Check engine light insanity

Please help. I hate to post a new thread but I've read about 25 of these and since I don't know how to do the work myself, it's not helping much. I have a local mechanic who I like but he's not very creative at trying to find new reasons for same problems so maybe I need someone else.

Bought a 2000 Ford windstar 3.8 in 2004 from a used dealer. Did carfax, etc. and it all seemed ok so we bought it.

2 weeks later the CEL came on. Crappy dealer refused to help, nightmare began (luckily they're out of business now though!)

EVERY year I fail emissions because of the CEL. It has NEVER stayed off for more than 40-50 miles, year after year. Every year I get just about the same read outs from the little checker things. Every year I have to pay at least $400 in repairs before I can get the waiver for the next year. I've done EVERYTHING the codes say is wrong.

Last year all the 02 sensors have been replaced, also the intake manifold system, I always do regular oil changes, maintenance, etc. I'm pretty sure that's the third time for this stuff... up until this year, the dumb light is the only issues I've ever had with the van - I've been happy except for this.

I really feel like it's the actual light or sensor that is the problem, NOT what the codes are saying is the problem.

I have to reregister again this month and hate to waste my $400 when maybe possible I could get it (the CEL) fixed and NOT fail year after year.

Also now the air conditioning has stopped working and the car is starting to idle weird at stop lights - could that be related or are those different problems entirely?

I'm so fed up but don't know where to go or what to do and even with all this figure fixes are cheaper than a car payment...

Just hit 100K this year and had a 90K checkup done (yes I'm a little late). I think I'm at about 103K now.

HELP??

Can anyone tell me what DPFE, TSB, EGR and PCM mean, respectively.

I think I have the same problems as everyone else here but don't know what the acronyms stand for...

You need to help yourself by getting the actual alpha-numeric code(s). AutoZone (and others) will read for free. This is what I tell my S's & D's: ... "get the code(s), (if they exist), before you tell me of car issues".

Diffirential Pressure Feedback Egr (sensor) ..... proves the exhaust feedback is "correct".

Technical Service Bulletin .... a publication by the manufacturer that stresses some particular technical information.

Exhaust Gas Recirculation .... system/valve/sensor/regulator/tubes/etc, etc.

Powertrain Control Module ... controls engine and transmission functions.

Thanks for your responses. I'll get the codes and post them. I know it's usually something running too lean or oxygen sensor or banks but I'll get it right.

Most any auto part store person will be more than happy to tell or show you the code or codes that they come up with when the read them.
They usually don't unless you ask....because most people just want to be told what part to replace.......however, regardless of what kind or brand of car (as long as it is 1996 or newer), you are best off getting the actual code.....as a internet search will help you get to the actual solution to the problem.
Be prepared to write them down.

Here is a website you need to visit.....add it to your favorites so that you can refer back to it.....as it applies directly to the 2000 windstar and is excellent information (and pictures).
You (or your mechanic) should verify that this has been done to your 2000 windstar.
You can print it out and take it to your shop.

http://leckemby.net/windstar/windstar01.html

If it is P0171 and/or P0174 It is very unlikely that there is anything wrong with your oxygen sensor(s).
Having already replaced them, it is nice to hear that now.....but don't replace them AGAIN for this code(s).
Often they will advise you to replace the oxygen sensor when this code or codes come up...........but they are wrong (at least for the windstar).
In other words......the oxygen sensor is telling the computer something that it (and you) don't want to hear, but don't shoot the messenger.
There ARE specific codes that will tell you if the oxygen sensor is truely bad.
But the codes that I listed above......the sensor is reporting a real condition.

It is almost always a "vaccum leak", air getting into the intake......from any point that is past the MAF, Mass Airflow Sensor.
The MAF is mounted on the Air filter "box".....more like a tube on the windstar.......
It is located between the air filter element......and the throttle body.

If air leaks into the intake path (which is at a vaccum because it is being drawn into the motor) from a location that is AFTER the MAF....then the PCM (computer) does not "know" about it.
If it does not know about it.....it has a hard time making the proper adjustments to the fuel flow......causing there to be too much air going into the cylinders......for the amount of fuel that is being sprayed in by the fuel injectors......causing the air fuel ratio to be lean (too much air).
This is what the oxygen sensor are reporting......a condition that truely is present.

The "ideal" air / fuel ratio is about 14 / 1 .... 14 part air to 1 part gasoline.
There is NO sensor the measures fuel flow or pressure......the computer "Knows" the flow rate of the fuel injectors when they are open, so if it opens them for a given time (and it is a VERY short time), then it knows how much fuel has been added to the intake.

The MAF (Mass Air Flow ) sensor senses how much air flows into the intake.
Knowing this.....the computer "knows" how much fuel is needed, and calculates how long to open each injector for each cylinder.
The oxygen sensor in each exhaust pipe (1 for the front 3 cylinders and a 2nd one for the rear 3 cylinders) tells the computer how well it is doing......and the computer can "fine tune" the mixture to maintain the ideal air fuel mixture over a range of driving conditions.

Now, you have 4 oxygen sensors.....and 2 catalytic conveters.

When they talk about bank 1 and 2.....that is the front and rear banks of cylinders....Each having its own catalytic converter....

When they talk about "upstream" or "sensor 1", that is the sensor that is BEFORE the catalytic converter......located between the motor and the catalytic converter.
These sensors monitor the exhaust to determine the air / fuel mixture , to determine if it is "just right" , "too lean" or "too rich".....so that the PCM can make the proper adjustments.

When they talk about "downstream" or "sensor 2", that is the sensor that is AFTER the catalytic converter......between the converter and the muffler....or tail pipe.
These sensors ONLY monitor the catalytic converter to make sure that it is working.


P0401, insufficient EGR flow, usually either the DPFE or clogged EGR ports in the lower inake manifold.
This is ALSO cover very well in the link that I posted above.

EGR is Exhaust Gas Recirculation, part of the emission control system.
Some of the exhaust from the motor is fed back into the intake manifold.....and into the cylinders.....they have found that this can reduce Nitrous Oxide emissions from the vehicle....also reduces cylinder temperatures.

DPFE is Delta Pressure FEedback (or Differenctial Pressure) If you look at the DPFE, you will see that there are 2 small hoses that go from it to a pipe.....which goes from the front exhaust manifold to the intake manifold (through the EGR valve).
This pipe is the EGR pipe.
Inside that pipe....located between those 2 hose connections is a small "restriction" or narrow place in the pipe.
The exhaust manifold, and pipes are under pressure from the exhaust exiting from the motor...
With the EGR valve CLOSED.....no air moving through the pipe that the hoses go to......the pressure is the same on both sides of the restriction.
When air (exhaust) flows through that pipe......the restriction slows the flow down.....so the pressure on the exhause manifold side is higher than on the motor side.....
More flow through the pipe......more difference in pressure between the 2 hoses that go to the DPFE box.
The DPFE senses the pressure difference.....and sends a voltage to the Computer (PCM) that tells the PCM how much air is flowing through the EGR pipe.

The PCM determines how much exhaust gas needs to be added into the intake (recirculated) for best combustion for less polution.
It sends a command to open the EGR valve.......and the DPFE tells the PCM how much flow there is through the EGR system.....and the PCM constantly adjusts the EGR valve to maintain the desired flow.
However, the DPFE is a somewhat common failure.......
If it stops sensing flow......then the PCM keeps the EGR valve open too much, which can cause rough running.......and it STILL thinks that there is not enough flow.....when there is too much flow, because the sensor (DPFE) is defective.

The DPFE is easy to replace.
The EGR valve rarely fails on the windstar.

As far as the A/C is concerned......if it is not running at all......or you can feel it cycle on and then off...but get no cold air.....
I would have it checked out at your shop.....they can check to see if it has lost the refrigerent (leak) or if something else is amiss.
The idle speed should bump up some as the compressor engages.......to handle the load.
If the load is much less than expected (no refrigerent charge) then....the RPMs might bump up more before coming back down as the PCM is expecting a certain load as it turns the compressor on, not finding the load that is expected.................

I didn't see a common Windstar repair mentioned that some repair technicians have missed. This is the need to clean EGR ports (the points where the exhaust gas actually combines with fresh air) located in the intake manifold. If these have never been clean on your vehicle, it may be the cause of your problems.

My '96 Windstar rarely gives an EGR code even when thise are the root cause of misfire problems (which are reported). The repair requires almost no parts, only some time to access the ports under the upper intake manifold.

Had Autozone check last night and it was showing codes 161, 171 and 174. Pretty sure from what he rattled off (lean banks, oxygen something, emissions something) that it's the same dumb codes I get every year.

So what would you have me do next?

Ok I didn't realize anyone had replied to me since the first reply so now reading through all those I think I can have my husband do the 171 and 174 codes with the help from that manual. THANK YOU!!!!

I saw this on the sticky note about 161 - but what would we do to fix that? P0161 Downstream Oxygen sensor bank 2 HEATER circuit malfuntion
Downstream sensors monitor the catalyic converter operation

I checked through some of my service records since we do this every year and besides the intake manifold system and the oxygen sensors we've also had the fuel filter and fuel injection system redone, and the mass air flow sensor. That's all I could find records for in the last 3 years so each of those is at least 3 years new or has been done more than once in trying to fix the CEL.

As for the air conditioner I had them look at it and they said it's the actual plastic fan that broke - a really cheap part but that I'll have to remove the entire dash board to get to it and that the back vents are blowing it (and heater too) but just not the ones in the front - - is that something you'd advise I take into the shop or my fixer upper h can try? He can do stuff like spark plugs and brake pads but entire dashboard makes me queasy... Thanks for all your input!!!

I would first deal with P0171 and P0174. If you correct the air leak issues along with possible plugged EGR jets .... the other codes just might go away on their own.

I agree with 12Ounce. But as far as the ac goes, you don't usually need to take the entire dash apart to replace a blower fan, almost all that I've seen are usually quite easy to replace as they hang behind or below the glove compartment.

Just for shiggles, have you ever cleaned the MAF?

I have no idea. If it isn't a regular part of the things that have already been done then no. So far h has never worked on my van other than brakes and oil and spark plugs... I always take it to a shop - but we do have a receipt for services that just says "mass air flow sensor" and it was about $500 so I don't know what exactly that meant... that was 2 years ago.

I was talking about recently. But that's ok it just means they replaced the mass air flow meter instead of cleaning it last time. Weather it was bad or not, one will never know. BTW that was a bit on the expensive side for a MAF. I'd still try some MAF cleaner instead of replacing it this time as it needs to be cleaned from time to time to help keep it accurate (brake or carb cleaner will not do).
The lean condition that some of the codes point to could also be a large vacuum leak (air entering the system that's not been accounted for by the system)...like the egr being stuck open, broken vacuum line or a bad gasket.

Have you been taking it to the same shop every year? Because if "h" isn't comfortable doing the work, I'd try a different one as many shops just see dollar signs instead of people needing help. The thing is, it's actually pretty easy and most people just think it's harder than it really is (most times lol), the hard part is the diagnosis.

Maybe I'll price shop this year. It's always been the same mechanic up until last year when he had at least 1 1/2 week wait so I just took it to Tunex... they did the fuel injector/fuel pump stuff because I'd had the oxygen sensors done pre-inspection (in anticipation of the fail, still didn't help and it was a waste since they'd been changed the year before...)

We keep pouring money into it but at least I'm learning a lot from this site - wish I'd found it 5 years ago when we were failing for the first time.

You might keep you eye open to see if any of your neighbors have a similar Windstar ... say 1999 - 2002. If so, they may have already discovered a good mechanic who's familiar with this particular models weaknesses. The 171 and 174 codes can be fixed in a couple of hours ... by someone who has had the experience already.

But if the guy's "learning" on your dime .... look out!