misfiring/rough idle please, any advice?

[rickylee]

Hello,
I am posting here under the name rickylee, but my name is tracy. rick was my husband, who is now deceased. I am asking for any suggestions/advice re: our, my I guess, 1988 ford f-150 2.3liter, 4cyl., 4spark plug, fuel injected truck. It won't pass smog at low rpms, sounds like it's misfiring, and idles rough. I've changed the plugs, wires, cap, and rotor, as well as the air filter. It's smoothed out, but still spews hydrocarbons at low rpms, I still hear a misfire, and the idle is not the smoothest. the engine has many (over 200k) miles on it, so the problem may be mortal. this truck has never been the smoothest idler, but it has always passed smog until now. my husband was a mechanic, and always took care of these things. while he taught me a lot about working on cars, I still relied on him to deal with the tricky stuff. the plugs all have the proper gap, and the firing order is correct, in case you were wondering.
I would really appreciate anything you all might have to tell me. I live in CA.
Thanks!
TR aka Mrs. rickylee

 

[Creager]

Ummm hmmm.. My first thought is compression,

Ignition maybe, plugs are good, wires are good, maybe coil pack? I wish i could tell you how to test this, i know it cant be too hard with a simple volt-meter.

I'd like to see if you can check the compression on all the cylinders, make sure they are all roughly within 10% of lbs of pressure between each other.

If compression is good, im thinking you have a cylinder that may not be firing, allowing raw gas into the exhaust. In that case, ignition could be suspect.

 

[exploded99]

A few ideas:

Yes, probably time to check compression. Not too hard on a 4cyl. I believe there are instructions somewhere on this site if you need them....

High hydrocarbons means unburnt fuel in the exhaust. It may also mean oil in the exhaust as in poor rings or poor valve seals. Oil is just a heavier hydrocarbon. If you have to add more than a quart between oil changes, you may have an issue there.

Otherwise, too much fuel would probably be tired/worn fuel injectors - 200k is a few miles. Another possibilty which happens occasionally is a bad coolant temp sensor sending bad info to the computer and causing the truck to run rich.

There is no easy way to test injectors, so if compression is good, oil consumption is normal, and your coolant temp sensor checks out, then you may than want to find some low mileage injectors to replace yours. There are a few internet sites which sell used ones which are tested and guaranteed.

Don't get in here much ... probably won't be here to read a reply, but someone else should chime in if you need a little more help.

Might want to replace the PCV valve as well... I don't think it will cure the issue, it may help a little tho. Kame sure the hoses are clear.