Poor throttle performance

[Benjamin]

I have my brothers 2003 Buick Century and its been having some issues, typically with how rough it sounds when getting to higher RPMs..

I plugged in the scan tool and I had codes for “Cylinder 1 misfire” and some “Thermostat” error, and multiple codes for the EGR and one for an EVAP leak.
So I decided to start by replacing the spark plugs, everything by the book(Crouched down atop the engine frame to get to those pesky 1,3,5 cylinders, gotta love the 3100 SFI)… All said and done, I plugged in the scan tool erased codes, and re-scanned.

For whatever reason, I’m now down to 1 DTC for simply replacing the spark plugs(P0405-Position Sensor Circuit Low Voltage) :dry:.

The change didn’t seem to fix what I had hoped, when getting to 30mph and anything above it makes a loud humming noise and almost feels like all the brakes are seized up… very slow response.

Started the car up, looked under the bonnet, and removed electrical connections pertaining to the throttle body-while revving. I didn’t notice any major changes but came across some questionable areas….

The “PCV hose” is deteriorated and I noticed it pinches shut after some time with the engine running.

Checking the TPS sensor, it seems to have oily residue residing in the connections… From what? I don’t know, but I think it may have to do with my problem.

Could I have found the issues?

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Topic

[college man]

Could be the cause. Clean the sensor and plug connection with brake clean
and clear the code and see what happens. I would imagine the pcv hose is
throwing oil vapor at the connector/sensor.

[Joe]

Hi

Dtc P0405 is related to the EGR Postion sensor not the TPS. Just wanted you to be aware If your checking the Throttle Position Sensor based on the P0405 the code is related to a different component on the vehicle? As far as poor acceleration are you sure you not having an issue with the egr? Let me know if you need more help. Happy to walk you through testing the EGR system on the vehicle. Also keep in mind you dealing with the DTC p0405 which relates to a low voltage problem on that circuit. The PCM monitors the EGR valve position sensor. The 5V, low reference, and signal wires going to the sensor are calculated by the PCM to determine EGR pintle position. If the EGR sensor signal is pulled below a certain voltage level the DTC P0405 will set and illuminate the MIL on your vehicle. On a different note the oil in in the TPS connector needs to be addressed too. Let me know if you need help.

[Benjamin]

Thanks for the reply.

Would the EGR have anything to do with the odd “humming” sound I get when accelerating to a higher speed? My brother said that he had the EGR valve replaced. It almost sounds like the parking brake is engaged(Which I know it is not). The vehicle just drags…

[Author]

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