Throttle Body Sensor?
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Throttle Body Sensor?
Hi, I have a 1996 f250 with a 351. Auto. The last few days when i complete stop the truck starts to die but picks itself back up to normal idle. It will occasionaly die. I've checked both pumps, Changed the fuel filter, air filter, oil, and transmission fluid. Obviously the last two had nothing to do with the problem. Could this be a sensor of some kind? I'm not getting a check engine light so i dont think that there would be a code. I'm stumped any tips would be appreciated i'm only 17 and dont have the money to fix it right now. with it being my only vehicle anything would be nice 
If it helps its running normal other than almost dying/dying when i COMPLETE stop.
Thank You,
Craig.
If it helps its running normal other than almost dying/dying when i COMPLETE stop.Thank You,
Craig.
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Joined: Jul 2004
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From: Northwest Germany
Sounds to me like a bad idle-air-valve IAV. It is fitted to the throttle body. Some use carb cleaner to clean it or just replace it. But before you start, do a search for IAV related postings in this forum. Gives you a better idea what symtoms are caused by a bad IAV.
Good Luck
Good Luck
Lead Driver
Joined: Feb 2003
Posts: 8,140
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From: Oak Harbor, OH
Pull the codes, some won't set the light.
If it's a bad IAC (Idle air control) then it won't be intermittent. The TPS will go out and act like the IAC so you wind up replacing $120 in parts instead fo $35 or so.. Start with this simple test. With the truck in park, at idle, pull the connector off the IAC (located on the right side, as you look at it, of the throttle body). If the truck idle changes then it's working. If it doesn't rev the engine with it unhooked, upon returning to idle it should die. If it doesn't then the IAC is probably bad. The TPS (throttle position sensor) is a little trickier, it's mounted to the bottom of the throttle body. To test it get a DIGITAL multimeter. Set it to DC volts, turn the key on ( DO NOT START), and use the red (+) lead to probe the CENTER wire, and the black (-) lead to probe the black wire. You should have .7 ~ .9 volts, move the throttle through the entire range and the higer en voltage should be about 4.5 volts with no hiccups in between.
If it's a bad IAC (Idle air control) then it won't be intermittent. The TPS will go out and act like the IAC so you wind up replacing $120 in parts instead fo $35 or so.. Start with this simple test. With the truck in park, at idle, pull the connector off the IAC (located on the right side, as you look at it, of the throttle body). If the truck idle changes then it's working. If it doesn't rev the engine with it unhooked, upon returning to idle it should die. If it doesn't then the IAC is probably bad. The TPS (throttle position sensor) is a little trickier, it's mounted to the bottom of the throttle body. To test it get a DIGITAL multimeter. Set it to DC volts, turn the key on ( DO NOT START), and use the red (+) lead to probe the CENTER wire, and the black (-) lead to probe the black wire. You should have .7 ~ .9 volts, move the throttle through the entire range and the higer en voltage should be about 4.5 volts with no hiccups in between.
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Ok I went out this morning with the truck running and pulled the connector. The truck idle dropped to around 400 rpm. But it was consistent. I reved it and it dropped down and stayed at 400 rpm.
I dont have a voltage meter any other way on the other sensor?
I dont have a voltage meter any other way on the other sensor?
Post Fiend
Joined: Mar 2002
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From: Bonita Springs FL
Here's what I would do. Actually, did. I had similar problems and this cleared everything up. All you need is a stiff brush and a couple cans of brake cleaner. OK, and a throttle body gasket.
Take the throttle body off completely. Take the TPS and the IACV off. Clean the IACV out throughly with the cleaner. Spray it out until you're sure that you got it as clean as you can get it. Do the same with the throttle body with the help of the stiff brush. Put everything back together. Your truck will start and idle 100 times better. You didn't say how many miles you have, but I did this on our Bronco with 120k on it, and it idles like new.
Take the throttle body off completely. Take the TPS and the IACV off. Clean the IACV out throughly with the cleaner. Spray it out until you're sure that you got it as clean as you can get it. Do the same with the throttle body with the help of the stiff brush. Put everything back together. Your truck will start and idle 100 times better. You didn't say how many miles you have, but I did this on our Bronco with 120k on it, and it idles like new.
Lead Driver
Joined: Feb 2003
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From: Oak Harbor, OH
Originally Posted by 96f250xl351
Ok I went out this morning with the truck running and pulled the connector. The truck idle dropped to around 400 rpm. But it was consistent. I reved it and it dropped down and stayed at 400 rpm.
I dont have a voltage meter any other way on the other sensor?
I dont have a voltage meter any other way on the other sensor?
Post Fiend
Joined: Mar 2002
Posts: 19,402
Likes: 38
From: Bonita Springs FL
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Ok i'm going to go get a digital multimeter and test it. And i'll clean up the throttle body and let you know... if anything else comes to mind any input will help. The truck has 256,000 on it. It was a company truck and i have all the maintanence records it was very well maintained.
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Ok i'll see if autozone can have them read for me, but i'm not getting a check engine light is that a problem? So while i was out driving today i noticed that if i brake hard rather than slowly stop it doesnt hesitate until i give it gas... if that helps
~Craig~
~Craig~
Post Fiend
Joined: Mar 2002
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From: Bonita Springs FL
Your F-250 should still be OBD-I, so you can read them with a paperclip. See www.fordfuelinjection.com. I wouldn't trust the idiots at autozone to read a stop sign.
With the braking thing you mention, it could be a vacuum leak. Start the truck and then shut it off. In an hour or so, pull one of the vacuum lines off one of the coffee cans. You should hear it hiss. If not, you may have a vacuum leak.
With the braking thing you mention, it could be a vacuum leak. Start the truck and then shut it off. In an hour or so, pull one of the vacuum lines off one of the coffee cans. You should hear it hiss. If not, you may have a vacuum leak.
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ok i went out and pulled one of the vacuum lines off of the throttle body.. No hissing sound what so ever. I notice when i shut the truck off it sounds like its losing air somewhere *hissing sound* the truck is only stalling around 1-5 mph and its mostly when i'm holding the truck back with the brakes
Post Fiend
Joined: Mar 2002
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From: Bonita Springs FL
It could be the booster itself, too. They can leak internally and be the cause of the vacuum leak and bad idle. If you have a vacuum pump, you can see if it holds vacuum. If not, time for a new one.
Also, a vacuum line off the throttle body? How sure are you that it's a vacuum line? The only lines there that I can think of off the top of my head are the coolant lines.
Also, a vacuum line off the throttle body? How sure are you that it's a vacuum line? The only lines there that I can think of off the top of my head are the coolant lines.