More cold weather, more idle trouble
 

Hi guys, It got real cold wherei live a few days ago. And of course my check engine light came on. I read the codes and it gave p0171 and p0174(mixture too lean). I reset the codes. Later on i was driving to work and got to a stop light. My engine of course was at a low rpm. All of a sudden it started to idle eradically and then stalled. It restarted fine and i drove to work. When i got home i did some research and found out that it could be a bad maf. It seemed like a likely possability so i got a new one. It has helped a little bit. It hasn't stalled again but it has been warmer outside.

Now, i'm thinking about replacing the oxygen sensors. When the cel comes on it always gives the code p0171 and sometimes p0174. If i understand right, the oxygen sensors are heated and need to be at 600degrees to work. There is 1 sensor on each exaust manifold, this could make sense. It only stalls and idles weird when it is cold outside. And the cel comes on after i have been driving for a little while(the sensors need time to warm up).

I have already replaced the iac a while back and it helped a lot. It had lots of carbon deposits on it. When i replaced the maf it had what looked like corrosion on the 2 wires real bad. Probably from oil on the the K+N air filter. Having to worry about it stalling every time it gets cold is a real pita. Well, anyways Other than the o2 sensors i am running out of options. Sorry about the long post.

Thanks very very much,
CAW

omg, my truck did the same thing this weekend. It stalled when i started it, then ran/idel rough. Then my C.E.L light came on too. I brought it to autojoke (autozone) but the blonde couldn't remember the Code, she told me its running to lean and give it a tune up. My trucks going to the dealer tomorow, i'll let u know what they fix, maybe it'll help you.

I dont know if this will help at all, but my 99 blazer sounded kind of like the same. When they tested it they found a vacum leak. I would take it somewhere with credentials to test it(where blondes dont work lol) JOKE dont freak out readers! Anyway my CEL went on and off periodically and seemed to stall during takeoffs, and almost felt like it had a miss on the highway. My fuel pump also went bad and showed similar symptoms- eventually wouldnt start and left me and the wife to fend for ourselves on the alaskan highway. Its a stretch, but if it is, you need a top schooled scholar to go over all of the fuel components. Half of my Blazer went bad after the the FIRST fuel pump dropped.

It probably doesn't have anything to do with the heaters. The heater circuit is monitored by the PCM and it will code for a problem. Besides, the heaters are only there to make the sensors warmup faster on a cold start and keep them warm during extended idling. They are sitting in an exhaust stream that is typically at 800~1400F shortly after starting.

It could be a failure of the sensing portion of the O2's or it could be an actual lean condition caused by a vacuum leak, plugged fuel filter or dirty injectors. A vacuum leak in the PCV hose or loose manifold bolts are common problem areas on Rangers.

my engine runs like that too when its extremely cold. cel doesnt come on but it stalls and the passenger door latch doesnt latch all the way. almost lost the girlfriend on the way to dinner for valentines day. it was a risk i was willing to take. j/k.

BTW: post #300. stone im catching up. :lmao:

The weather has warmed back up again. It has been getting warm then cold for a while now. It's going to be a while before i get this fixed. I might replace an oxygen sensor just to see if it does anything. I think they have 100k+ miles on them. The time it stalled on me at the stop light, i had been at idle for a while. I believe this is when the EGR system is susposed to kick on. I'm going to look at the EGR system for a leak. I'm also thinking about doing the air temperature resistor mod. I could do this to keep up the RPMs in the winter and take it out in warm weather. I'm still thinking over what it could be.

After doing some more research I'm thinking that it is a vacume leak of some type. I replaced a vacume hose on the evaporative emissions system, but i doubt it will help. If it is a leak in an intake gasket where would it most likely be? I have the plastic upper intake. Is there even a gasket between it and the lower metal intake? And where do i need to check for loose bolts at, On the upper or lower intake or both? I could probably take off the upper one without any trouble but the lower one may be a bit to tricky for me.

I have replaced the lower manifold to head gaskets on a 4.0 SOHC Explorer and it wasn't too difficult. A Ranger OHV intake is different and probably a bit easier to work on than the Ex. And yes, they do leak when they get old.

Well, I tried some fuel injector cleaner just to see if it would help. I'm almost through with that tank of gas and havn't seen any dramatic improvment. But it hasn't been cold since i added the injector cleaner. I've done some more research and found that some people have had trouble with a gasket in between the furl rail and intake. I've heard that this is especally a problem with 97s(my year). do you think this might be a problem too? I will probably end up replacing the intake gaskets and will probably replace any thing that could be trouble in the future while i'm at it.