North American Turbocoupe Organization

EEC codes kicking up! and part assistance?
Tedybear315 Offline
Junior Member
Okay Kids!  (I'm old....)

Finished up the transmission work.  And ran head long into check engine light kicking on.  It was coming on at random while driving and shutting itself off after a few moments.

First run:  EEC-IV codes spit out:

Code 42:  Rich/ O2 sensor not switching.  We didn't have it running for to long, as we where filling the transmission back up. 

Removed the sensor and found a FORD/Bosch original!   Swapped our supposedly good "working spare" into it.  (Aftermarket, looks way different from the Bosch)

Drove home, car drove fine.  CEL came on after a few miles and I just pulled the codes:

Code 41:  Lean
Code 42:  Rich
Code 65:  Intermittent O2
Code 72:  PCM re-initialized  (Expected, so can be ignored.  I remove negative battery cable and shorted it to the positive cable to 'clear' everything the ECM had stored.)

Car still runs and drives okay!  I'm thinking it's probably due to have both the O2 sensor and the wiring pigtail replaced.  It gets a bit cooked in that area, so it's not hard to replace while it's apart.

Thoughts or ideas?   I do not really see a "Lean Code" (possible fuel starvation issue) combined with a "Rich Code" which points to the reverse.  The fact it's a code 65 as well?  Think our spare was bad.  Can't see dragging the fuel pressure gauges out when both the 41 and 42 are counterpointing each other for a possible fuel issue.  Plus she drives decent.

Sidenote:  We did replace the EGR valve with the spare as noted on other post.  However we do still get a running code for inop EGR.  The small solenoid is bad on this ol' girl.  The donor car has the same valve, but it's also dead.  Can't seem to find it anywhere!  The ones online visually do not look the same, and the 'key' on the connector is in the wrong spot.  Anyone ever replace that valve on an '87 or '88?


vegas_ss Offline
Senior Member
I have gotten an intermittent check engine light relating to the O2 sensor after the battery was disconnected. Usually happens when idling for an extended time such as when stopped at a light. Revving the motor will turn the light off after a few seconds. After 3 or 4 cycles of open/closed loop driving the issue resolves itself. Swapping the O2 sensor with a new motorcraft sensor didn't change anything. I think the O2 sensor cools down a little during idle and it may take some time for the system to relearn/adapt.
1987 TC, 5sp, Boport Stage 3 Head/2.1 Cam
1996 Impala SS, DCM, Borla Cat Back, too much other stuff!!! (SOLD)
2009 Pontiac G8 GXP 6M, 6.2l LS3, Kooks Long Tube, Hi Flo Cats, Mild Cam

Jeff K Offline
After the battery disconnect of more than a minute, the KAM (keep alive memory that stores the adaptive information such as long term fuel trim values, IAC adaptives, etc) resets to stock as built parameters. Especially if the car has any mods, not unusual to get a few codes until the car is driven under various driving conditions so the EEC has a chance to adjust and store new adaptive parameters. With the old EEC systems like ours, it may take 100 miles of different driving conditions for all the adaptives to stabilize. Modern PCMs learn the adaptives MUCH more quickly than our old cars do.

Drive it for a few days and see if the CEL eventually goes out.

I have a 12 V 5 A computer grade switching supply that I use to power up the electrical systems on all our cars during battery changes, etc so I dont loose the KAM adaptives o, on my Tbirds, loose my higher end Sony stereo graphic equalizer settings (which I have set differently for every source), sub cutoff frequencies, etc. My 88 TC has had the electrical system continuously powered up for 20 years, and my 86 Tbird 5.0 has had the electrical system continuously powered up for 30 years.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
11 Crown Vic Interceptor
14 Toyota Camry (wifes car)
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized

Tedybear315 Offline
Junior Member
True. Each time things get 'reset' it needs to 'relearn'.

I used my "Speed Perks" and picked up a Bosch replacement from Advance. About the same price as Rockauto, and Bosch is the original brand they used.

Okay, Test drive went fine! The only lingering issue (other then the issues with the EGR never opening....darn solenoid)

The usual intermittent idle kicking up to about 2,000. I'm very concerned about the engine sitting at 2,000 rpm while sitting at a traffic light. Seems like that would be like putting the transmission into 'micro-stall testing' each time are stopped and in gear.

TPS reset to 0.94VDC. Seemed to be smooth. It did it again when we returned home. The IAC was pulled apart and cleaned/lubed. I was concerned it was sticking. So we left it to idle at 2k and I pulled the plug on the IAC. Kicked back down to 750RPM where the base line is supposed to be.

Research time I guess. It's a common enough issue and there is a lot of research available.


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