High Idle Possible TPS??
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Junior User
Joined: Mar 2003
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From: Virginia
High Idle Possible TPS??
I have searched through the forums and I have similar symptoms as other people. But I just wanted to list my symptoms to see for sure. My 92 302 as of 2 days ago strarted to idle a bit higher than usual(normally 800 rpms, now 1100 rpms). Also its takes it longer to idle back down if I rev it up a bit. I was just wondering from yalls experince if this sounds like the throttle position sensor or could it be a vacumm leak from the upper intake manifold. I checked the idle adjustment screw and no matter how low I adjusted it the idle wouldn't change. also what about is the cost of a new TPS. Yalls input is greatly appreciated. thanks very much
Postmaster
Joined: Mar 2004
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From: Michigan
Your iac is the Idle Air Control motor,and this could be your problem,or a few other things,including your tps,but before you go changing anything,pull the air inlet tube and look to see if the throttle plate is dirty,if so clean it with some carb cleaner,the kind that is safe for o-2 sensors,it will say it right on the can,also disconnect the throttle linkage while it is not running and work the throttle by hand to make sure it is not sticking or gummed up and causing it to return slowly.
Last edited by King Triton; Apr 3, 2004 at 05:05 PM. Reason: cause Im a mechanic not a typist
Elder User
Joined: Mar 2004
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From: Alabama
High Idle
Had a similar problem to this after I had my engine replaced. The vacuum line on the Air Bypass valve came off and the engine idled at about 1100 RPM. Don't know if yours has all the emissions stuff mine does , but if so the Air Bypass Valve is right down by the Smog Pump ( Thermactor Air System) and the vacuum line connects on the bottom of the valve. Put the vacuum line back on and idled at about 700. The Air Bypass Valve on mine was fed by PINK plastic line, which becomes brittle and can break too.
Senior User
Joined: Jan 2004
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From: woodland ca
i just replaced the upper intake manifold gasket on my bronco cause of a vacuum leak causeing my idle to run up to 1500 rpm in park and 1100 rpm in gear and it started out just like yours did at first my engine would evenchally drop down to normal but i ignorded it and it got worse also when i pulled everything apart the throdle was pretty durity so i cleaned it
if i was you i would get out the propane torch and check for vacuum leaks and clean the throdle body
if i was you i would get out the propane torch and check for vacuum leaks and clean the throdle body
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Junior User
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From: Virginia
Thanks for all the replys I checked the throttle body today and it wasnt too dirty at all...Cleaned it up and didn't change anything. I drove it today and it was still idiling high even higher today. I hope to find the problem soon cause this cant be good for the engine specially when its a cold start idle. I will try to check for other things tomorrow. thanks again.
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Junior User
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From: Virginia
I am having a bit of trouble trying to find where the IAC is. Im sure its near the throttle body but if someone could describe to me what it looks like then it would be of great help. Thanks in advance.
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Senior User
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From: woodland ca
i have a 90 bronco w/302 and on my bronco it is located on the thoddle body right under the throddle cabels it is held on by two bolts and has a eletric motor on the back with three wires hooked into it but i would first check for vacuum leaks cause that is more common than that valve going bad best way to check for vacuum leaks is with a propane torch
Elder User
Joined: Mar 2004
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From: Alabama
I just went thru some of this same stuff. Upper intake gasket blew a leak and caused me all kinds of grief. If you can get the good Chilton manual for your year model it has a lot of ways to check some of these components in the chapter on Emmissions. I have a '90 302 and the IAC, also called Idle Speed Control Motor (62.00 at Advanced Auto), is on the driver's side of the throttle body. Bolts on perpendicular to the Throttle Body with (2) small bolts also. You can check the IAC with an ohm meter. On mine the resistance was supposed to be between 7-13 ohms. If not, replace. I checked mine and it was 9.9, but "Leave it to Beaver" I replaced it anyway and it turned out to be my intake gasket. So I shot 62.00 up a wild hogs fanny. If it checks O.K, Iwouldn't replace it. Be sure and the get the best Chilton manual. Usually has a spiffy lookin' front cover.
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Junior User
Joined: Mar 2003
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From: Virginia
well I used a length of tubing to listen for hissing sounds and found my problem at the intake manifold gasket. looks like I will have to replace it. To those who have replaced them on a 302 how hard of a job is this for a typical do-it-yourself person like me? What kind of problems might I face while tackling this job? again thanks for the helpful replys. you guys save me tons of time and money.
Elder User
Joined: Mar 2004
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From: Alabama
Just did mine weekend before last. The one major problem I had was the middle bolt on the passenger side that is up under the manifold. It took a T40 Torx bit x 7-1/2 to 8" long to do this without a whole lot of trouble. Bought mine from Snapon Online for $26.00, but hear maybe Sears or True Value hardware may carry them. Took digital pictures before I started. Memory is not to be relied on for very long. Marked all the vacuum lines coming off the tree on top of the manifold. Cut me about (3) 5/16" x 3" lg. pieces of all thread and screwed them in the lower intake for alignment dowels and the manifold went back on fine. Replaced the throttle body gasket too. Check all those plastic vacuum lines for any cracked or burned places and if yours has an Air Control Valve you might check to make sure everything is intact there. Be sure and hook back up the PCV valve. Other than that it's a piece of cake.
Senior User
Joined: Jan 2004
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From: woodland ca
it took me about 2 1/2 hours to do mine but that was cause i had to search for the
T-40 torx bit that was long enough to get the middle bolt out i found one at the local hardware store the only place in town that the T-40 bit.
Guzzler96 has pretty much expaned the rest so have fun
T-40 torx bit that was long enough to get the middle bolt out i found one at the local hardware store the only place in town that the T-40 bit.
Guzzler96 has pretty much expaned the rest so have fun
Elder User
Joined: Mar 2004
Posts: 537
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From: Alabama
High idle Possible TPS?
The only other thing I thought of on the home today was you might want to torque down your lower manifold bolts while you have the upper manifold off. I couldn't make a livin' at it on the first one, but the second wouldn't be too bad at all.