5.0 Fast Idle? Help!
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5.0 Fast Idle? Help!
94' Bronco, 5.0 w/E4OD. Idling very high in park (1200 to 1500rpm). Shifts hard when I put her in gear.
My Haynes manual indicates several sensors that could be the culprit. I dont have the capability to pull codes without going to shop. Is this something any of you have experienced before? Is there a most probable sensor?
Please advise!
Thanks,
My Haynes manual indicates several sensors that could be the culprit. I dont have the capability to pull codes without going to shop. Is this something any of you have experienced before? Is there a most probable sensor?
Please advise!
Thanks,
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From: Auburn/ Opelika
A lot guys including myself have had problems with the IAC lately. (Idle Air Control) It's on the side of the throttle body, it's a cylinder with a flat side where it bolts up to the tb. It has a sensor on it. A good way to test if it is the culprit is to start it and unplug that sensor, if it idles normal then thats the problem. Means it's faulty cause it's not telling engine what to do. Worked on mine anyways. -William
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From: Marquette/ Traverse City
my 90 use to idle at around 2300 rpms in park, and problby 1600 in drive. it came like that, not exactly sure why it did it, i just took it in to get it fixed. it was kinda cool thoug, it would idle at 27 mph. kind of made parking in icy parking lots fun though, back tires never seemed to wanna stop, but thats cause i had brake issues
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Is this when you first start up your truck??? If the weather changes and you are located in a cold climate your baro sensor will indicate a change in weather and the computer will warm your motor up longer at around 1500 rpms. Min is the same as yours and it warms up on a 32 degree for 5 mins. at 1500 and then kicks down to 850 +/- rpms. If this is not the case check your Idle air control valve assembly...it may be caked up with carbon from the egr valve being direclty across from it on your throttle body.
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My idle was almost the same as yours, It was upper intake manifold gasket leaking in air which makes the computer think your giving it some throttle so it gives it gas to compensate so you get a high idle. I would check the other problems first the TPS and the Idle control valve then of couse vacuum leak. If not those then sucking in from EGR or manifold gasket or throttle body gasket.
89 Bronco 302
89 Bronco 302
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Yeah! Upper/lower intake leak. Use a 24" long peice of rubber hose, stick up to your ear and listen around the intake. You will deffinately hear it, it'll sound like air getting sucked out of the hose.
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From: Auburn/ Opelika
So after replacing the IAC and you still get a high idle, there is a possible leak? I replaced the IAC and on start up it still kicks up to 1,000 rpm and holds til you give it some gas. How difficult is it to replace the upper and lower intake gaskets? Can this problem be associated to a loud, plastic sounding ticking noise? It's consistent and has always done it. -William
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From: Running Springs CA
Originally posted by broncobillybob
A lot guys including myself have had problems with the IAC lately. (Idle Air Control) It's on the side of the throttle body, it's a cylinder with a flat side where it bolts up to the tb. It has a sensor on it. A good way to test if it is the culprit is to start it and unplug that sensor, if it idles normal then thats the problem. Means it's faulty cause it's not telling engine what to do. Worked on mine anyways. -William
A lot guys including myself have had problems with the IAC lately. (Idle Air Control) It's on the side of the throttle body, it's a cylinder with a flat side where it bolts up to the tb. It has a sensor on it. A good way to test if it is the culprit is to start it and unplug that sensor, if it idles normal then thats the problem. Means it's faulty cause it's not telling engine what to do. Worked on mine anyways. -William
I have the the problem of the engine "racing" right after it starts. Hot or cold, the rpms surge way up, with the CHECK ENGNE light blinking, and then settles down. No codes are stored in the computer. After it settles down, the idle is rock steady.
Jim
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Update
Okay gang, tonight I disconnected the the Idle air Control connector and noticed a drop in rpm ( note that the air supply snorle was also separated from the throttle body). When I connected the snorkle with the IAC disconnected the rpm's went back up. I removed, inspected and cleaned the IAC valve (not very dirty). Re-installed the valve and snorkle with no noticable improvement to idle.
My temporary fix was to back out idle adjustment screwto 900-1000 rpm.
I guess my next step will be to buy a multimeter perform the diagnotic checks per my Haynes manual on the TPS, and then move on to the next possible sensor.
Any other ideas?
Thanks,
Nothing better to do!
My temporary fix was to back out idle adjustment screwto 900-1000 rpm.
I guess my next step will be to buy a multimeter perform the diagnotic checks per my Haynes manual on the TPS, and then move on to the next possible sensor.
Any other ideas?
Thanks,
Nothing better to do!
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I agree with sinjin90 and Artistictouch that your problem could be a vacuum leak. Mine did the same thing and it was the lower intake manifold gasket.
You can either check with a piece of vacuum hose as described above, or CAREFULLY spray some carb cleaner around the gasket area with the engine running. If the RPMs pick up even more, it means that the carb cleaner is being sucked in - and you found your leak.
Good luck.
You can either check with a piece of vacuum hose as described above, or CAREFULLY spray some carb cleaner around the gasket area with the engine running. If the RPMs pick up even more, it means that the carb cleaner is being sucked in - and you found your leak.
Good luck.
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I closed off all air coming in through the throat plates and it still ran around 1000!! So figured had to be geting in air somewhere i finally gave up could not find it. I Tried the spaying throttle body cleaner around looking for a increase in idle to find the leak, even tried propane as others had suggested on these forums. Finally broke down and took it to shop they put smoke in it somehow and found the upper intake gasket leaking. THey told me it was completly gone pretty much, that is why it idled at 1700. Runs like a new one now. I just put a heater core in last Saturday and made some new Taylor Plug wires( used to work there hint hint)
everything in doing well.
89 KC Bronco
everything in doing well.
89 KC Bronco
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From: Chicora
Okay, I had a problem with this before in my 88 F-150 with a 5.0. I tried everything, but could not get it to idle correctly, and it was getting out of control. One night my friend and I were looking at the engine and my friend just happened to notice the gasket slightly purging out between the upper and lower intake manifold. I changed the gasket the next day and it fixed the problem.
The old gasket was all cracked and falling apart.
The old gasket was all cracked and falling apart.
