Code 31 and 22??

Asked by May 01, 2017 at 01:56 AM about the 1988 Ford F-150 XL Standard Cab 4WD LB

Question type: Maintenance & Repair

Ok I've got a really annoying problem that I just
can't figure out. I have a 1988 ford f150 and have
been getting codes 31 and 22. We took it through
emissions and it failed horribly. So we got an obd1
ran the codes and replaced the egr sensor and
map sensor we'll also got a new O2 sensor and a
new egr valve. We replaced the sparkplugs got a
new fuel pump and filter checked all the lines to
make sure there was no vacume leak and when we
were all done the truck ran smooth. We took it
through emissions and it passed with flying
colored the truck ran like a dream then about three
days ago the check engine light came back on and
it started running rough again and the same 2
codes are popping back up the we replaced the
whole system and its still reading the codes we
even checked the new parts to make sure they
weren't defected. Now here's the part that's
messing with us we went outside to turn it on this
morning and the light was off the truck was
running smooth we drove it all day with no
problems went to turn it off . a few minutes later
we turn it back on and the truck started running
rough again the check engine light back on and
the same 2 codes popped back up. I have no idea
what else to do. The last thing I can think of is
carbon build up but I'm not sure. Is there anyone
who might know what the problem is your
suggestions would be very helpful at this point.
Also sorry for the long message.

6 Answers


Those were noted for getting carbon pieces in the EGR valve blocking it open, there is a screen that you can get at your local parts store that replaces the EGR gasket, and they do help on badly carboned up engines, the other thing is make sure all the sensor grounds are good and you don't have an internally broken wire for that system, Fords wiggle test can prove this theory out. HTH

Thanks we are going to clean the carbon out the best we can. Hopefully this will help. I'll keep it updated.

OK I've got an update on the truck we did some more checking and looking at the wires as well and noticed that one of the connectors wasn't going in and connecting all the way. It was the connector that attatches to the pcv sensor. It was going in but with the vibrations of the engine it was falling out we hooked up the obd1 our code 31 is gone its just reading code 34 and 22 we went out and got a new connector for it. And it made the check engine light go off. We drove it around nothing wrong went to a friends house to break a few bottles open and celebrate this battle that we've been having and went to turn the engine on to see that low and behold it came back on the obd1 is still reading 34 and it went back to rough ideling. Any suggestions out there? This is becoming a serious headache.


Did it get some more carbon in the EGR valve? You may also want to check the actual reading on the EGR valve sensor, I've had some after markets show the valve was open slightly when it wasn't, so it was setting the check engine light, on those units I went with a Ford factory sensor.

I'll take a look and see If this is the problem I'll make sure to keep this updated.

Ok here's an update on the Ford. So we did check to make sure the aftermarket parts were compatible and checked to see if the egr valve was doing its job correctly. Everything on it was checking out just fine. We cleaned some more carbon out and we had a friend wonder if it was the catalytic converter. I don't think that would be the case since when we ran it through the emissions it passed with flying colors. Plus's it hasn't been burning any bluish white smoke out the exhaust. So we did a little more tinkering and my friend undid the coal filter he took it to work cleaned it out by the way there was a lot of debris in this sucker. We put it back on and the check engine light went off. Its been off for the past couple of days now and we haven't had any problems since. No CE light no rough idle no rich fuel or anything. I think that with the coal filter being clogged it wasn't being able to breath the fumes out properly so it was like it was choking. Anyways now that its been cleaned its been running a heck of a lot better. Here's a picture of the debris that came out of the coal canister.

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