The Dreaded p0174 Strikes Again!!

[pentode]

If it's a reputable shop I would think they'd be working with you if they misdiagnosed the problem.

 

[Brain75]

I'm going to go back to the post I did again....
engine-codes.com

• Dirty or Restricted Air Filter
• Dirty or Faulty Mass Air Flow (MAF) Sensor
• Intake Air Leaks
• Exhaust Gas Leaks
• Fuel Contamination
• Faulty or Clogged Fuel Injectors
• Faulty Front Heated Oxygen Sensor
• Ignition Misfiring
• Low Fuel Pressure
• Positive Crankcase Ventilation (PCV) Hose Leaks

and for those that didn't open the page and read the technician notes (from years of trying to fix this problem):
Tech Notes

The P0174 code means that more air than gasoline is detected in the exhaust gases exiting the combustion chamber. If the P0174 is set in along with the P0171 code, it is highly likely that the problem is caused by an intake leak. If there are no intake leaks, the next step is to replace the air filter and clean the Mass Air Flow (MAF) Sensor. If the problem persists the MAF or Front Heated Oxygen (O2) Sensor will need to be replaced.
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No where does it say cat, and from the way the system works, I would say blaming the cat is misguided.

I'd move all the old fuel to a spare vehicle, clean out the airbox entirely, put a new air filter in, clean the MAF with only MAF cleaner, put a fresh tank of good fuel (not the cheapest you can get at the local sav-o-mat, but a big brand, shell, bp, safeway, etc - octane doesn't matter just good gas if you can find E00, use it!), add a bottle of fuel injector cleaner - again not the cheap $2 walmart spectre but anything better, disconnect the battery long enough to blow away all the short and long term trim data, and drive it around 100 miles so it establishes accurate new fuel trim data, then see where you stand. Chances are with all that done, you will find either the code disappears or it is some wearing part you have skipped or put a cheap part on - a front o2 sensor, etc. (o2 sensors are wearing parts they have a lifespan)


My GM has gotten into this crunch right before emissions repeatedly (forget which exact code but it is always "bank 2 lean"), I learned to "make it pass" 2 months before it is due by doing a bottle of fuel injector cleaner and good gas. Reset the computer and drive it around long enough all the sensors except 1 are "ready" (the last sensor needs a laboratory to go ready, can not be done in the real world) - that takes about a full month of driving as little as I do. Then 1 month before I find one of those "drive by" tailpipe sensors and drive by that thing all the damn time so I get the required "2 passing more than 24 hours apart" and can skip taking it to a station where they microscope the bloody thing. The fuel economy on that vehicle has gotten real poor and only recently did I learn (from the GM guys forum) that fact is almost always dirty or bad MAF for my particular engine/system.

 

[deRangerous]

Oh, the shop is willing to work with him--$800+ for intake gaskets and "if that doesn't work we're stumped". I'm going to do it for him for half that.

 

[pentode]

As Brain75 said, I would advocate for some proper troubleshooting before throwing parts at the problem. My 2 cents.

 

[deRangerous]

Ok, first up;dirty or restricted air filter☆replaced

Bad MAF☆swapped for known good

Intake leak☆smoked & IAC test

Exhaust leak☆new cat and pipe

Faulty O2☆replaced

PCV☆replaced

So that leaves fuel pressure/injectors/bad fuel or ignition misfire
Truck runs really nice for a misfire but I guess I should check fuel system just to cover all the bases...Hell, I might as well send the squirters for cleaning & flow matching while I'm doing the intake gaskets. What's a little more cash on a 26 yr old, 300k+ mile Ranger, right?

 

[Brain75]

One of the reasons I said put good gas in it, my 89 (Ford car) failed about 50% of the time on cheap gas, had to just burn through the tank and put good gas in it (This was back when Colorado had every other shop licensed to do emissions testing and they did quick limited tail pipe sniffing and nothing else). You could slip the tech a $20 to make it pass and a lot of shops did it... I think half the time the tech was just failing me to try to extort the "tip" from me. One of the last passes, the muffler had so many holes in it there was zero flow and they just passed me cause all they were measuring was what did exit the pipe (nothing).

My 95 (again Ford car) passed almost all the time without issues, the one fail I remember is from fixing a leak (disconnect battery first before doing work) and then the sensors weren't "ready". (This was the period where Colo switched to only 5 testing stations in the whole state, and all they did was check the computer was ready and a really low threshold quickie tailpipe sniff - you were responsible for making sure it was fully up to temp before you arrived or you automatically got a fail if not - Closed loop mode is rich so it couldn't pass.) But by this time I switched to just always buying good gas, never cheapie gas again.. Imagine the 2 million folks in Denver all trying to go to the one government station - it was a nightmare.

My 06 (GM car) has been a nightmare to get to pass, 2 months before I have to start this ritual with fuel injector cleaner etc etc. Colo now has a station in every county and emissions vary by county... Denver metro has added the drive by tailpipe/license plate readers to a bunch of on ramps to I25 & I70, but going to Texas with it (for 7 years - Austin) it was the old first game, every "oil stop", "jiffy lube" etc is licensed and some places are a-holes some are nice... but again high quality gas and a bottle of fuel injector cleaner got me past all but Firestone.

up to you and the owner if you want to spend $50 on gas and $5-$7 on a good bottle fuel injector cleaner or $1k in labor pulling it all out and sending it off for a job that can be done at home (google "bench test and cleaning fuel injectors").


I'll give you another reason to put in good gas:
I just finished the first two tanks of full fuel on my 1990 Ranger (stock 2.9).
First tank was E10 (10% ethanol) - I clocked 299 miles and was on fumes when I hit the pump.
Second tank was E0 (zero ethanol) - luckily I can get it for the same price as E10 here locally- I clocked 349 and had more miles to go, somewhere above 1/8th of a tank.

I ran this experiment because in 2006 I worked for a company that had me drive a brand new 2006 Dodge Dakota with a service topper, and it got a full 33% worse fuel economy on E10. From 2007-2015 I lived in Denver (different job no dodge) and all I had access to was E10 - my cars got worse and worse mileage every year. If I drove up to the mountains where there are lakes at the boat dock you can get "recreational/marine gas" - it is E0. From 2015-2022 I was in Austin and again no access to anything but E10 - crappy mileage.... but if I drove all the way to the marina, and bled through the nose for it I could get E0 there. I am currently in teeny tiny nowhere Colo and have regular access to E0 (just 1 pump in the entire county but it is less than a mile from my house) and I get better behaviour and proven better mileage with both my 06 (gm) and my ranger. If the E0 is between 0 and I'd say 20%-ish more expensive it is worth it, cause you will get ~20-35% better mileage... Do your own math and run your own tests to figure out where the breakeven is for you.

 

[pentode]

Because I don't feel like rolling around on the ground tonight working on my own car problems, I'm going to jump back in here from another angle. This Ranger is in NV? I take it that NV is a state that passes/fails emissions on MIL status/engine codes?
I ask because I can't imagine a situation where an engine that is actually running lean would produce excess emissions. The only place I've lived with emissions testing is in Europe, and they actually measure the emissions there, check engine light is irrelevant.
I'm just curious what they actually test there.

 

[Brain75]

took a hot minute of googling, but the waivers section of nevada DMV says CEL/MIL must be off for 1996 and newer models - so yeah, any county that has emissions can't have a CEL.
also looks like the way Colo used to - after you spend a certain amount of money you can ask for a 1 year waiver which basically gives you a year of exempt status to get it fixed (or sell it).

Nevada Emission Control Program

dmv.nv.gov

and since post #1 says 1999 model year....

 

[pentode]

do they actually bother to plug a computer in or do they just check for the light?

 

[Brain75]

if it is like CO & TX, both - If the light is on, then check the box "fail" and move on to the next car - don't investigate at all. If the light is off, then plug in their computer and look for "all but one" of the sensors to read "ready", no CEL codes (people removed the bulb as an early way to try to pass), etc etc - microscope... Which is why I strongly recommend the drive by tailpipe sniffers on the on ramps, all they check is the actual pipe puke, and you can BS those by gunning it up to the area before and letting it coast through the zone it checks - no power on the throttle means very little coming out the exhaust.

The drawback to the drive by, you have to get 2 passing more than 24 hours apart (to prevent people from driving past 10 times in one day just to get a pass), and they give false fails in rain, fog, smog, cold damp weather etc etc - so you really have to drive past em every day in a commute over and over and over to hope you get 2 good in 30 days of tries.

 

[pentode]

OK, given that most ECUs are going to deal with that by throwing more fuel at the problem, I guess asking for a proper emissions test probably won't help.
So, referring back to the earlier post, I will nitpick as that's my second best quality after being a cheapskate.

Bad MAF☆swapped for known good

Known good meaning from a properly working engine?

Intake leak☆smoked & IAC test

This is from the "reputable garage" that was offering to throw parts at the problem for $800? Did you watch them smoke test the intake?

Exhaust leak☆new cat and pipe

Which new pipe? In front of or behind the cat? And even more importantly, where did this cat come from? OEM? We all know parts are bad these days and cats have to be right at the top of the list.

Faulty O2☆replaced

OEM? I seem to recall the member said he'd replace it with one off his truck but is that what actually happened?

Sorry to sound so negative, but according to my wife that's what I do.

 

[Brain75]

post #15 you say you are already over $550 at a reputable shop, if that shop was on the list of authorized emissions places in NV then it exceeds the $450 threshold and you could just apply for a waive right now... if it wasn't a sanctioned shop well then the dollars spent don't count for nothing.

 

[pentode]

if it wasn't a sanctioned shop well then the dollars spent don't count for nothing.

Nor does the diagnosis.

 

[deRangerous]

I haven't turned any wrenches lately and it's only going to be 104° most of the weekend
so...Anybody remember where that "intake manifold bible" can be found?