Some of you may remember my continuing problems with the CEL and codes 171 and 1131 ... to bring you up to date, here are all the things I tried in an effort to make the CEL go away permanently ...
I have:
- replaced the upstream O2 sensors
- replaced the PCV valve
- replaced the air cleaner
- replaced the fuel filter
- replaced the MAF
- replaced the IAT
- tested the EGR valve
- inspected the various intake piping that goes to the intake manifold (everything seemed OK)
- looked & listened for other intake leaks
- used injector cleaner
all to no avail.
So, for one last hurrah I decided to inspect the spark plugs. At 90,000 miles pulled all six out, and noticed a
slight difference in the amount of carbon buildup on the platinum tips -- the rear/Bank 1 plugs had clean tips, whereas the front/Bank2 plugs' tips were ever-so-slightly fouled. Since the codes suggest that Bank1 was running lean, these plugs were consistent with the codes.
The plug gaps had grown to 0.075" or so (spec is 0.054"), and the platinum tips were really really thin -- like a sharp pencil tip (not at all like a conventional, non-platinum plug). These were the original factory plugs. I don't know if these plugs came like this (really thin tips), or they had worn down -- regardless, I replaced them with some $1.99 Autolite Platinum ones that have what I would call "conventional" tips.
I also decided to check into the idea that maybe I have a connector problem -- so I used a DMM to verify the connections of the Bank1 upstream H02 sensor against the main PCM (I think that's what ford calls the computer) connector -- they were fine. Then I buttoned it all back together,hooked the battery back up (the codes were thus cleared), and went started it up.
One think I noticed instantly was that the car started much more quickly. I went for a test drive ... 25 ... 50 ... 75 miles and
NO CEL! I put another 75 miles on it yesterday in mixed driving ... NO CEL! So I went in for a CA smog check this morning -- it passed with flying colors:
2500rpm:
HC PPM 7/130
CO % 0.00/1.00
CO2 14.6
02 0.0
738 rpm:
HC PPM 3/100
CO % 0.08/1.00
CO2 14.4
02 0.0
Wow, that's pretty clean for 90,000 miles!
So, when all is said and done, it seems like my spark plugs wearing out was the cause for the CELs. It seems odd, but it did happen slowly (the CEL would come on, go off, come back on, etc. until it always stayed on), and the codes were all for Bank1, where the plugs look "less correct" than in Bank2.
All I can figure is that combustion was somewhat compromised in those cylinders due to plug wear and increased gap, and the computer was unable to compensate for that.
Too bad I spent around $300 when all I needed was $12 in plugs!
Hope this helps someone with my same problems ...
