# Why does the diesel cruze have a throttle body?



## MP81 (Jul 20, 2015)

It's technically called a "throttle valve". 

I can't remember for sure what its purpose is.

On the deleted engines, it is supposed to be unplugged.


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## boraz (Aug 29, 2013)

its there for egr....its not connected to the skinny pedal

when you delete it, you unplug the electrical connections so it remains open

100% you can remove the whole body or the plate if you do wish...its not operational when deleted

you mention when you deleted, but dont mention kms since delete? 

delete tunes dont necessarily program the sensors to read zero, they read w/e will satisfy the computer to allow the car to putt along

whose tune do you have?

black smoke is an air leak in your intake, search that out


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## kelaog (Aug 1, 2019)

MP81 said:


> It's technically called a "throttle valve".
> 
> I can't remember for sure what its purpose is.
> 
> On the deleted engines, it is supposed to be unplugged.


^ thank you for your reply. I had a a wizard out here do the full delete and install for $1400 which was less than it would have cost me for the parts from OzTuner, so I went that route. I don't believe he unplugged the throttle body but he may have disabled it like I suggested. What I may do is unplug it first and see how the car acts, then remove the plate.


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## boraz (Aug 29, 2013)

check all your intake hose clamps, check the plastic intake at the throttle valve


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## kelaog (Aug 1, 2019)

boraz said:


> its there for egr....its not connected to the skinny pedal
> 
> when you delete it, you unplug the electrical connections so it remains open
> 
> ...


I had a local guy here do the tune and delete. He fabricated the down pipe, installed, and tuned for less than the parts most of the guys here bought. 

I've put about 25,000 km since the delete on. It worked well until just recently. I recall at the time I had a CEL on for the EGT and he disabled it which explains why I'm not getting a light. I don't believe that's impacted performance.

I believe you're suggesting that I have a boost leak on the pressure side of the piping. I suspected that as well but I assumed it would show up in the commanded vs. actual boost trend unless its very minor. I could be wrong. I'll have to build a pressure testing rig.


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## boraz (Aug 29, 2013)

kelaog said:


> ^ thank you for your reply. I had a a wizard out here do the full delete and install for $1400 which was less than it would have cost me for the parts from OzTuner, so I went that route. I don't believe he unplugged the throttle body but he may have disabled it like I suggested. What I may do is unplug it first and see how the car acts, then remove the plate.


your wizard will have your answers then, its his tune.

how many cruzes has he done? whats the most miles on them post delete?


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## boraz (Aug 29, 2013)

kelaog said:


> I had a local guy here do the tune and delete. He fabricated the down pipe, installed, and tuned for less than the parts most of the guys here bought.
> 
> I've put about 25,000 km since the delete on. It worked well until just recently. I recall at the time I had a CEL on for the EGT and he disabled it which explains why I'm not getting a light. I don't believe that's impacted performance.
> 
> I believe you're suggesting that I have a boost leak on the pressure side of the piping. I suspected that as well but I assumed it would show up in the commanded vs. actual boost trend unless its very minor. I could be wrong. I'll have to build a pressure testing rig.


smoke color doesnt lie...black smoke is too much fuel.....on a diesel that means too much air and/or the car thinking it has too much air...but start simple and eliminate the obvious-physical intake air leaks

yeah, could be injector timing, or injector leak....they havent been an issue on others cars yet though


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## Snipesy (Dec 7, 2015)

It doesn’t do anything except in regens. Even then it’s not much. Normally the only action it sees is a short self test when you turn off the vehicle.

It’s also suppose to stop runaways but I’m not sure how successful it actually is in that regard.


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## kelaog (Aug 1, 2019)

Snipesy said:


> It doesn’t do anything except in regens. Even then it’s not much. Normally the only action it sees is a short self test when you turn off the vehicle.
> 
> It’s also suppose to stop runaways but I’m not sure how successful it actually is in that regard.


Considering it appears to be fail open, i wouldn't assume very successful.I was trending the throttle position yesterday over time and when the key is off it opens and closes rapidly a few times. If it were to remain closed, it would be pretty successful at stopping a runaway if the owner were to turn off the car (probably most peoples first intuition when panicking).

I'm not sure if anyone else has the ability to datalog but if you do would you mind trending a few things for me and seeing what your normal values are?

1. throttle position is 84% from key on to key off. My car is deleted obviously.
2. O2 sensor voltage appears to be flat at 0.2 volts with minor fluctuations I don't have a high enough resolution to see. I actually think this is actually reverting to a closed loop tune and running like crap on the delete. That or it's constantly showing a lean condition even when the car shoots a black cloud. In my experience with gasoline cars these trends usually look like an eratic squared sine wave with values between .1 and .9. But I know typically diesels run much leaner mixtures and the absence of a throttle plate would make the lean condition more consistent, can anyone confirm?

Things i've ruled out
1. EGT Sensor #2. I was about to replace the EGT sensor #2 but upon opening the hood it looks like my down pipe excludes it. I found the connector empty. I now know this is not the issue and the value of 1000C is the maximum range of the ECU for that sensor. IE: this is probably not the issue. I'm pretty sure it's a boost leak, or the O2 sensor causing me issues.
2. MAP SENSOR the barometric pressure reading I'mgetting is valid. I'm just an idiot. FYI: if you were to use the weather network in colarado and look at the barometric pressure reading they provide; it is actually compensated to sea level so it will be much higher than reality. Most meteorologists would refer to this as the 'Sea Level Pressure'. The weather network does not think it's important to use the real definition or at least explain their pressure value. LOL. I'm embarrassed to state what my profession is after this royal f'kup.The MAP was still very dirty and I'm glad I took the effort to clean it. It also acts as the intake air temperature sensor on this car and when dirty will still work but respond much slower to changes in the manifold.

Remaining 
1. Boost Leak (waiting a leak test)
2. O2 sensor (need to confirm expected values but I may just replace the sensor)
3. Throttle position  at 84% instead of 100% (If 1&2 check out this might still be an issue but wouldn't explain the rich condition at low throttle). It's more likely that the potentiate needs calibrating and is actually at 100% open but reading 84% based on the fail position.

I'm pretty sure it's either the O2 sensor or a boost leak at this point but my charge air piping looked pretty good and all the clamps were tight. I'm just writing down my trouble shooting philosophy in hopes someone else can follow it if they are having similar issues down the road.


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## TheRealHip (Sep 1, 2014)

That's odd your down pipe doesn't have EGT Sensor #2. There should be 4 screwed into it.


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## Snipesy (Dec 7, 2015)

It’s not hard to remove the pipe and have a shop add new sensor bungs. I think you just need 3.

All my deletes have everything plugged in by default. Including the throttle valve, egr, etc.. The less tampering the better really. The O2 sensor in particular is insanely useful even on a delete.


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## MP81 (Jul 20, 2015)

It makes sense - you have the sensors, you really would be best to use as much input as possible...


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## kelaog (Aug 1, 2019)

Update on this:
I went to replace the o2 sensor and had mistaken the nox sensor as the o2. I do not have an o2 sensor anymore. I’m ruling that out. 

I checked the throttle body out and it was somewhat sooty but not nearly as bad as I’ve seen on here. It was 100% open although the reading is still 84%. There must be a way to calibrate it. The bolts were pretty loose so I tightened them up. I don’t think this was my issue. 

Lastly I changed the fuel filter after. Many of my symptoms are related to bad fuel filters and it seemed to come and go which a boost leak typically would not do. After changing the fuel filter my power is back and the idle sound became much cleaner. 

So far so good but I’ll give it a few days of running around before calling it good.


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## MP81 (Jul 20, 2015)

Was your intercooler charge pipe loose? That's been known to happen - if your throttle body was loose, you could have had unmetered air coming in that way as well.


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## kelaog (Aug 1, 2019)

MP81 said:


> Was your intercooler charge pipe loose? That's been known to happen - if your throttle body was loose, you could have had unmetered air coming in that way as well.


Hmm it's possible I suppose. The clip that holds it on isn't very robust or leak tight IMO. Perhaps it was leaking and the removal and re-installation reseated it properly. The bolts weren't finger loose or anything but warranted an extra 15 degree turn on each bolt with my highly calibrated torque meter (arm).

Unmetered air coming in wouldn't have much ill effect on a diesel, but metered air escaping certainly would. In my experience, this was probably a combination of issues from a dirty MAP, to a slightly loose charge air connection and a dirty fuel filter.

Thanks all for your help. I hope I can return the favour when you need it. It sure was nice to pass in 6th gear with authority again on my commute this morning. Fuel economy has returned as well.


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## kelaog (Aug 1, 2019)

Following up on these problems. I had thought it was a dirty fuel filter, but we had a pattern of cool weather following the filter change. The symptoms were not as noticeable when the ambient temperature dropped below 18 celcius; however, after a short week of cooler weather our typically hot days (30C+) returned and the car began acting up again. I actually noticed that the engine timing would retard to negative timing when it was hot out which explained the lack of power and extra smoke.

I took it back to the tuner to run some more diagnostics. He couldn't see anything physically wrong, or anything wrong with the tune that would cause the symptoms I was having. Alas, he figured perhaps something in the exhaust was plugged and put a pressure tap where the NOX sensor would normally sit.

As it turns out the SCR was almost completely plugged. When we removed it and held it up end to end against the sun only a hole 1/4" in diameter was visible end to end. You might be wondering why the car was deleted and the SCR remained. Typically you can leave them alone with a clean enough tune.

After the SCR was removed, the car was back to full power and I averaged 3.9 L/100 km on the way home doing 110 kph. Wow! It's a bit louder but cruzing speeds isn't really noticeable. 

Just posting this in case someone one day has some similar temperature dependent issues and needs help tracking it down. 

Cheers!


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## Rivergoer (Mar 30, 2017)

Would love to see a pic or two of the plugged SCR.


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