1991 Ford F-150 Truck Failed Emissions

Tiny
BUDATATTOO
  • MEMBER
  • 1991 FORD F-150
  • V8
  • 2WD
  • AUTOMATIC
  • 490,000 MILES
I recently bought an old F150 with the 4.8L motor. I took the truck to emissions and it passed everything except hydrocarbons in idle. The truck is running real rich because there is a strong gas odor. The limit is 220 and mine is 1235. Is it a faulty oxygen sensor? I just replaced the water pump, plugs and wires, and cap and rotor. The truck runs solid but rough. I am a single mom and have no clue where to start. I took it to Meineke and they said it was the EGR but they also charged me for work they never performed. Rip offs! Could it be the EGR? Any help would really be appreciated. Thanks!
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Saturday, March 13th, 2010 AT 1:02 PM

22 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Does it actually have that many miles?
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Saturday, March 13th, 2010 AT 4:54 PM
Tiny
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It has a little over 482,000 according to my odometer! But do you know anything about why the hydrocarbons are so high in idle so I can get it to pass?
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Saturday, March 13th, 2010 AT 8:25 PM
Tiny
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  • EXPERT
I needed to know if the mileage was correct. Chances are (with that many miles) the compression in the engine is getting weak and all of the fuel isn't getting burned. I would start with checking compression to make sure it is within spec. If it is, then we need to check O2 sensors.

Let me know if you need directions for checking compression.

Joe
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Saturday, March 13th, 2010 AT 10:06 PM
Tiny
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I didn't until I busted out my haynes manual for my broke down car. That is another story. I don't have a compression gauge and that's a problem if they are expensive. I know I have a valve cover leak on the drivers side that's pretty bad and I'm going to try to tighten it down in the morning. I actually bought new valve cover gaskets but now that I have to drive the truck everyday I don't have enough time to take all that intake apart. Am I correct that there are three oxygen sensors on the truck and they all are the same? I was thinking I could get a sensor and try it in each one to see if it works? Then hopefully return it if it's not my problem.
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Saturday, March 13th, 2010 AT 11:17 PM
Tiny
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  • EXPERT
As far as the compression gauge, most nationally recognized parts stores will lend them to you for free. Basically, when you get it, you pay them for the tool. WHen you return it, they give the money back. As far as the O2 sensors, you could give it a try to see if it helps.

Let me know if you have other questions.

Joe
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Sunday, March 14th, 2010 AT 4:40 PM
Tiny
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Hi Joe,

I called autozone this morning and it's 38 bucks to rent a gauge so I am going to go get it and a sensor this weekend. Hopefully the sensor works:) I'm thinking if the compression is bad it's probably the valves because of the oil leak. Wish me luck and thanks!

Joyce
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Monday, March 15th, 2010 AT 7:26 PM
Tiny
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  • EXPERT
Joyce:
THey should refund the money when you return it. If they don't, you can buy one for that amount.

I will be checking my email all weekend, so if you have questions or concerns, let me know and I'll do my best to help.

Joe
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Monday, March 15th, 2010 AT 9:03 PM
Tiny
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Hi Joe,

I tightened up the valve cover, replaced the O2 sensor and dropped sum lucas in the tank. I did not do a compression test for the shear fact that even if the compression has gotten weak there is nothing I am able to do about it at this time. Valve jobs are not within my capabilities when I have to drive it every day. I am going to attempt one final thing and that is the EGR because it was another code that showed up. Wish me luck and thanks for everything.

Joyce
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Saturday, March 20th, 2010 AT 9:47 PM
Tiny
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  • EXPERT
Joyce:
WHen you remove it, chances are there will be carbon built up in both the egr and the intake. Make sure to clean it. After cleaning, check to make sure the valve is opening and closing properly.

Let me know what you find or if you have other questions, and GOOD LUCK.

Joe
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Saturday, March 20th, 2010 AT 11:33 PM
Tiny
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Joe,

Is there anything in particular I should use to clean them out? Someone told me rubbing alcohol. Is that correct? My engine has some surging, so I'm hoping cleaning/replacing the egr is what is needed. I also have two skinny little intake lines (one red, one black) that have been cut off but are supposed to go to a "can" on the passenger side. Could this be a possibility for the truck failing emissions? I'm racking my brain trying to find a solution. As always any help is appreciated.

Thanks,
Joyce
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Sunday, March 21st, 2010 AT 12:12 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
I think you are refering to the charcoal canister. THere should be lines going to them. It collects fumes from the fuel tank and they get burnt through the intake. So to answer your question, yes it could cause an emission problem.

As far as the carbon, it is usually really hard. You will most likely end up chipping it away. However, I use brake cleaner once I get the majority out. It cleans good and evaporates really fast too. Just make sure you are in a well ventilated area. It stinks!

Joe
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Sunday, March 21st, 2010 AT 12:38 AM
Tiny
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Hi Joe,
It's the damndest thing but I passed emissions today! Don't get me wrong I'm grateful but if I knew how I did it then I could correct what is still wrong. So let me start from the beginning and maybe you can help me! I took the truck to emissions the first time and my loaded hydrocarbons were 115/220 and my hydrocarbons in idle were 1235/220. My CO in idle was.44/1.20 and loaded was.03/1.20. I replaced the water pump, plugs and wires, o2 sensor, cap and rotor. I also ran a 3-step fuel/intake system cleaner threw it yesterday foregoing the egr until I had it put on a diagnostic, and sprayed a little intake cleaner in the egr. By the way, when they ran it on the obd 1 diagnostic the only code they pulled was 67 and not an emisssions related code. Today I replaced to skinny vacumn lines going to the charcoal filter and had ran good gas in it for a couple of days.

Anyhow, this is what I would like to know. Today when they tested it my hydrocarbons in idle were 166/220 but my hydrocarbons loaded were 219/220. What is going on? I'm thinking the hoses were cut to pass hydrocarbons in idle once upon a time but why are they barely passing loaded now? I am going to do my homework to the best of my ability but any foresight would be helpful. Emissions will happen again!

Thanks,
Joyce

Anyhow, this is my
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Monday, March 29th, 2010 AT 8:14 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Chances are the hoses and all the other things you did caused it to pass. A good tune up can do wonders.
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Monday, March 29th, 2010 AT 11:26 PM
Tiny
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Joe,
I'm glad all my hard work was not in vain but I am concerned about the HC's still being so high under load because I barely made it. I did some checking and came up with this list of possible causes:

Elevated HC readings during acceleration indicate ignition misfire under load. The causes could be:

Defective knock sensor;

Weak ignition coil(s);

Excessive resistance in spark plug wires;

Arcing inside the distributor cap;

Worn, fouled or incorrectly gapped spark plugs;

Over-advanced ignition timing; or

Lean air/fuel mixture.

If you have anything to add please let me know.

Joyce
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Tuesday, March 30th, 2010 AT 7:58 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Joyce:
Any of them could cause it. Some are tied together. For example, a bad knock sensor will affect the timing. Is the engine missing?
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Thursday, April 1st, 2010 AT 7:24 AM
Tiny
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  • MEMBER
Joe,
I haven't noticed any misfire but what I have noticed is the timing does seem really high. I also noticed that I need a fan clutch because the fan is moving real slow. I need a new drive belt because it's got a bunch of little cracks and it bogs down when I get on the gas. I'm thinking fuel filters because I've run a ton of injector cleaner threw it and hoping it's not the pump. The motor seems to jump around a lot too, so I am going to check the mounts. I'm going to try to work on the fan and serpentine this weekend but I have a lot to do before Easter.

Happy Easter,
Joyce
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Thursday, April 1st, 2010 AT 8:52 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Joyce,
Let me know when you get started. We're the same here with Easter. The fan clutch can be a pain so let me know when you replace it. I have a little trick to get it off. The special tools they make for them are junk.

Let me know when you're ready.

Joe
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Thursday, April 1st, 2010 AT 11:08 PM
Tiny
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Hi Joe,
Hope your Easter was good. I went today and bought the fan clutch for the truck but I'm not going to mess with it until I'm off on Saturday. I bought a truck for parts this past weekend but the motor was different and so was the clutch. I got lots of other great parts I need to put on though! Anyhow, I've been reading up on the fan clutch and a lot of people have said that the rental crap to get it off at Autozone is junk. So if you have any great ideas to make my life easier I would be happy. Also, if you have a recommendation on a reasonable sized compressor to run air tools that would be great because my elbows get to killing me:)

Thanks,
Joyce
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Tuesday, April 6th, 2010 AT 10:19 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
You will laugh at me if I tell you how I remove them. I take a large cresent wrench, wedge something behind the waterpump pulley, and smack the wrench a few times with a dead blow hammar. It usually takes a few hits, but the nut will come loose. Also, don't remove the belt. It will help prevent the waterpump from turning.

As far as a compressor, at my house I have a small one. If I recall, it has a 20 gallon tank and is 5hp (electric). It keeps up with my tools really well.

Let me know how it goes and no laughing at my method. I can't believe I posted it on the internet. Now everyone will think I'm a hack at my job. (LOL).

Take care,
Joe
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Tuesday, April 6th, 2010 AT 10:58 PM
Tiny
BUDATATTOO
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You know what they say about he who laughs last! Necessity is the mother of invention and I'm not laughing if it works! I'm going to look into a small compressor like what you have because it will definitely make my life easier. I will let you know how it goes Saturday and thanks!

Joyce
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Wednesday, April 7th, 2010 AT 8:06 PM

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