Low oil pressure and boost reading solved

[analogdesigner]

I have been having low oil pressure and boost problems recently. When I scanned for OBDII codes I got a P0522 (low oil pressure sender voltage). I was also having problems with low boost, about 9 to 10 PSI. max. I replaced the sender (this is now the second replacement) and cleared the code. Now the oil pressure gauge reads correctly. The boost is back up where it should be, about 13.5 to 14.5 PSI (I have the early Ford Performance Pulley kit). I made a plot of the indicated oil gauge pressure with the old and new sender. Thanks all, Jay

 

[RALPHIE]

Thanks, Jay - interesting inter-relationship.

 

[paul b]

Any idea why oil sender unit affects boost reading?

 

[analogdesigner]

paul b,

The car's ECU controls the supercharger bypass valve under various conditions. It's possible that the indicated "low oil pressure sensor voltage" caused the ECU to prematurely open the bypass valve. I am still not achieving full boost at this moment although it's much higher than it was before I replaced the faulty sensor. I may temporarily disconnect the bypass valve to see if there are changes in the boost levels. Jay

Any idea why oil sender unit affects boost reading?

 

[twobjshelbys]

Since boost is a derived measurement it is possible that oil pressure is one of the factors in the equation, but it is more likely that the decrease in oil pressure caused the boost to be reduced as well as a defense mechanism.

 

[paul b]

Has there been a decrease in performance, or just a faulty gauge reading?

 

[BlackICE]

The inputs to the derived boost are engine displacement, RPM, and MAF table.

 

[nota4re]

I am still not achieving full boost at this moment although it's much higher than it was before I replaced the faulty sensor.

Note that the bypass valve is incapable of regulating boost pressure. It's an all or nothing kind of deal.

 

[analogdesigner]

All, in order;

paul b, yes there has been a decrease in performance. I am still not getting full boost from 2,500 to 6,500 RPM which used to be 14 to 14.5 PSI. I have not had time to disable the bypass valve.

BlackICE, yes, you're correct and I really wish that it was an actual measurement how I do believe in physics!

nota4re, yeah, it's "digital".

I'll let everyone know what happens soon as things are better, however not 100% yet. I will also be checking all of my electrical grounds.

Thanks all, Jay

 

[BlackICE]

If you didn't change the tune then the only factor that would change the boost reading is the MAF input. Either the MAF sensor is going bad, or you have an obstruction in the air intake, like plugged up air filters, collapsing bellow, supercharger bypass or screws leaking more air...

 

[nota4re]

The highest probability by far is that the ECU is receiving an inaccurate MAF reading.