2.2L 99 OBS acceleration lag- common?

[poolskaterpt]

Have my 99 OBS with EJ22, 120K on engine, 173k on chassis, Weapon R Dragon Short ram Intake (no CEL over rides needed) new timing belt, plugs & Wires. I've owned it since 140K and done some restorative maintenance on the powertrain (tranny bearing, center diff, CVs, U-joints, back to stock exhaust setup)

 

When moderately accelerating in any gear from low RPM to high RPM ( 1200- 3200) it hesitates/hiccups until 3200/3400 when it cleans up and picks up steam solidly. Damn near like hitting a powerband on your 2stroke dirtbike! like when a boggy turbo finally overcomes lag and boost kicks in (mind you this thing is not turboed!). ALso it is critical to note I am not changing the throttle position during acceleration, just depressing the pedal to mid throttle and waiting for it to tach up so it will stop hiccuping and get my butt down the road. 

 

No DTCs according to the Innova, timing is on according to spec. 

 

If I drive miss daisy it will accelerate smoothly up through the tach range. 

 

Hypotheses so far:

1) clogged fuel filter

2) fuel pump working on taking a crap

3) clogged injectors

4) gremlins, drunken gremlins

 

 

[lmdew]

Have you tried going back to the stock Intake?

Did this just start or has it always been this way?

[forester2002s]

Have you tried using higher-octane fuel, to rule out the knock sensor?

[1 Lucky Texan]

TPS ?

[Fairtax4me]

Probably knock sensor. Very common. New ones are cheap on eBay.

 

Never hurts to runs bottle or Lucas fuel system cleaner.

And Seafoam in the intake is fun for giggles even if it doesn't help.

[poolskaterpt]

Ran 91 octane through with bottle of techron and cleared it up. This started recently completely independent of intake installation so the intake is non-factor.

 

Knock sensor huh? Why would a knock sensor prevent acceleration? I'm not showing that I'm running lean. Thought that was only a component on the turbo cars.

 

Any way to test the knock sensor instead of just throwing parts at the car?

[1 Lucky Texan]

if the car has pulled timing due to 'real' knock or false readings from a bad KS, you will experience reduced performance.

 

some folks have spotted cracks in the sensor. The FSM may have a test for it. They are cheap parts. maybe cheaper than 2-3 bottles of Techron if bought from ebay.

Edited March 12, 2014 by 1 Lucky Texan

[forester2002s]

It could be that with 'regular' fuel, your engine is knocking on acceleration.

Or should I say 'trying to knock', because the Knock-Sensor will attempt to prevent knocking by adjusting the timing automatically.

So with changed timing, you get reduced performance/acceleration.

 

Using higher-octane fuel, the tendency to knock is reduced, and you get normal acceleration.

 

Why is your engine knocking? I don't know. Back in the old-days of leaded-fuel, combustion chambers were prone to a build-up of deposits. When these got bad enough, the hot-deposits could cause pre-ignition with the familiar knocking sound. But that is all in the past, now that we have unleaded-fuel and computer-controlled timing.

 

Anybody have any other ideas?

[Fairtax4me]

Ran 91 octane through with bottle of techron and cleared it up. This started recently completely independent of intake installation so the intake is non-factor.

 

Knock sensor huh? Why would a knock sensor prevent acceleration? I'm not showing that I'm running lean. Thought that was only a component on the turbo cars.

 

Any way to test the knock sensor instead of just throwing parts at the car?

Doesn't matter of its turbo or not. The knock sensor does the same thing. It pulls timing if it detects knocks.

Lots more goes into detonation than just running lean. Fuel octane is a big factor and so is compression ratio. If your engine burns any oil that can also cause detonation.

Excessive carbon buildup in the combustion chambers or on the pistons will cause detonation.

 

Big problem wih the knock sensors on these is the housing cracks and the sensor element gets corroded. Then it sends false signals. ECU pulls timing because it thinks its knocking.

[poolskaterpt]

It doesn't burn oil, doesn't have the old persistent detonation with the key off cylinder deposits. 

 

If the higher octane fuel cleared it up, the knock sensor would have to be functioning properly and the octane increase wouldn't have improved it; or am i committing improper subaru medicine here? 

 

I'll check the sensor, thanks for the help everyone. Now onto changing the front differential oil seal that is leaking and the CVs while I'm at it

[1 Lucky Texan]

suppose the sensor has failed in such a way it prevents the ECU from pulling the timing. that is, there's knocking that is unreported. Then higher octane should remedy some of the knocking.

[Fairtax4me]

It could be that the gas in your area has gone to spoob recently.

If the regular gas is causing detonation it could be because the octane content of the gas is less than its supposed to be. In which case higher octane fuel would fix the problem, and the knock sensor would be working properly.

 

It could also be that the knock sensor is malfunctioning in an "ultra-sensitive" manner, which is a pretty common failure mode. It's taking small knocks, and telling the ECU they're big knocks, so its pulling the timing more than it needs to. Higher octane fuel eliminates the knocks, thus, no more pulled timing.