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Discussion Starter · #1 ·
Ok guys, the Bronco is doing fine. Trouble here is with my 1993 F-150. Its had a quirk of stumbling after its idled for a while. I cleaned the throttle body. The truck now has no stumble at all. However, the idle has gotten to be too high. Upon early morning startup, at about 70 degrees, it shoots to about 2000 RPM's. Gradually, it comes down, but never makes it to under 1000. Once warmed up, it still idles a bit high unless it sits and idles for a time. Upon putting it into gear, it idles high again ( a lil over 1000 RPM) and wants to take off. The truck never did idle in this manner until after the throttle body was cleaned. Taking a known good part, I replaced the IAC valve. This solved nothing at all. I did extract codes, and there are none present. It almost seems as though the Air charge temp sensor is saying that its ultra cool outside. Though I'm not certain of this being the problem. So here I am asking my panel of knowledge as to where to start to get this fixed. This is my daily driver, and she has got to idle down. BTW, I checked the base idle stop screw and it is clear that it has not been tampered with. I also looked at the butetrfly valves and they appear to be undamaged and are closing and opening properly. Any ideas you guys may have will certainly be appreciated. Thanks. Rick......:thumbup
 

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Im not sure if it is necesary on a 95 but i know on some you have to make sure the tps is back in exactly the right place. If you have it turned some it would make it idle high.
 

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A vacum leak on your intake will cause idle to be high did you take off the throttle body if so did you use a new gasket in reinstall? Cheak all line and hoses to intake and throttle body , what did you clean it with some throttle bodies have a coating and improper cleaning can remove this coating and cause the throttle body to leak air when closed and the leak tells the car to give more gas.
 

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Discussion Starter · #4 ·
i cleaned it with a air intake spray. i did not remove the intake manifold. i checked the tps and its all in specified range w/ smooth flow of voltage. I checked the intake air temp sensor, and it too falls in range. Im beginning to suspect the throttle body has an issue. I cant find any vac. leaks. I ran the koer test and the only code i get is that it cant control engine idle. code 13 i think it was. having checked all these sensors, ran the tests, etc. its really starting to point to a bad throttle body. any extra ideas are certainly welcome
 

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Well bbk makes some nice aftermaket throtle bodies, after I cleaned my throttle body on my vw it ran with a unsteady idle. I searched on the web and found out the computer could'nt sense where the throttle body was. I had to perform throttle body adaption. It was easy disconnect the battery hook it back up turn key to on but don't start after one minute the throttle opened up and then shut all the way. Then the computer knew the position of the throttle. Ive never been through this with my bronco. hope it helps
 

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i have the EXACT same problem on my 91 5.0. i've replaced the IAC, TPS, and cleaned throttle body, intake manifold and plenum. no vacuum leaks, no unnessesary air getting into the engine, just likes to idle higher than normal and jump to 2,000. did you find the problem?
 

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rexf,
did you pull codes?
That is always a good place to start.

A high idle at 2000 rpm is often the TPS. I see that you replaced it, but it may be a faulty part, or the connections may be weak. It is also dependent upon a good ground. Look up how to back probe it and test it in place with a digital volt meter. I have been told by techs MUCH more knowledgeable than I that they really can't be properly tested without a oscilloscope. I'd give it a shot with a DVTM though.

Important grounds are at the left and right upper radiator supports, and near the driver's side hood hinge for the ECU/PCM
 

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Yo,
As advised.
Rolling Idle;
179073

179072

When vacuum leaks are indicated, search out and correct the condition. If the leak exists in an accessory unit, such as the power brake, the unit will not function correctly. Or Air Conditioning when in MAX mode may switch to Defrost.
From my vacuum leak test @ Help with dtc codes and idle

Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19 @ Code Reader
 

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rexf,
did you pull codes?
That is always a good place to start.

A high idle at 2000 rpm is often the TPS. I see that you replaced it, but it may be a faulty part, or the connections may be weak. It is also dependent upon a good ground. Look up how to back probe it and test it in place with a digital volt meter. I have been told by techs MUCH more knowledgeable than I that they really can't be properly tested without a oscilloscope. I'd give it a shot with a DVTM though.

Important grounds are at the left and right upper radiator supports, and near the driver's side hood hinge for the ECU/PCM
I finally found the problem, I advanced the timing and it fixed the problem very easily, I unplugged my IAC and now it works about 93% of the time, I replaced the ignition control module and it completely fixed it.
 
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