# Crank and cams timing verification and OBD errors?



## vwsal (Feb 16, 2011)

(my actual questions at the end of this post) 

Recently I purchase '02 GLX and before driving it did timing belt with everything that goes with it. 
I really can't compare to what it was like before belt change. 

I don't have any OBD errors, it idles very stable, very drivable and comfortable, it passed inspection without difficulty. When under load it sounds little deep but very even, almost like sport tuned exhaust. There is no holes in exhaust at all. 

Now when I feel safe with new belt I'm going through paces and finding that my engine does not behave the way I expect 2.8L should. My major issue is excessive engine (firing frequency) noise that getting x3 louder at ~3500RPM and with noise - loss of torque, maybe half of tprque above 3500. I already exclude intake changeover as it happened at 4700 and I also tried to disconnect valve deactivating intake change - no difference. 

Now my suspects are valves/cams timing. It also correlates to valve timing change, supposed to be at 3500. 

I've tried to disconnect cam adjusters - excessive noise moved up in RPM range and become a little quieter but still there. Torque become flatter through whole range bit less than with cam adjusters connected. 

I reconnect passenger side adjuster and drove around with just driver side disabled for a while. On third engine start I got P0021 (left side cam too advanced). Pretty sure it is related to my experiments. 

*The questions are:* 

*1. What are the OBD thresholds for cam timing errors? 

2. Will error of 1 tooth trip OBD? ( I guess it's same question as above) 

3. What are advancement angle for cam adjuster? 

4. When cam timing adjuster valve not powered or disconnected - is it advanced (idle and high RPM) or normal (mid range)? 

5. What are factory tolerance for cam timing set angle variations? 

6. On which cams cam positions sensors are mounted to, intake or exhaust? (I should be able to figure it out myself)* 


Greatly appreciate any help! 

Cheers!


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## O_o (Nov 12, 2009)

1,2: I don't know what the actual threshold level is, but one tooth off will throw a code. However, so will disconnecting the VVT. 

3. I really have no idea. 

4. Normal. You have the other part backwards though: it is advanced in the mid-range. 

5. In terms of angle, I don't know, but they almost never line up exactly, so something around 1/2 tooth's worth. 

6. Intake.


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## vwsal (Feb 16, 2011)

, 

Thank you for explanation! I did check and you are right about angle advancement in mid range. 
Should I assume that one full tooth in either direction will trip OBD? And because My car normally does not have any codes, can I be sure that I did not screw-up my belt job? 

If answers for all of the above are "yes" then my next questions would be: 

7. The best of my understanding cam adjuster powered only in mid range to advance intake timing. How does cam adjuster returns to normal (unpowered solenoid) position? Is it pushed back by oil redirected by solenoid valve or is there a spring or just by chain tension? 

8. Intake changeover - as I don't register any change in sound of the engine or performance when manually locking vacuum solenoid in either position or disconnecting it, should I suspect something with changeover valve? What can be bad there? Is it difficult to open and check or repair? 

9. What else can cause sudden (rather fast increasing with RPM from 3500 to 3700 by ~x3 times) excessive noise at firing frequency above 3500 RPM and simultaneous loss of ~half torque? When engine cold this sound increase is not as obvious, Torque decrease is about the same. 

Again, greatly appreciate any help! 

Cheers!


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## O_o (Nov 12, 2009)

7. VVT works hydraulically through the cam chain tensioner. The solenoid allows hydraulic pressure on one side or the other to move the whole tensioner up or down, which shortens or lengthens the tension side of the chain. 

8. I'm not really sure how the runner switch over works, but it's not supposed to do anything until 4,000 rpm or more, so I'd be surprised if that had anything to do with your problem. 

9. Usually, when an engine falls on its face like that, I suspect a fuel problem or blocked exhaust. I would think either of those would trip at least one code though. However, you did also mention something about a different exhaust sound in the OP...


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