Smog help

[Eric Kropp]

So my trusty little Ranger has high CO and high Hydro-carbons at idle. Seemingly no amount of adjusting the idle/air screws is caring for this matter. The cat appeared good to the eye, with all the honey comb in place and looking like new, it is two years old. The carb is rebuilt and the truck runs real good, actually the best it has in 20 years! Starts great, idles smooth, no hitching, as a rule. I still have not checked out the distributor to see if there is play in it anywhere. This truck has 350,000 miles on the motor and there is a pretty good amount of blow-by. I just wonder if there is to much for the cat to digest.....It does occasionally miss fire at mid rpm bombing down the road, then it seems to disappear. And the next time, it may not mis-fire at mid rpm bombing down the road. I have a friend who has a scope we can put it on and check out the electrics. I did find that the one of the thermactor valves ( the lower one) has a leak in the vaccuum diphram and is likely not operating, but I don't think they are in "play" at the lower rpm's.

Eric

 

[dangerranger83]

One guy on here had this same problem. Turns out he had a rotor explode in his dizzy, happen to P/O, and that caused his missfiring. Also he had the same high emissions stuff that you have. He replaced the CAT and fixed the dizzy problem and passed emissions with flying colors (and he lives in Cali. too).

But with alot of blow by, it might be burning other things to that it shouldnt or not burning efficintly and causing these problems.

 

[85_Ranger4x4]

I had a screw back all the way out and the other came halfway out, the rotor then declared war on the cap... and lost miserably.

Mine had little warning. It cut out once came back, cut out again and with a mighty backfire that blew out my muffler I was dead in the water. It all happened about as fast as it takes me to read that.

No emissions checks or anything here so it might of limped along for awhile with a loose rotor, but it was just as gutless after as it was before.

 

[enginepaul]

Without codes, we are just guessing.
I had hydrocarbons just a little above the limit and changed the oil, cleaned the breather cap with a detergent and replaced the air cleaner at the recommendation of the smog guy and it dropped everything right down.

I'm not near a manual and can't remember which valve dumps air to the atmosphere. One air pump valve puts in air to the cat when the computer tells it to; I'm not positive but that includes idle at times. The air into the cat makes it work better.

 

[Eric Kropp]

I will change the oil and clean the breather and cap. The way mine (the thermactor) is set up the lower valve has the "dump" on it and also has the initial "open", meaning it is an in/out valve controlled by the vaccuum. The upper valve has one in/two outs, and is also controlled by vaccuum. I am real certain that the lower valve is not working because I took it off and put vacuum to it and you can hear it sucking throught the little vent hole. If it is not operating by vaccuum, it is not operating at all as they seem to default to closed. I will grab one of those and install that before I take it to my buddy with the scope and tail pipe anylizer. Are those solenoids on the right fender that control the vaccuum to the egr and thermactor controlled by the TPS?

Eric

 

[enginepaul]

..... Are those solenoids on the right fender that control the vaccuum to the egr and thermactor controlled by the TPS?

Eric

They are controlled by the computer and the TPS is one of the sensors that the computer reads. I'd take a hand vac pump to the junk yard and try a used one.

 

[Eric Kropp]

It's to the junk yard I go....saw some thermactor parts that looked real good to me. Was reading the manual and it mentioned something about 1500 rpm to open the valve.

Eric