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  #1  
Old 06-08-2008, 06:22 PM
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Join Date: Dec 2007
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Vehicle: 1991 ford f150
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91 F150 rough idle HELP

Hey guys,
so heres my problem. I started to notice that my 91 f150 4.9l i6 rwd was running a little rough. So i got the plugs replaced and had the timing adjusted, but still didnt work. SO i took it home and cleaned the throttle body and man was it dirty. Put it back on and its actually worse! esp at 1000rpms the thing will vibrate then be clean, then vibrate again. Now for a 17 yr old truck i dont expect it to be perfect but last year it wasnt having any of this vibration. Its got a 120,000 miles on it and the engine is in mint condition. I was thinking mayby injectors? If that would be the solution how woudl i go about removing the fuel rail and where the hell is the schrader valve???? i coudlnt find it on this.
Thanks!
-Aaron
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  #2  
Old 06-08-2008, 07:41 PM
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If the TB was that dirty, the IAC and MAF are too.........
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  #3  
Old 06-08-2008, 08:23 PM
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The iac is on the tb correct? casue i cleaned that (or what ever else was ontop of it) as for the maf sensor i was under the impression my year didnt have one? if it does where is it?
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  #4  
Old 06-08-2008, 09:15 PM
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Yes, the IAC is on the side of the TB. Remove it and clean it.

Your truck is not MAF.

Also go ahead and pull codes.
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  #5  
Old 06-09-2008, 05:01 PM
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alright good cause i guess i did clean the IAC. I dont have a code reader so i guess ill have to use the check engine light to do it. Anyone ever try it? Im gonna go by the instructions @ www.fordfuelinjection.com and post the codes if anything happens.
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  #6  
Old 06-09-2008, 05:42 PM
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I think the majority of us use that method for pulling codes. Very easy to do, just have your pen & pad ready to go.
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  #7  
Old 06-09-2008, 08:51 PM
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Alright well i got the codes but they confused the **** out of me.....from the KOER test i got 13,11,16,53,85,36,53,21,15? But Im not sure i read them right so i made a video of the codes if anyone wants to see if they can figure it. I also got the KOEO and CM codes but same problem. Also i noticed while the KOER was doing its thing the truck was tripping all over itself?
Here are the videos
KOER- http://www.youtube.com/watch?v=ovNhvCJu6Dc
KOEO/CM- http://www.youtube.com/watch?v=P5dRwW9R26w

THANKS!
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  #8  
Old 06-13-2008, 02:49 PM
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Check to see if you have a vacuum or some sort of intake leak when you cleaned the TB
I was thinking, take the TB back off and install it again to see if you can fins any problems.

Last edited by davis53; 06-15-2008 at 10:12 AM.
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  #9  
Old 06-17-2008, 08:02 PM
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I have been fighting a similar problem, mine hesitates on take off and seems to mis under load at lower >1500 RPMS.

I have checked every thing but compresion and fuel injectors

most of my sensors have been replaced including: EGR, MAP, IAT, and some I can't think of right now. I checked all
Fuel pressure is good.
cats are reemed out and new muffler.

The schrader valve is an electrical switch inside the cab under the dash attached to the firewall to the left of the brake pedal.

I have been considering fuel injectors since I started but not sure how to check. You can check resistance of the selonoids, but if one is bad it should throw a code.

I have not checked mine recently I will need to clear them first and then drive around to generate new ones.
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  #10  
Old 06-17-2008, 08:46 PM
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codes

O.K. dude

you have 3 digit codes
KOEO; 111, 111 no critical codes
stored codes 634 transmission manuel lever position sencor circuit out of self test

(so is mine but I know mine is not adjusted properly)

KOER; 116, 538, 536, 632
116 = ECT (Electronic cooling Temp) out of self test range .3 to 3.7v (this could be the problem)
538 = Insufficient RPM change during KOER dynamic response test/ Operator error (you may have to hit the gas durring diagnostic not sure)
536 = Brake On/Off circuit failure / switch not actuated during KOER test ( I am pretty sure you have to hit the brake durring test)
632 = Overdrive cancel switch not changing state (E4OD) ( and you have to hit this switch as well)

ECT is the only code worth looking at. I have had the same code with same symptoms.

Where is the ECT?
Is it the same sencor as as temp guage?
If temp guage is ok is the ECT ok?
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Old 06-17-2008, 08:46 PM


 
 
 
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