Need help

Ask technical questions about your Ford Bronco II here. Technical write-ups on your axle swaps, engine swaps, chop tops, etc. are encouraged.
martyanderson10
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Joined: Sat May 04, 2013 6:19 pm
Location: TN

Need help

Postby martyanderson10 » Mon May 13, 2013 8:01 pm

My 87 Bronco ii is having some issues. When I am driving sometimes it starts to miss and runs rough and when I give it gas it takes right off and runs strong. It is very inconsistent in when it does it. I put it on OBD1 scanner and it came up EGR valve. The cats are gutted and there are no O2 sensors on it. I removed the egr valve and cleaned it up and it seemed to be working properly, then I drove it and thought I had it fixed. it ran great at all rpm for several miles then started cutting out and when I accelrated it takes right off. Does this sound like a bad egr and if so should I just delete it and put a plate over the egr mounting hole? The only other thing I can thionk of is a fuel problem (filter/pump). Any ideas would bve appreciatted. thanks

Yeti
Posts: 8
Joined: Sun Oct 06, 2013 1:50 am
Location: NC

Re: Need help

Postby Yeti » Fri Oct 11, 2013 5:15 pm

My gas filler neck had a crack and was letting dirt get inside the gas tank when the tires spin. That caused all sorts of problems...filter, fuel injector ect....

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tekatlarge
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Joined: Tue Jan 17, 2006 8:54 am
Location: Kent, Worshington

Re: Need help

Postby tekatlarge » Sat Oct 12, 2013 11:27 am

Is that engine a 2.9L? I believe it should be. First thing I want to say is Why did you remove the oxygen sensors? The sensors are needed for the engine computer. If you have an oxygen sensor aft of the Cats and you gutted the cats or removed the sensor your engine won't run right. Gutting you cat converters does NOTHING for horsepower. It is also a Federal Crime if you put that vehicle on the street. I would wonder why you would gut the cats. did you test them to ensure there bad before gutting them.
I am not trying to beat you up but I see this everyday. People wanting to improve the performance but not really understanding what their doing. Try undoing what you have done and see where you are and go from there!
The Tek @ Large
Kent,Worshington
I was borne under a rock. So what's your excuse?

Yeti
Posts: 8
Joined: Sun Oct 06, 2013 1:50 am
Location: NC

Re: Need help

Postby Yeti » Sun Oct 13, 2013 5:40 am

I agree that you need O2 sensors. They tell your computer when the engine is warm so it then adjust the fuel mixture. Your gas mileage will improve with O2 sensors.

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tekatlarge
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Location: Kent, Worshington

Re: Need help

Postby tekatlarge » Sun Oct 13, 2013 11:24 am

Yeti wrote:I agree that you need O2 sensors. They tell your computer when the engine is warm so it then adjust the fuel mixture. Your gas mileage will improve with O2 sensors.



I have to respectfully disagree. The O2 does not tell the computer if the engine is warm or not. The temperature sensors mounted on the intake senses water temperature and sends that info for the computer. All the Oxygen sensor does is tell the computer if the engine is running rich or lean by measuring the amount of Oxygen in the exhaust gas.

Oxygen sensors usually and I say usually work in what is called closed loop. Closed loop means the engine is operating under temperature and or at an Idle. When the engine is warm and running under load the computer goes into open loop which means the computer relies on the internal mapping tables and input from speed sensors,Map or MAF sensors and air inlet temp.

If you want to learn more check out my website and look in the automotive Technical Library.
The Tek @ Large
Kent,Worshington
I was borne under a rock. So what's your excuse?

Yeti
Posts: 8
Joined: Sun Oct 06, 2013 1:50 am
Location: NC

Re: Need help

Postby Yeti » Sun Oct 13, 2013 2:47 pm

So if the o2 sensors are not hooked up the engine still thinks its in closed loop/cold even when its warm correct ? Thus dumping more fuel than is needed ?

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tekatlarge
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Location: Kent, Worshington

Re: Need help

Postby tekatlarge » Sun Oct 13, 2013 9:18 pm

If the Oxygen sensors are gone the computer should go into "Limp Mode" Which means it switches to a different fuel table and the mixture is basically set in a fixed amount and will not change due to changes in load temp or speed. This could very well dump more fuel than is needed and as a result the mixture goes over rich. Yes it would make your mileage really suck, Let alone drive ability would suck!

When something like the above happens and not corrected could poison the cats as an extremely rich mixture will not burn off and deposits clog the converters. Of course No Cat No Damage.
The Tek @ Large
Kent,Worshington
I was borne under a rock. So what's your excuse?

kirkland2887
Posts: 86
Joined: Sun Jan 29, 2012 6:00 pm
Location: Albion, Idaho

Re: Need help

Postby kirkland2887 » Tue Oct 15, 2013 6:38 pm

K. Time to clear up the o2 sensor knowledge. The oxygen sensor measures the amount of oxygen in the exhaust. This tells the pcm wether you are running rich or lean. This information is use d for optimum fuel economy and will not make your truck do what you are describing unless it is bad and the sensor is reading full lean. When you first start the vehicle the motor runs on info from temp, iat, map/maf sensors. This is open loop. When the o2 sensor reaches 600 degrees it starts switching. This is called closed loop. The sensor works on a range from 0-1v. 0 is lean , and 1v is rich. Perfect fuel mixture is .5v. You can use a voltmeter to monitor but it has to be a good one as the switching is constantly bouncing between .1-.9v. Even some lower end fluke meters are not good enough. Taking the oxygen sensor out of the equation just puts you back in open loop. This will not make the truck run shitty. May effect mileage a little but not enough to matter. I believe the 2.9 uses a single wire self generating voltage sensor. If it a four wire sensor then it has an internal heater to shorten open loop time for emissions. The oxygen sensor is for emissions only. Will not effect drivability unless sensor is constantly reading lean or rich. If the computer sees that it is not responding correctly according to other sensor info, it will quit reading o2 and turn on check engine light.

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wilsonsuarez
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Joined: Mon Dec 16, 2013 10:11 am
Location: Miami, Florida

Re: Need help

Postby wilsonsuarez » Fri Dec 20, 2013 4:58 am

i dont know much, but i know a bad Idle Air Control valve or Mass Air sensor will make it run like crap until you mash the gas and gives of the illusion of running right. also, vacuum leaks will make it run like crap too. i saw you put that it doesnt happen all the time, when does it happen most? narrow your search, i seem to struggle with that myself!!!


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