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89 bronco 5.0 rich

 
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Old 02-25-2011, 09:16 PM
rustee90-150
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89 bronco 5.0 rich

sooooo I got a 89 bronco with 5.0 and i just got it e tested and it barley passed it was extremely high on Hc which is unbernt fuel im pretty sure.. i did a complete tune up on it before i took it in which was plugs , wires cap rotor pcv valve, fuel filer checked the timming and replaced my o2 sensor . so anyways i checked my vacume lines and found a couple that were leaking so fixed them ran a koer test and got the code 42 again so i cleaned my throttle body and iac and rechecked my vacume lines again just to be safe. did another koer test and code 42 came back again.. so i checked the fuel pressure and its okay . theres no exhaust leaks my cats arent plugged either.. so im wondering if i hade a bad air charge sensor could it cause it to run rich and i haven checked my coolent temp sensor either if it was reading off that could cause a rich problem too couldnt it??
 
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Old 02-25-2011, 10:02 PM
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The fuel regulator can supply the proper fuel pressure but it can also have a ruptured internal diaphragm which allows fuel to be drawn in through the vacuum port. Pull the vacuum hose off and inspect it for signs of fuel by smell and a visual test. Cycle the key on/off a few times to see if fuel trickles put that vacuum port.

What do you mean the fuel pressure checked "ok"? What was the pressure at idle? Pressure at idle with the vacuum hose disconnected?
 
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Old 02-25-2011, 11:25 PM
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the pressure was around 35 psi idling and i didnt check it with the line off and theirs no fuel getting through the regulator i did check that.
 
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Old 02-26-2011, 07:05 AM
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I haven't looked up the 2 digit codes...what is code 42?
 
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Old 02-26-2011, 07:49 AM
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Old 02-26-2011, 08:20 AM
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Looks like you are on the right track. The PCM relies on several inputs to meter the fuel/air mixture. TPS, MAP, ECT and ACT as well as the O2 sensor in closed loop. Before blindly replacing parts I suggest checking the output signals on the sensors mentioned above, minus the O2 of course.

Ryan has some great reference material here: Ford Fuel Injection
 
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Old 02-26-2011, 10:55 AM
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ya im going to check the ect and act today there the only ones i havent checked yet soo i really hope one is fubared haha ..
 
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Old 02-26-2011, 02:07 PM
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Before you get too crazy with diagnistics, start with the basics. When I was faced with a similar issue, I found my truck to be slightly low on coolant. This caused the temp sensors to supply false signals to the computer.
 
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Old 02-26-2011, 09:16 PM
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measured the resistance through the ect at room temp with the dvom on the 200 K ohm scale i got 37.5 and 36.5 k ohms for the act so according to the shop manual there both in spec ..
 
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Old 02-27-2011, 07:27 AM
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Originally Posted by Lazy K View Post

I knew how to look up the code and am very familiar with FFI. I was just sayin' I haven't looked up. If the code is KOER code 42 I would think you may have a bad o2 sensor although it's new. "No HEGO switching detected always rich". If the CM code is 42, then it is switching but just rich. If the o2 is bad it will read lean which will in turn cause the eec to add fuel making is rich. I would suggest swapping the o2 again. There are also some tests you can do to make sure the o2 is working and check the o2 ground path.
 
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Old 02-27-2011, 09:10 AM
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Originally Posted by rustee90-150 View Post
measured the resistance through the ect at room temp with the dvom on the 200 K ohm scale i got 37.5 and 36.5 k ohms for the act so according to the shop manual there both in spec ..
Yes they appear to be in specification at room temperature but what do they read near freezing or at operating temperature? I would also suggest checking them in circuit and measure their output voltage.

You also need to measure the MAP sensor. That one will also trigger a rich or lean condition even if it is off a few hertz. Very narrow operating range.

The TPS can be a contributor, but if it is off you usually get an error code or other symptoms such as weird shifting assuming you have an E4OD.
 
 
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