1az-fse 2004 Toyota Noah running rich

Darren Fraser · Post by **Darren Fraser** » Fri Oct 23, 2020 9:19 pm

Not sure if any of you have been following my thread on Iatn regarding this vehicle.

In a nutshell we have a rich condition on this vehicle STFT -20 at idle and O2 maxed out at 850mv. STFT and O2 improve slightly at 2500-3000 rpm.

The engine is a speed density engine using only a MAP sensor for air measurement and control. The idling is high (1200rpm) and vacuum is sitting around 16.8 inches/Hg. (We've had a huge debate about the vacuum and MAP readings on Iatn because I am 1300m above sea level and barometric pressure at sea level (which most guys are used to) are a lot more than what we have here. However, it would appear that this engine is suffering from a low vacuum/MAP pressure condition. There's also been a huge debate about how speed density engines react to vacuum leaks. Some say that a vacuum leak will cause negative fuel trims and others say it won't.

We've checked all possible areas for external vacuum leaks and found none. So we're looking at timing/valve issues that may be limiting the engine in producing adequate vacuum.

Some recommendations were a stretched timing chain, and over skimming of the cylinder head causing excessive slack in the timing chain.

When I scoped the CAM/CKP to check cam crank correlation I came up with a really weird CAM signal. It's nothing like the known good that I took off of a known good vehicle.

The "humps" I saw, I initially thought was CEMF feedback from injectors/ignition but they were only common to cylinders 1&4. The effect of cylinders 2&3 were minor ripples in the CAM signal.

I hope the images I've saved are able to load on this thread, and I would appreciate your thoughts on these wave forms if you've encountered a similar problem.

Thanks again for an awesome community.

Darren Fraser · Post by **Darren Fraser** » Fri Oct 23, 2020 9:21 pm

So my thoughts are that the humps and ripples in this CAM signal (red) is actually backlash of the camshafts cause from a slack chain? Would you agree?

Darren Fraser · Post by **Darren Fraser** » Fri Oct 23, 2020 9:42 pm

The other images with the red Hall effect waveforms are actually ignition COP triggers so I could see where my ignition event was happening in relation to the Cam and CKP signals. It looks like I'm retarded if I'm taking the falling edge of the trigger as my firing event? Unfortunately a cant measure secondary spark (yet) because I'm waiting for our new Pico system and Pressure kit to arrive (can't wait!). I couldn't get a primary wave either because the coils have a diode built in so I can't see secondary.

This was the relative compression using the trigger on coil number 1.

liviu2004 · Post by **liviu2004** » Sat Oct 24, 2020 9:49 pm

You know Bernie from ATS? He has a youtube video where he shows that the ckp sensor extra hump on rising edge is actually bad. Should of been a continuos rise. Check out his videos.

Darren Fraser · Post by **Darren Fraser** » Sun Oct 25, 2020 5:19 am

Thanks. Do you have a link to that video? I'll try and find it.

liviu2004 · Post by **liviu2004** » Sun Oct 25, 2020 7:33 am

https://youtu.be/A561r9n8HzM

Put your channels in DC mode btw.

Darren Fraser · Post by **Darren Fraser** » Sun Oct 25, 2020 9:40 am

Thanks for the link. Quite an eye opener! Even though Bernie was looking at the CKP sensor U can so see where he is coming from.

It looks like my PCM could be firing on the first hump of my CAM signal and using that to calculate timing?

Darren Fraser · Post by **Darren Fraser** » Sun Oct 25, 2020 9:41 am

Forgot to mention, I have access to a donor vehicle which I plan to capture a known good CAM/IGN trigger.

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