: PCM Data, PD42 Octane?



bluegizmo83
09-01-07, 03:11 AM
I'm woundering how the PCM Data sensor PD42 reads octane? Mine seems to always show 87 octane, even when i fill up with 92

codewize
09-01-07, 09:05 AM
What? I've never heard of any sensor that reads octane. I don't think that's something you can obtain with a sensor.

What are you looking at? And what vehicle are we talking about.

.

AJxtcman
09-01-07, 09:54 AM
I'm woundering how the PCM Data sensor PD42 reads octane? Mine seems to always show 87 octane, even when i fill up with 92

This is an old turd?
OBD I?
The knock sensor and a Knock module would calculate the octane rating in 96 to 99
On 92 to 95 I would believe it would be the Knock sensor and MemCal.
If you have a bad Knock sensor I would think the common failure would to be having a 93 reading all the time
If you have too much Compression it would cause a false low octane reading.
This could be caused from carbon build up.

bluegizmo83
09-01-07, 12:37 PM
Its a 1995 Seville STS.

AJxtcman
09-01-07, 03:11 PM
I would say that the knock sensor is picking up noise. The noise is either Spark knock (from carbon) or an internal engine noise (like a lifter), but I have seen a idler pulley bearing retard timing once.

codewize
09-01-07, 09:01 PM
Sweet. Very interesting stuff here.


I would say that the knock sensor is picking up noise. The noise is either Spark knock (from carbon) or an internal engine noise (like a lifter), but I have seen a idler pulley bearing retard timing once.

bluegizmo83
09-01-07, 11:30 PM
I would say that the knock sensor is picking up noise. The noise is either Spark knock (from carbon) or an internal engine noise (like a lifter), but I have seen a idler pulley bearing retard timing once.


I would have to agree with the carbon thing... I've noticed while watching PD40 (knock sensor retard) and when the engine is cold or just warming up, there is 0 retard under WOT, after the engine warms up (operates around 210 degrees) i get between 1.5 - 3.0 retard under WOT. Thats with 92 octane at the pump (though PD42 sensors still reads 87 octane). Gonna run a bottle of injector/carbon cleaner in a tank see what happens.

bluegizmo83
09-02-07, 04:16 AM
Also, does anyone have any idea how much power I may be losing under WOT when the knock sensor is retarding my timing 1.5 to 3.0 degrees?

codewize
09-02-07, 08:47 AM
Use Lucas or Techron injector cleaner. Nothing else. Both can be found at Wal-Mart or probably any automotive store.

AJxtcman
09-02-07, 11:14 AM
Use Lucas or Techron injector cleaner. Nothing else. Both can be found at Wal-Mart or probably any automotive store.

I am not sure this will help.

Injector Cleaner and today's fuel (That is mandated to clean valves) will clean the intake from the injectors down or at least reduce deposits. All the crud from the injectors, valves, and runners now get washed into the Combustion Camber. It now gets burned in the CC. Now you have the crud in the CC and the Chemicals used to move the crud to the CC. This is a problem. The deposits in the intake are about 75%+ fuel. It is made up of the that last little bit of spray when the engine shuts off. This dries and over time builds up. If a injector have one drip every 10 times it is shut off you may never be able to tell. The Chemicals used to clean this needs to be the resistant to drying in the hot intake. Techron is a Chevron product so the rest of the fuel companies use ?? Back it the late 90s and up until recently the engine that had piston knock on cold start up was caused by carbon on the tops of the piston smacking the head. This is why pistons are now coated. The fuel companies won on this. The residue in the combustion chamber was semi gooey and semi plastic. Almost like a Jolly Rancher that was left in the sun. This is what is left in the CC from the Chemicals.