Help with codes

[01PONY]

Hi. I am getting 3 codes on my kids '91 LX 4 cyl. Code 172, 186 and 334.

172
(R,M)
Oxygen sensor not switching - system is or was lean - Single, Right or Rear HO2S - Fuel control

186
(M)
Injector pulse width longer than expected or Mass Air Flow (MAF) lower than expected - Fuel control

334
(O,R,M)
EVP sensor is/was high - EVR

I'm not sure what the fix is. The CEL comes on at times and I beleive these are all memory codes. I get a 111 in the first round. Any help is greatrly appreciated. Thanks...

 

[Delray Dude]

1st thing I'd try is the O2 sensor. If it went south then it will throw off the computer. I have an Air / Fuel guage in my car and when I had a sensor go bad (or slow) it would throw the CEL on sometimes. If the computer doesn't see a swift sweeping range from almost 0 to 1 volt back and forth during a normal condition (Idle or constant cruising) it'll freak out and throw the CEL. I've seen O2 sensors work, then respond slow, then stop, then start working again all in the range of a few minutes. As the O2 sensor gets older it slows down its pulse and the computer doesn't like it.
Also, you can reset the computer but disconnecting the battery for 10 to 15 minutes and let the computer reset itself - sometimes that will work.

Also unplug the connectors at the computer, MAF and TPS and re-plug them in - sometimes the connections get weak and a good unplug and replugging in cleans up the connection.

Try this 1st - it's the cheap easy stuff 1st. Let me know how it goes.

 

[01PONY]

I also think the o2 sensor is going south, but would changing that take care of the other 2 codes? Those are the codes that have me wondering.

 

[Delray Dude]

I could see the bad O2 throwing the code for the MAF or Injector Pulse - as the computer is trying to compensate for the reading from the O2 - and the pulse or MAF is out of the norm parameter because of it.

As for the EVP - taking a wild guess - maybe the thing is stuck or sticking - that too might throw off the MAF if you are getting more exhaust in the intake than the computer knows about - could throw off the MAF reading.

Has any mods been done to the engine?

I'd personally block the EGR tube to keep the exhaust from entering the intake (but leave the EVP) electronics hooked up - letting the computer think it's recirulating exhaust.
Also remove the air restriction in the air muffler if you haven't already.
I'd also find a 1993 or 1994 Ranger exhaust manifold - they are a true tube header and the literally bolt in place of the cast manifold - the pipe to the exhaust is in the same location. 1995 to 1997 Rangers are similiar but do not have the O2 sensor bung - they locate it in the exhaust pipe instead.
One is for sell on E-bay right now.