Bad Mileage?

[Aredubjay]

I've noticed some prety scary mileage figures posted here lately. If you're not the original owner of your car, and don't know if your car has ever been filled up with "regular" fuel, this might be a solution. And though it says "disconnecting the battery or ECU might not clear the memory completely" I'd try it first. If it doesn't, then, you've lost nothing. If it does, then you've gained performance. Worse case scenario is to pay at your Suby dealership to have the ECU reset with the select monitor. Taken from TSB #01-137-93:


The SVX requires the use of unleaded premium fuel with a rating of 91 AKI (Anti-Knock-Index) or higher.

Unleaded regular fuel with a rating of at least 87 AKI may be used temporarily when premium fuel is not available. However, when a regular fuel is used, the ECU will learn to run on regular fuel even when a small amount is used. This may cause engine knocking, poor driveability and poor fuel economy compared with premium fuel.

Even after refilling the vehicle with premium fuel, the ECU may NOT relearn quickly on how to run on premium fuel. This process will depend on the driving pattern of the user and the length of time the vehicle is driven. The best way to ensure the ECU will fully learn to run on premium fuel is to clear the memory using the Select Monitor. This will set the ECU back to the beginning of the learning mode.

NOTE: DISCONNECTING THE BATTERY OR THE ECU MAY NOT CLEAR THE LEARNING MEMORY COMPLETELY.

If you have a vehicle with a driveability complaint make sure you confirm with the owner the type of fuel that is in the tank before you attempt any repairs.

[vkykam]

I'm pretty sure that disconnecting the battery resets the ECU, despite what the TSB says.

For one, all codes stored in the ECU are reset when the battery is disconnected.

For another, I recently ran out of gas <BLUSH!>, and when the auto club came to rescue me, all they had was regular gas. So when offered the choice of regular unleaded or no gas, I took the former option. Got to the nearest station, topped up with premium, and the next day the car was running like CRAP, the ECU was retarding the engine on standing starts, like the revs would increment a couple of hundred revs, pause, go up another couple of hundred revs, pause, and so forth until it hit about 2000 RPM. Once above that, the power was fine.

I disconnected the battery for 5 minutes, hooked it back up, and the engine has been running smooooothly since.

VK

[Aredubjay]

Originally posted by vkykam
I'm pretty sure that disconnecting the battery resets the ECU, despite what the TSB says.

For one, all codes stored in the ECU are reset when the battery is disconnected.

For another, I recently ran out of gas <BLUSH!>, and when the auto club came to rescue me, all they had was regular gas. So when offered the choice of regular unleaded or no gas, I took the former option. Got to the nearest station, topped up with premium, and the next day the car was running like CRAP, the ECU was retarding the engine on standing starts, like the revs would increment a couple of hundred revs, pause, go up another couple of hundred revs, pause, and so forth until it hit about 2000 RPM. Once above that, the power was fine.

I disconnected the battery for 5 minutes, hooked it back up, and the engine has been running smooooothly since.

VK

Yeah, I'm sure the "disclaimer" was merely a CYA measure. Gotta do it these days.