Been troubleshooting some loss of power and intake popping sound issues for the last month. Got some intermittent cylinder misfire pending codes, tuned up with kingsborne 8mm wires and Bosch plugs which got rid of those.

Then continued to get a pending P0340 code (camshaft position sensor signal error fault). Same symptoms as before...power loss, popping into the intake. Picked up a used one, cleaned the connector with CRC electric cleaner and replaced with some dielectric grease.

Talked to a local mechanic who recommended tracking short and longterm fuel trims, so I added those to my Ultragauge. I was finally able to catch the problem on video.


Any thoughts on where to start digging? I've read and heard from multiple folks that the camshaft position sensor rarely fails so I'm not sure where else to go.

 

And some people say the U-G is a waste of money...

How are the O2's?

 

Didn't even think about it. Added both banks to the UG...will see if I can replicate it. Will report back.

 

Success! Finally a CEL for the P0340! Everything to this point has been pending, which is annoying as...

It took about 5 minutes of normal driving before the symptoms started to return. Uploading the video now, but from the looks of it when I'm on the throttle it short term fuel trim starts going way negative (-10) and O2 voltages drop to 0.015 from 0.9 at idle.

So if I'm looking at this right...when I'm under load and asking the engine for fuel something is telling it to hold fuel (negative STFT) which is reflected by the lean readings from the O2 sensors (low-voltages)? How does that even work?

From the rave:
And I'm easily detecting this as the driver.

Edit: From UG
So negative STFT means the computer is seeing rich conditions and is trying to pull fuel. But if it's running rich, I would expect to see higher voltages from the O2 banks, right? So confused...

 

I know almost nothing about fuel trim.
The O2's are supposed to change voltage as the engine is running, they are supposed to change voltage quickly, slow change in volts means slow response which will mess with the fueling of the engine.

 

I love these Barney style videos. Adds nothing but confusion to this situation since I'm not getting any lean or rich codes.

 

ummmm... P0340 is camshaft position sensor problem, and may not be associated with the O2s at all. There is a separate monitoring system for the CPS. See page 59 of attached GEMS ECU manual. Other codes are explained in depth as well.

You can unplug the cam shaft sensor and engine should still run with fall back values (unlike the crank shaft sensor). So you could repeat test with sensor off, it makes a code, but then see if problems are still there or other values are changing the way you think. I would suppose if the CPS is drifting all over the place, the ECU might try to correct the fueling.

 

Thanks Savannah. I've been going over that document. Trying to piece together the information (like I would for a patient in clinic) and nothing jives. I'm gonna pick up a vacuum gauge kit and see what's up, and measure the MAF outputs. If I'm measuring short term fuel trim, vacuum pressure, MAF and O2 sensor outputs on the 8 windows on the UG at least I'll be reading everything I can in relation to air and fuel in the engine, short of fuel pressure under load.

I'm sure I would be fine just replacing things that are old and need to be replaced anyway (ie. fuel filter), but for whatever reason I'm being super stubborn about trying to diagnose directly to get an answer.

Thanks for the input guys. Let me know if there's anything else I should measure/monitor.

 

Speaking of used CPS, the D1 GEMS uses a two pulse per rotation unit, and the D2 Bosch uses a four pulse per rotation unit.

 

And if signal from CPS is "wandering" - that could indicate a slack timing chain.