

 

[HISSIN50]

it has stalled out on me a few times but that was when it tried to idle at like 700rpm when i was turning the wheel. guess i was drawing too much power? ccould this be due to my march pulleys? my stock voltage meter dips down when i turn the wheel.


-fawcett

We dont have IAC compensation for PS like 4 bangers do. So with an almost too low idle, U/D's and turning, that is enough (from the sound of it) for you to bog.

 

[CManT1914]

We dont have IAC compensation for PS like 4 bangers do. So with an almost too low idle, U/D's and turning, that is enough (from the sound of it) for you to bog.

Yep, when you turn the wheel all the way, it's common for the motor to bog down a little bit. Then of course you're not gonna be spinning that alternator quite as fast so your volts should drop too.

Yea I'd definitely get some miles on it, but I don't know if the computer will compensate that much. But at LEAST go have some fun with the beast!!