The can says that while burning it trough the carb, the exhaust fumes will not harm the O2 sensors and the cat.

 

Well guys, I cleaned my MAF with Blue Shower II as promised. It seemed to do a fine job. I followed up with compressed air(carefully) and let everything dry thoroughly before driving. So far so good, no code. Not many miles logged yet, but I'll keep ya'll posted. I could be imagining it, but it seems to run better.

 

BTW, does anyone know if the engine is running at different settings when the check engine light is on? I was told it goes into a sort of "default" mode and is running at basic timing, air/fuel mixtures, etc. instead of "optimal" which is constantly adjusting these things.

 

I don't think so unless there is a serious problem. 95% of cel are smog sensor related.

 

So, the CEL being on isn't going to make it go into any kind of different "mode"? I was just wondering about that. I'm anxious to hear what Rockledge has to say about it.

 

If the MIL remains on after the bulb check:

The PCM illuminates the MIL for an emission related concern and a DTC will be present.

The instrument cluster will illuminate the MIL if the PCM does not send a control message to the instrument cluster.

The PCM is operating in the Hardware Limited Operation Strategy (HLOS).

The MIL circuit is shorted to ground.

Failure Mode Effects Management (FMEM) is an alternate system strategy in the PCM designed to maintain engine operation if one or more sensor inputs fail.

When a sensor input is perceived to be out-of-limits by the PCM, an alternative strategy is initiated. The PCM substitutes a fixed value and continues to monitor the incorrect sensor input. If the suspect sensor operates within limits, the PCM returns to the normal engine operational strategy.

All FMEM sensors display a sequence error message on the scan tool. The message may or may not be followed by Key On Engine Off or Continuous Memory DTCs when attempting Key On Engine Running Self-Test Mode.

There are two types of Continuous DTC's. The first type is an emission related malfunction indicator lamp (MIL) code which will illuminate the CHECK ENGINE or SERVICE ENGINE SOON indicator in the instrument cluster. The second is a non emission related non-MIL code which will never illuminate the cluster indicator.

For emission related MIL codes, the PCM will store the DTC in continuous memory when a fault is detected for the first time. At this point the DTC will not illuminate the MIL and is now considered a pending code. The purpose of pending codes is to assist in repair verification by reporting a pending DTC after one drive cycle. If the same fault is detected after the next ignition start-run cycle, the emission related MIL code will illuminate the MIL. The MIL will remain on even if the fault is intermittent. The MIL will be extinguished if the fault is not present through three consecutive drive cycles or a PCM reset is performed. Also, an emission related pending MIL and non emission related (non-MIL) code will be erased after approximately 40-80 vehicle warm up cycles or a PCM reset.

 

Good stuff Ken. I think that answers Zep's question.

Just a note, the one sensor that FMEM does not (and cannot) substitute a value for is the Crankshaft Position Sensor (CPS). If the CPS fails to produce a proper PIP (Profile Ignition Pickup) signal during operation, the engine will die, period. There is nothing the computer can do about it, no "backup values" that can be substituted. And if the CPS does not send the proper PIP signal during cranking, the engine won't start, either.

 

BTW, the Crankshaft Position Sensor is one of the easiest to replace. Been there. I actually needed a Camshaft Position Sensor, but that's what they gave me(Autozone), so I put it on anyway. I was half through the job when I realized it wasn't the right thing, anyway. After eight or nine years, it was bound to fail right? Who cares, it wasn't expensive or difficult.
The Camshaft Position Sensor is a whole other story. I'll get to that later.

Well, Ken really laid it to me with the acronyms. I asked for it. Very thorough answer, exactly what I was looking for, thank you. I beleeeeive you covered it there,bud.


1995 Mazda B3000 2WD
( it's a Ranger)

 

Glad to help and thanks Rockledge for bringing up the CPS.