Here are the latest Reader Questions…
Curious if you might help me troubleshoot a Oil Pressure Concern that I have. Have a Mod Hi Mileage (145K) Avalanche with the 5.3l V8, a common Chevy motor. During Start up and first few miles, Oil pressure runs about 40-55 PSI on the dash gauge…smooth idle at stop signs. When Motor reaches operating temp in around town driving, PSI drops to 20-30 PSI, and when stopping after extended road driving or uphill operation, begin to get slight rough idle and PSI in the 15-20 range…Run Mobil 1 5W30, change at 6K interval, but 2nd owner.
Brother in law thinks that I may have an Oil temp issue, partially blocked oil cooler, etc. No oil temp gauge, only trans and coolant temp. Any suggestions about diagnosing this issue? Maybe something else. Had the pressure measured digitally, range was 20-50 PSI, they stated to worry if drops to 12 PSI. Would like to get more miles out of the powerplant...
First thing to do is establish what the normal operating psi is at various engine RPM. The next step is to verify what the actual oil pressure is, using a gauge (as opposed to a sender). The third step is verify you are using the correct/specified viscosity of oil. Too thin/thick can affect pressure significantly and in newer engines can also cause problems with systems such as variable valve/cam timing, which often use oil pressure to operate.
Once you have the answers to the above, you can determine whether, in fact, your oil pressure readings are too low or too high.
That said, I doubt you have an oiling problem. It sounds more like a tuning problem. Plugs, coil pack/wires/dirty injector, etc.
Eric, have you had a chance to look into the manual transmission RPM hang when shifting the Subaru Forester? Just wondering if you had found anything related to reprogramming the computer.
There are two issues here. . . finding someone who can reflash/reprogram the ECU and warranty coverage. While there are aftermarket sources for the WRX 2.0 engine, I haven’t been able to find anything for the 2.5 engine, unfortunately. Anyone reading this who has more info, please chime in.
The other issue – warranty coverage – is the biggie. Subaru will likely void your warranty if the ECU is modified. You’ll have to decide whether that risk is worth the prospective benefit.
Many new cars – not just Subarus – have the same problem you’re dealing with. It’s the result of drive-by-wire/throttle mapping, which is increasingly set for maximum mileage rather than best driving characteristics. Same goes for automatic transmissions, by the way. Many of them will “jump” up multiple gears (especially on a downhill) in order to get into the top overdrive gear, for maximum mileage. It feels really weird sometimes – as though the car is surging forward.
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