I know I can't make head or tails out of them!

THe car stalls at stops signs, hard to start..

Codes:

57 - Octane adjust service pin in use / circuit grounded

or could be

157 -MAF sensor went below 0.4 volts during the last 80 warm-up cycles.
(there is one pulse before the 5 and 7)

These don't sound like they deal with my stall issue? My MAF sensor is brand new, just installed (as of Friday). So that could be a left over code.

UPDATE:

Did a running code test....

412, 538, 536 (in that order)
412 - Cannot control rpm during KOER high RPM check (I was going thru the revs during key on. held at 2k, up to 3k, down to 1k, let try to idle)

538 - Insufficient RPM change during KOER dynamic response test / Operator error (see above! I tried going thru the Revs)

536 - Brake On/Off circuit failure / switch not actuated during KOER test (my fault.. didnt hit brake)

 

Ran the running test again on Autopilot (no throttle from me)
172 - HEGO sensor circuit indicates system lean (right side)
138 - HEGO sensor circuit indicates system lean (left side)
538 - Insufficient RPM change during KOER dynamic response test / Operator error (oh get off my back already!)

 

How can I fix this? Id look for the carb screws..but it aint got any!

 

Did you read the sticky at the top of this forum about the IAC? The stalling problem sounds similar to the IAC valve problem so maybe it will give you something to look for.

Also, with it being lean, I would check the fuel pressure to make sure it is not too low. There is a port with a Shrader valve on the front of the fuel rail to hook up a meter.

 

Does it always stall at stoplights or just occasionally? Will the engine sometimes shudder violently then start running oK at a stop?

 

Theres a what-with-a-who-ina-whatnow??

I can 40% of the time, sit at a light at about 800rpms fine...and then suddenly shuddddder dead. Like I yanked the plug outta the wall. And yes, sometimes it will shuddder and not stall (like almost die)

If I sit at a light in Neutral I can usually prevent it from stalling (less load on engine)

Wouldnt the IAC fault show up on the error codes?

 

I checked and cleaned my IAC and it still runs like crap.

I wonder if my code 57 (Octane adjust service pin in use / circuit grounded) is associated with it running so lean?

 

Running with or without the jumper won't change things much. If you can put your foot lightly on the gas and it runs ok, then it is an IAC problem. You never said what year, but from the codes this is a first gen. Some fuel pressure regulators have a spring which is not centered. This causes wear on the valve seat on only one side. With enough wear, the valve slides to the side and sticks open. Usually at high vacuum conditions when your foot is off the gas. Rare but I know of about a half dozen cases. When the engine shudders, it will usually correct itself. Since you didn't mention this, I suspect you have a good old cap off the vacuum tree leak. Check on the drivers side near firewall.

 

Hmm...this cap, is it behind the IAC, closer to the firewall? Cause I noticed that one of the T's has a screw in it. I dont think thats a Ford Screw!

Ill go snap a shot with my digital camera....

(and its a 93 Explorer)

 

 

I ran the engine and sprayed some WD40 near the tee to see if the engine rev'd from that. Got no 'reaction'. I also clamped off on that screw'd tee - no difference either.

Also.. I let it die. The car rev'd up to about 2k down to about 700k, then shudderd to 500k, back up to 700k and died with a gasp.

 

Did it pass the KOEO test (first set of codes before the separator pulse. continuous memory codes are the second set of codes output, after the separator pulse)? If that "157" is a hard fault code (I expect it to be a three digit code because you are reporting other three digit codes. The computer should output either 2 digit or 3 digit codes, not both), then you may not have got the new MAF hooked up right, or there is still an error in the MAF circuit.
If it passed the KOEO test, then deal with the KOER codes. "False" lean O2 sensor codes (172 and 138) in the KOER test can be triggered by performing the test without "preheating" the O2 sensors by warming up the engine. Double check to see if this isn't possibly the case. If you're sure they were warmed up, or you repeat the test and they come back, then you should work to resolve these O2 sensor codes. Note that it doesn't necessarily mean that you have bad sensors. Vacuum leak, low fuel pressure, bad PCM ground, and a host of other conditions can cause lean O2 codes.
The 538, as you've noted, is almost always operator error. There appears to be some misunderstanding regarding the KOER test, so let me describe the test.
1) Run engine to bring to normal operating temperature.
2) Hook up code reading equipment (jumper wire, voltmeter (if desired) or code reader)
3) Turn on key and start engine.
4) Engine id is output (3 pulses for a 6 cylinder), after engine id, press on brake to test BOO
5) computer will raise the engine RPM and perform KOER test. This will take 30 seconds to a couple minutes. Be patient and let the computer do its thing. If you're ever intersted, this time can be used to check timing advance and a few other things.
6) When the computer is done and returns the engine to idle, you will receive a pulse/flash on your code reader. This is your cue for the dynamic response test. As soon as you receive this pulse, goose the throttle. Your window for performing the "goose" test is pretty narrow, so be ready.
7) KOER codes are output.

 

Shorty,

Yes, Ive repeated the test several times. The codes that im left with now are:
172 - HEGO sensor circuit indicates system lean (right side)
138 - HEGO sensor circuit indicates system lean (left side)

The engine was sufficiently hot, so what could be the next step to diagnose the problem? I may go and replace the IAS today even though I havent seen a code saying this was the problem.

What is my next step to fix the lean problem?

 

UPDATE:

Replaced IAS. Same god'amn problem. So that wasn't it.

 

Looks like it blew off the cap at one time. Lean codes on both sensors looks like a vacuum leak or low fuel pressure. But, you've had a whole borgas smoard of codes. I'd feel better if you had one ot two that kept repeating. Try measuring the fuel pump current by replacing the fuse with a 10A meter. Many crimp wire terminal connectors will fit in the fuse socket. Then you can bring a wire into the cab and monitor the current while you drive. Should have 4-5A if pressures are normal.