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  #1  
Old 03-06-2011, 02:26 PM
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Default 1994 F-150 5.0 V8 - Losing Power, Rough Idle, Bucking, PLEASE HELP!

Hey everyone,

I'm a newbie to FordForum.....I have a 1994 F150 with about 190,000 miles on it. Its a 5.0 V8 4x4 and its been acting up lately. The truck will start and initially idle around 1000 rpms and be fine, once it warms up it drops way down to around 500 rpms and starts having a real rough idle. Once in gear it will run ok for a while then it will lose power, start to buck/lurch, I'll hear and feel popping from what seems to be under my feet, the CEL will come on, then it will clear itself and kick in like nothing is wrong. It will run ok for a bit then it starts all over again.

About two years ago I had to replace the Idle Airflow, Harmonic Balancer, Distributor & Wires. I'm going to pull codes this coming week and will post them on here to aid in the discussion, but wanted to start the tread to get some ideas about what needs to be done....I've read online that it could be the TPS, a bad O2, a clogged cat, or vacuum issues. The only other clue I have is that it failed an emissions test due to high hydrocarbons.

Thank you all for any and all help!!
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  #2  
Old 03-07-2011, 09:40 AM
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Until you have the codes read, then it's a waste of time to guess what is wrong, and it is no surprise that is failed emmissions, since one of the sensors is inoperative and causing a rich condition.

My guess is that you'll find that it's the Engine Coolant Temperature sensor, but that's just a guess.

There also might be more than one bad sensor.

Not very likely that the TPS is bad. None of the symptoms suggest a bad TPS.

Likewise, cats seldom go bad, unless it's been running rich for a long time.

Get the codes read, and you'll likely have your culprit right away.
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  #3  
Old 03-07-2011, 02:11 PM
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My 92' xlt was doing the same thing and so i thought that my whole firing system went bad. when i bought the truck i replaced the cap and rotor, the wires, the fuel filter, and the air filter. recently i cut the cat off and made a straight pipe from the collector to a glass pack. Nothings worked and im thinking that my injectors are getting clogged or already are clogged a good bit. good luck and let me know what works!
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  #4  
Old 03-07-2011, 02:35 PM
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Usually a high HC reading is caused by an ignition system problem.
Suggest you check/replace the plugs and wires . Don't know how many miles you have on the plugs and wires presently on engine. Cap and rotor also.
It is usually wise to replace the routine maintenance items as part of regular maintenance before condemning any sensors. Let us know how you make out.
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  #5  
Old 03-08-2011, 12:12 AM
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You did replace the plugs and rotor when you did the cap and wires didn't you?

If you didn't, then they almost certainly need to be replaced (make sure you gap the plugs properly), but the symptoms you describe don't sound like fouled plugs.

It'll be interesting to see what the codes say.
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  #6  
Old 03-08-2011, 06:56 AM
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Thank you for the responses so far!!!!

chazzone: yes the plugs and rotor were replaced when the cap and wires were done.

hanky: plugs, wires, cap and rotor have less than 10,000 miles on them.

As soon as I have a chance I will pull the codes and post....can't wait to figure this out and get my truck running right again!
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  #7  
Old 03-08-2011, 04:18 PM
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Hi HC readings are actually fuel going into the cylinders , not getting burned completely and coming out as unburned fuel. You have an ignition system problem could be plug(s), gap , wire problem ,over advanced ign timing even a loose plug wire not on the plug tight. Don't overlook the ign coil. Those are some of the ign causes for high HC readings.
Just because there is only 10,000 mi on the parts doesn't mean they can't be defective.
If you check the firing order, then check your spark plug wire routing , if you have two plug wires next to one another and they are next to one another in the firing order , the wires must be separated so they don't run next to one another.
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  #8  
Old 03-09-2011, 02:53 PM
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One more thing I'd like to check, what kind of plugs did you use? If they aren't Motorcraft or Autolite equivalent, then they could very well be contributing to the issue.

On the other hand, bad plugs seldom, if ever throw codes.

Keep us posted.
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  #9  
Old 03-11-2011, 01:58 PM
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Ok I pulled codes and got the following:

KOEO:
111

CM:
172
173

KOER:
536
632

Not sure what to make of these...please let me know thoughts of what needs to be checked to get my baby runnin right!! Thanks again for everyone's input so far!
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  #10  
Old 09-07-2012, 03:21 PM
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It appears I have a similar problem with my truck. What was the problem with your truck? Any advice would help.
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Old 09-07-2012, 03:21 PM
 
 
 
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1994, 250, 50, 94, bucking, driving, e250, econline, f150, fine, ford, hc, high, idle, idles, rough

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