Sarah29wv

Just as the title says. Idles fine, starts fine, no noticeable loss of fuel mileage. While driving, try to accelerate, especially when going up a steep hill on the interstate and it will jerk, RPMs will drop to maybe 1500 then it will raise to over 2000 and hold the current speed but does not feel like its strong enough to push to accelerate while climbing. It used to be, if I were going up the mountain, I could step on the pedal and it would roar, accelerate smooth, shift smoot, no issues. Now it feels sluggish, no power. I drive a LOT. We are building about 2 hours away and I travel back and forth at least once per week. We have a farm that has a very steep driveway as well. Not sure if this is fuel pump/filter related, transmission related, torque converter, or what. Any suggestions so we can start working on it would be good.

strutaeng

Is the Service Engine Soon light on the dash on? Scan it for codes.

Better yet, hook up a scanner that has live data stream. Look at the fuel trims for bank 1 and 2. Fuel delivery will almost always show up as lean condition on BOTH banks.

Look at other data like speed, RPM, coolant temperature, etc. and confirm that it matches what your dash is showing.

1FastBrick

iTrader: (17)

I Suggest you tell us a little more about what your working.

Year? Milage? Has any of the major maintenance been done or kept on?

Sarah29wv

I've had the truck for about 3 years now. 2004, about 287,000 miles on it. Regular maintenance is done since I've owned it. Replaced quite the list of parts on it since I've bought it. - Alternator, radiator, transfer case, power steering pump, idler pulley, tensioner pulley. Im sure there's more that Im forgetting... We've also replaced things like ball joins. control arms, tie rods, pitman arm, shocks, spark plugs.

It does have a check engine light on, but it always stays on with this truck. The last time I checked the code it was the oxygen sensor, which we replaced, but the code keeps coming back. I'm going to have Advanced run a code diagnostics on it today.

strutaeng

On the O2 sensor, it was possible that the engine was not performing within the parameters, and the O2 sensor correctly gave a voltage code. Without knowing what to look for (or look at the O2 waveform on a scan code), it's easy to assume it's a faulty O2 sensor as misdiagnosis. Even so, the ECU can make slight adjustments for fuel trims within a certain percentage, if that was the case.

So you may not know know if something else has now failed because your SES light was already illuminated. Could be a lot of things. Check for codes is always the first step on these issues.

Sarah29wv

Had advanced run a code check and got back a few.
P0120: throttle position system performance
P0327: knock sensor circuit low voltage
P0332: knock sensor 2 circuit low voltage bank 2
P0442: evap emmissions system small leak detected
P2135: throttle position (tp) sensor 1-2 correlation

We're going to start with the throttle positioning sensor and knock sensor, hopefully that fixes it. Amy other suggestions?

strutaeng

Yeah, start with the throttle position sensor codes. That would definitely cause drivability issues. Check the wiring first. I think I read somewhere here the wiring near the connector is subject to fraying. Could be an intermittent loss of signal from a wire with corrosion or about to break. Don't assume it's the sensor until it can be confirmed.

The knock sensors codes I don't believe will cause a severe drivability problem? But probably need replacement if they are the original. Water gets down in there and they corrode and give those codes. Replace the harness as well. Watch a YT video that shows the little RTV dams to build around them on the valley cover.

EVAP code will not cause drivability issue. That one could be a challenge to resolve. Is rust an issue where you live? The vent valve is prone to failing up in the saltbelt region, along with all the other stuff corroding. Watch the WellTech channel on YT that explains EVAP operation on the GM vehicles. Could be a small leak on a hose, at the purge solenoid, gas cap, filler neck or the fuel pump locking ring. May require diagnosis with a smoke machine. I would fix this last on that list.
Good luck.

RDF1

My 2004 did very similar things.
I put a new AC Delco Throttle body on and it fixed all those issues. But that was after chasing wiring with out issues found, swapped TAC Module and still had issues. Only after putting new TB on that it was fixed.

Knock sensor codes will pull timing out and make truck feel very weak.
I have seen evap codes caused by the purge valve on the intake manifold. It was pulling gas fumes into the intake causing the oxygen sensors to show it was running rich.

shakenfake

knock sensor codes will only cause drivability if they are sensing knock. In my experience I ran with the knock sensor code and was not having any timing pulled until the event that was causing my knock.

RDF1

It will also pull timing on fast throttle transitions. If the knock sensor is water logged it will detect knock quite often even at idle.