Pinging/Knocking

[meprntr1]

Hello everyone. I have a 05 Impreza RS Wagon & from day 1 I have been having a ping/knocking noise. Happens when I acclerate or go up hills but mainly acclerating. Tried going from a 87 octane to 89 & still no change. Took to dealer & they put it on the machine & said all the parts are working the way they should. I have only 3400 miles on this so is this really normal for a subaru? I.t drives me crazy

[1 Lucky Texan]

Hello everyone. I have a 05 Impreza RS Wagon & from day 1 I have been having a ping/knocking noise. Happens when I acclerate or go up hills but mainly acclerating. Tried going from a 87 octane to 89 & still no change. Took to dealer & they put it on the machine & said all the parts are working the way they should. I have only 3400 miles on this so is this really normal for a subaru? I.t drives me crazy

 

You could try an ECU reset after switching to 89. (disconnect the neg. batt. cable, step on the brake pedal for a coupla seconds - wait 15-30 minutes, reconnect and drive normally - expect a little odd starting/performance for a coupla drive cycles - maybe.) It will force the system to try to correct the ignition timing to reduce pinging. Does your manual suggest mid-grade? On most modern soobs, it is likely a false economy to use lower grade gas than suggested in the manual, especially in summer in a hot climate. Use premium for a few tankfulls (after resetting the ECU as described) and monitor for pinging. If it is still severe, perhaps the dealership should replace the knock sensor. If they insist it is normal, ask for the keys to another car and invite the service writer along to test the idea.

 

note; all modern cars may experience very slight pinging under moderate to severe loads and it is considered normal.

[blitz]

Try a different brand of 89.

 

When I use Shell of a given octane, I get more tendency to knock than when I use BP/Amoco, I have no idea why ...different formulation I 'spose.

 

The other factor is the variability in the actual octane of "89" midgrade. A lot of retailers use the 89 as a repository for emptying the remainder of what's left in the tanker after filling the regular & premium tanks.

[1 Lucky Texan]

That engine has a 10:1 compression ratio. I'd stay with 91 or better octane if it were me.

[Storydude1]

Try a different brand of 89.

 

When I use Shell of a given octane, I get more tendency to knock than when I use BP/Amoco, I have no idea why ...different formulation I 'spose.

 

The other factor is the variability in the actual octane of "89" midgrade. A lot of retailers use the 89 as a repository for emptying the remainder of what's left in the tanker after filling the regular & premium tanks.

 

There is no "89 octane" Specific tank at ANY gas station. 89 is a mix of 87, and 91. 50/50 mixed at the pump. The only place with any more than 2 tanks is sunoco..87, 91, 94

 

Gas comes from the SAME rack..no matter WHO the final carrier is. Only difference between shell, Exxon, ad citgo, are the additives added AT the truck. The base gas is the same as you get anywhere else.

[blitz]

Here in Metro Detroit, Sunoco has always offered 5 choices at the pump, currently 86, 87, 89, 92, 94. Also, it was my understanding that Sunoco was the one that had a blend-pump to the exclusion of all others, but what do I know?

[blitz]

Storydude1, in response to your comment:

 

"There is no "89 octane" Specific tank at ANY gas station. 89 is a mix of 87, and 91. 50/50 mixed at the pump."

I offer partial dialog from someone who delivers fuel in Virginia/ North Carolina. Your return comments are appreciated:

 

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"Some stations do not have dispensers with the capability of blending the premium and regular, so at these stations the midgrade is blended as it is loaded onto the tanker truck.

 

Usually, if you see a blue colored ground tank cover that's a midgrade gasoline tank, which means that the pumps don't blend it; it's blended as it is loaded onto the truck.

 

Some stations may have different color codes but the standard seems to be white caps for regular unleaded, blue for midgrade, and red for premium. Yellow would be diesel. But as mentioned, some stations may be different. You might look in some semi-conspicuous place on the station's front window or near where the ground tanks are located to see a tank color chart."

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Then in response to your comment:

 

"Gas comes from the SAME rack..no matter WHO the final carrier is. Only difference between shell, Exxon, ad citgo, are the additives added AT the truck. The base gas is the same as you get anywhere else."

I offer partial dialog from the same fuel delivery person:

 

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"When Citgo, Chevron, Conoco, Amoco, Texaco, Shell, and the rest fill their huge terminal storage tanks the gas comes off the same pipeline at pretty much the same time. There is one exception: Amoco Ultimate Premium is refined an extra step, and it comes up the pipeline all by itself. Other company's 93 octane premium fuels (I don't know anything about Sunoco fuels as they aren't distributed in my area) are the same before the additives are injected into the gasoline when it is being loaded onto the transport tanker trucks."

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This lends some credance to my observation that the Amoco 93 (now BP) gives me different performance than the Shell V-power 93 from across the street. Once again, I appreciate your return comments.

[nipper]

Amoco premium has always been the gas I've been told to use when suspecting a fuel quality issue. BP smartly kept that fuel independint of the rest of its fuels when they merged. Bp also has its own refineries.

 

 

nipper

[1 Lucky Texan]

I was once told that, in those markets where there is a choice of terminals, Diamond Shamrock' corporate policy is to market the best tested gasoline. I think there may only be a few areas that have multiple terminals though. I have also heard that , though there is surprisingly little mixing in the pipeline, that any gas at the boundary between 2 grades will be placed in the terminal tank of the lower grade. So, on occasion, the regular or midgrades COULD be slightly higher octane. But great care is taken to test for the premium and not allow its AKI to be diluted.