I have a 89 GT not sure exact mileage odometer says 85k but looks like it has tripped because numbers don't line up perfect. Anyway here is the problem...

When i come to a hard stop with out down shifting my car will turn close to stoping. It also happens when i am down shifting to a slow stop. It doesn't happen every time but 1 time is too many times for me. I was told to check the Mass Air Sensor and Idle Control Valve. So i bought a Mass air sensor and idle control valve off of ebay and installed them this past weekend. Thought it fixed it but guess not. I figure that the parts are good since it is doing the same thing as it was with the other parts installed. So i was thinking it may be timing???? not sure. The car idles fine but when the car shuts off on me and i restart it the RPM's are bobbing from 500-1000, i give it alittle gas and its fine. Any help would be great. This is driving me crazy.

 

check tps voltage

 

tps voltage was 5volts...not sure what it is supposed to be...while checking voltage noticed a HUGE vacume leak on my EGR will that cause this problem?

 

the tps voltage with the throttle closed is supposed to be just under 1.0 volts, like .98-.99 or so. What you probably read was the input voltage to the tps, not the output voltage. probe the green wire from the tps to ground and see what this voltage is.
and yes hugh vacuum leaks will make a engine run badly, so double check all the vacuum hoses for leaks and proper attachement to their fittings. you might also check and clean the IAC which is on the opposite side of the throttle body from the EGR valve as it has a lot to do with the engine idle and how it runs when you lift off the gas too.

 

Hey Stangcrazy, I had the exact same problem with my 86. I ended up finding a vacum line off of the EGR, I actually found this by accident, lucky for me. I also changed out the fuel filter and put some new plugs, I figured it couldnt hurt. But the cause for the stalling was the vacum line to the EGR.

Hopfully you fixed it before my post, just wanted to add some input

 

thanks 86...i fixed the leak and reset the puter just haven't had a chance to check her out yet

 

well i replaced the TPS today and went to check it out and didn't fix it. I was down shifting to a stop and at about 2500 rmp in 2nd gear pushed in clutch and she just died. I went to a hot rod shop today to pick up some exhaust items and they told me to call the mustang "GOD" of Tucson...so i do and he want to charge me $100-120 to bring it in ans put it on some diagnostic machine and there is a chance that it will not stall because it only happens while driving...so there is a good chance that i would be wasting all that money.


also I have a pic of the metal spacer that came with the idle control valve...i didn't install it because there wasn't one on when i took old one off will this effect this problem?

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