My 1996 Windstar was laid up for awhile waiting for a new Trans ($$) for a year. Before it was put up I only got a code for the speed sensor which has been replaced. Now, I got it back on the road and it runs ok(most of the time) I get all kinds of things happening ie. stalling at low speeds (no warning) slight shuddering at times, intake backfire (like a carburated engine cold choke open) popping through air intake. when I read my OBD II reader I get :0131,0133,0136,0156,0171,1131,0401,1537,1538 . upon reading other threads I see I need to spend some time cleaning . Are all of these codes due to carbon etc?:banghead: P.S. I replaces O2 sensors just before tranny let go, they are new.

Wow! That's quite a list:

P0131 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)
P0133 O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)
P0136 O2 Sensor Circuit Malfunction (Bank 1 Sensor 2)
P0156 O2 Sensor Circuit Malfunction (Bank 2 Sensor 2)
P0171 System too Lean (Bank 1)
P0401 Exhaust Gas Recirculation Flow Insufficient Detected
P1131 Oxygen Sensor Engine Lean *Codes* A U
P1538 Intake Manifold Runner Control Stuck Open
P1537 Intake Manifold Runner Control Stuck Open

It's hard to come to a firm conclusion with all of this. But I'll guess is that the O2-related codes are left over from before the sensors were replaced.

The IMRC-related codes could be a factor here. The solenoids that control the intake manifold runners are noted for failing when old (search the forums for "IMRC" for more info). The EGR valve could be bad or have plugged passages - but I mistrust that code with everything else going on here.

I'd proceed by zeroing out the current codes - and then running the van for a short time (well, until the check engine light comes back on) and see what codes show up first.

The codes show in this order: 0171,1538,0131,0136,0156,0401,1131,1537,0133 after I clear the codes this is the order they reappear. Bob

Let me make sure I've got this right:

- The codes listed above all appear when the van is scanned.
- You clear the codes...
- If you scan now, *no* codes appear (prior to starting the engine)
- After starting the engine, the 'Check Engine' light comes on, and all the codes listed above reappear immediately (or at least very quickly).

If that's the case, I find the O2 codes interesting: The engine controller isn't supposed to pay attention to the O2 sensors (i.e., running in 'open loop' mode) until it senses they're warmed up (i.e., now it can run in 'closed loop' mode). I'm presuming the engine isn't (yet) warm when these tests are taking place. Is this the case?

I'm not quite sure how to proceed. You can do some checks on the functionality of the EGR and IMRC.

Anyone else have ideas?

I can't comment on this directly but you may want to get someone with a graphing scan tool to see what those O2 sensors are doing.

My question would be, did you use Ford parts or other?

I had a lot of problems with aftermarket parts in the last few years. One example....I replaced a therm sensor in a Saturn with an aftermarket. It kept overheating on me after replacement just like before. I suspected the connector wire so I cut it off to test it and it was fine. I tested the sensor with a multimeter and thought it was fine. Reassembled and had the same prob. After a year of running the A/C non-stop to switch the cooling fan on so it wouldn't overheat I finally replaced the therm sensor and pigtail with one from Saturn and it never overheated again.

If it started happening after O2 replacement I may suspect that but it could be a million other things. Someone with a good scan tool could rule that out though.

P0401 on the windstar is VERY often the DPFE, which is what senses the EGR flow.
This is super easy to replace.
Another cause of that code could be clogged EGR ports......a bit of work to get to for cleaning.......as you have to remove the upper intake manifold.

Stalling at low speeds.......often caused by the IAC.....I would try removing it and cleaning it with WD-40 or SeaFoam "Deep Creep".....sitting for a year may have caused it to become sticky.

The P1537 & P1538 might also be caused by those runners becoming sticky after sitting. Also, yes, the diaphrams in the actuators can develop a leak......only 1 needs to leak to cause both to not work.
The intake runners are in the OPEN position when the engine is NOT running.....then they close when the engine is started (vaccum is required to close them).
Again.....I would take the cheap and easy path......and see if they are physically stuck.

Oxygen sensor codes make me wonder how your battery is.
1. Check the connections for the wires to the sensors
2.If the battery voltage is a tad low........maybe strange things will happen.
3.Another possibility is an issue with the wires......and / or wiring harness someplace being damaged during the repair process.......
4.Including........very important.....a ground connection left unconnected.

Another, long shot......what is the coolant like?.......if it is old....and has become acidic........then, believe it or not.....It can cause a kind of battery type situation.......acid, different metals........generate a voltage, which can cause sensor reading issues.

I was able to buy genuine Motorcraft oxygen sensors from www.rockauto.com

Check for a vacume leak the fact the IMRC are open and your also recieving a 171 code would lead me to believe that when they were reinstalling the transmission they missed a vacume line or switched ones around. Like wiswin said 401 very likely the dpfe. I would start looking for a vacume leak first. Reset the codes and check CEL when the light first comes on it is hard to believe you would get that many codes right away like phil1 said. Maybe the codes werent completley cleared the first time.

I tried the simplest most recommended fix and it worked ! I fed in a can of Seafoam though the manifold vacuum , it smoked the neighborhood up, I then took it for a ride . when the smoking cleared up, I checked my codes and the ALL were gone ! Thank You all for your help and suggestions. I will keep you posted whether it is fixed or no. So far so good. Thanks again, Bob

don't wory about the o2 codes untill the 0171 is fixed - a lean engine will cause 02 codes - first thing is to look for vac. leaks - these vans are very problematic for vacume - if you don't find any unplug the mass airflow sensor and see if the lean condition improves - the imrc codes will also effect the fuel mix. check the runners for movement when the engine revs high even at idle they should move but are known for sticking and broken clips on the linkage. the 0401 is normaly a dpfe on fords but windstars are common for carboning the egr ports. any questions email me ( normaly check email a few times a day while I'm at the shop).