HHR SS low power / boost until gas pedal is flicked
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Joined: 10-13-2011
Posts: 39,900
From: Welland,Ont Canada
When the HPFP takes over from the in tank pump. In first post it’s mentioned the fuel pressure is only 1,100 psi, however the pedal flick draws attention to the throttle position sensor.
Last edited by Oldblue; Aug 8, 2024 at 08:13 AM.
Senior Member
Joined: 12-05-2014
Posts: 3,330
From: Northern Ohio
I don’t think this has anything to do with fuel pressure or pumps. This sounds like the timing is being rolled back due to a detected, knock. “Flicking” the throttle, i.e. releasing and stepping back down, would momentarily at least cause the knock to cease. I don’t know if the ECM would immediately go to full timing advance in such a case.
The car is old enough to have some carbon accumulation. Does it seem to happen more often when the engine is good and hot and less when the engine hasn’t heated up much yet?
What fuel are you using? What spark plugs? Tuned?
No CEL. Have you scanned for codes? Any other recent issues?
The car is old enough to have some carbon accumulation. Does it seem to happen more often when the engine is good and hot and less when the engine hasn’t heated up much yet?
What fuel are you using? What spark plugs? Tuned?
No CEL. Have you scanned for codes? Any other recent issues?
Thread Starter
Senior Member
Joined: 09-24-2011
Posts: 118
From: Long Island, NY
I don’t think this has anything to do with fuel pressure or pumps. This sounds like the timing is being rolled back due to a detected, knock. “Flicking” the throttle, i.e. releasing and stepping back down, would momentarily at least cause the knock to cease. I don’t know if the ECM would immediately go to full timing advance in such a case.
The car is old enough to have some carbon accumulation. Does it seem to happen more often when the engine is good and hot and less when the engine hasn’t heated up much yet?
What fuel are you using? What spark plugs? Tuned?
No CEL. Have you scanned for codes? Any other recent issues?
The car is old enough to have some carbon accumulation. Does it seem to happen more often when the engine is good and hot and less when the engine hasn’t heated up much yet?
What fuel are you using? What spark plugs? Tuned?
No CEL. Have you scanned for codes? Any other recent issues?
I almost exclusively will fill up with Valero gas and always 92 octane.
I am not sure of the plugs and wires. I changed them several years ago around 85K miles (23K miles ago). This is only a recent issue that started about a month ago.
No tunes on the car at all other than a K&N drop in filter.
I will have to take note if it happens more often with a hot engine.
Senior Member
Joined: 12-05-2014
Posts: 3,330
From: Northern Ohio
Scan for codes, even tho no CEL. Write them down, noting if they are pending, current, or historic.
Since you don't know what plugs are in it, I would pull a plug in verify that they're the correct plugs and evaluate the condition.
See if you can get a bore scope in there and get a look at the valves.
Should have asked if you have an RPD. If so, set it to monitor the spark advance and see if it's rolling back to spark when you're having the problem. If no RPD, do it with a scan tool. I have used a Bluetooth dongle and the Torque app for this.
Since you don't know what plugs are in it, I would pull a plug in verify that they're the correct plugs and evaluate the condition.
See if you can get a bore scope in there and get a look at the valves.
Should have asked if you have an RPD. If so, set it to monitor the spark advance and see if it's rolling back to spark when you're having the problem. If no RPD, do it with a scan tool. I have used a Bluetooth dongle and the Torque app for this.