Hey all, I'm new here though I've been coming to check things out as a non-registered lurker for a couple years.

Anyway, I've got a '93 Aerostar 3.0 with A4LD and about 123,000. About 4 months ago the CEL started coming on and once it got under my skin enough to look into why I plugged in my code checker and performed the tests. I got a code 72 which indicates an insignificant change of vacumn during the WOT test. I've checked all I can and have replaced the MAF with another unit from a wrecker. Still, within about 2 or three miles of driving the CEL comes back on. So, using a micrscope I clean the MAF sensor to perfection and reinstall it. Same thing. Check voltage at the MAF and it appears to be in tolerance. So, I disconnect the battery to "I thought" clear all the memory and drive it the recommended 10 miles to "relearn" the PCM and still, within a few miles, I get the CEL.

Now, the odd thing is when I do a KOEO test I still get the code 72! But there isn't a KOEO code 72! Didn't clearing of Keep Alive Memory delete the DTC from continous memory, or do I have to clear those while reading the codes in KOEO.

This is really starting to get under my skin. The van runs OK most of the time but will stall every so often as I'm trying to parallel park or other low idle functions. And the fuel economy is almost as bad as my HO 1956 Ford F-100 Panel, which of course is a discussion for another forum, I'm sure.

Any suggestions? I have all the books and a CD-disc with Ford diagnostics, but nothing is really making sense here.

Thanks,

Roger

 

whoanelly
My 93 3.0 is doing about the same thing as yours. I replaced the IAC and it helped, there is supposed to be a way to clean these
but I dont know how. The one I took off was full of corbon almost like slag from welding.I put new one then it ran slow but there is a screw there to speed up idle some what. I think idle should be
about 700 rpm without conroller pluged in. I thought I was the only one that got codes that are not listed. When mine started this I thought it had gotten wet,that is what it acted like any way.

 

I feel like such an idjit. I've run and rerun codes and tried so many things and then while sitting (stewing) on the couch last night I had an epiphany. Perhaps this is really code 172, not 72! I then reread the book and all those short 1 pulse indicators I thought were seperator codes where actually the number 1! So, this morning on the way to work, of course the light came on (I had cleared the codes last night) and I got out, plugged in the reader and sure enough it's code 172, which does have a meaning. The book says "lean condition bank 1." So, now the question is: What does this really mean? Is this the right bank of injectors, or is there more than one o2 sensor and it's the right one that's out? My little Ford diagnostic CD (I got from E-bay) seems to indicate code 172 is diluted oil and has a bunch of tests for the PCV valve and such, which doesn't make a lot of sense. On another web site there is mention of a pressure regulator in the fuel rail that may be failing. Anyway, a lean "reading" condition could set the EEC to try and enrich the A/F mixture and that could be why I've got such crappy gas mileage. I'm thinking o2 sensor, but any other thoughts?

Thanks for any suggestions!

 

A search for code po172 indicates it should be for too rich a condition, not lean, which would make more sense as it seems the problem is either the oxygen sensor or the fuel pressure regulator. Both can cause overly rich mixtures and corresponding poor fuel mileage. There is a method to test the O2 sensor but given the age and mileage it is likely best to just replace it. You can do a gross examination of the fuel pressure regulator by pulling the vacuum line hose at the regulator and checking for evidence of raw fuel in the line. Any sign of it means the internal diaphram is bad and the regulator will need replaced.

Good luck!

 

I have a 93 3.0L also, and it has only one O2 sensor. If yours lasted 123,000 miles, you're already ahead. Mine lasted only about 80,000 miles. When mine went, it dumped so much gas into the engine that it fouled up all my spark plugs in no time at all.

Regards

 

Aero, I double checked all my books and it indicates:

HEGO sensor indicates system lean (RH).

I would then assume from other notes that the computer is then attempting to richen the mixture to compensate and still can't (I read that somewhere else). I'll check the fuel rail pressure regulator vacumn hose and see if there is any sign of fuel.

I bought this van at about 115,000 while I was driving my Ranger to California last summer. The Ranger made it half way through Oregon and no further. Bought the van and continued down the road. All that to say I have no idea if the o2 sensor has ever been changed, but not knowing means I may as well change it so I do know.

Cheers.

 

Oh, I forgot, I guess my confusion now is how does it know right hand or left hand with only one o2 sensor, if it's really the o2 sensor fault? In the manual it is listed as a "possible" fault, but code 172 brings you to this in the Ford Service Manual:

H1 CHECK FOR FUEL DILUTED ENGINE OIL

41/172r right or rear system indicates lean

Possible Causes:

--Fuel injectors.

--HO2S.

--Secondary Air Injection (AIR) system.

--PCV/Hose.

--Vacuum.

--CANP.

--MAP sensor. (I have a MAF sensor, not MAP)

--Electronic Ignition Coil Failure.

Key off.

Remove the PCV valve from the valve cover. Inspect both rocker cover hole and PCV for damage, sludge build up, blockage and movement of valve plunger. Service as necessary.

Run KOEO «Quick Test».

Address any continuous ignition DTC's before servicing KOER DTCs.

Start engine and let idle for two minutes minimum.

NOTE:
For a No Start GO directly to «H2».

Run KOER «Quick Test».

Are any of the above DTC's present in KOER Quick Test?

Yes
REINSTALL PCV valve.
GO to «H2».

No
For Continuous Memory DTC's 41/144, 91/139, 176 GO to «H2».
All Others:
CHANGE engine oil and filter.
REINSTALL PCV valve.
DRIVE vehicle 5 miles/55mph.
RERUN «Quick Test».

So, anyway, I guess I don't see how a lean burn condition gets translated into oil dilution.

Roger

 

It wasn't a real lean burn condition. The computer only thinks you are getting a lean burn so it dumps more fuel in, and I guess that's where the oil dilution comes in. Too much unburned fuel. Test your exhaust for excess HC. Also, your catalytic converter should be hotter than usual due to the excess fuel.

 

GOOD NEWS! On a hunch (gut feeling, whatever) I decided to replace the 02 sensor and do a Keep Alive Memory erase (I've done that 5 times now) and $55 and 10 miles later -- No Check Engine Light. It used to happen within a couple miles and stay on. So.... so far, so good!

Roger