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  #13  
Old 09-29-2014, 11:36 PM
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Re: knocking engine detection

To start with the knocking sound, that can be a lot of things. Is it a loud knock, or more a kind of a ticking?
How is the engine running in general? Is it smooth in idle and at speed, or rough?
You saw that the STFT was quite ok at idle, but went up a lot at 2500 rpm. You will have to watch the STFT at a stable rpm, because during (smooth) acceleration or deceleration the figures will change a lot.
That the STFT went up at higher rpm, should mean that the problem is not vacuum related. A vacuum leak will have a much bigger effect at idle (small airflow) then at higher rpm (high airflow, so a leak has less effect).
Ofcourse it is nice to know what the problem is not, its even better to know what it is. The MAP figures seem to be ok as well.
So what is left is a low fuel pressure or a cylinder which doesnīt burn well .With a too low fuel pressure, not enough fuel will be injected (with the same injector opening time) and the O2 sensor will see a lean mixture. The PCM will try to compensate for that, by increasing the injector opening times and the STFT and subsequent LTFT will go up. Low fuel pressure will have less effect at idle (with low fuel flow), then it will at higher rpm.
So i would check the fuel pressure at the fuel rail with engine off, but also with engine running. The problem could be a clogged fuel filter, a bad pressure regulator (both are in the same housing and are mounted at left side/above rear axle) or a weak fuel pump.
Also check the plugs for fouling and gap.
A cylinder which is not burning well, will have more O2 in the gasses and can give a lean signal to the O2 sensor. The plug colour should be a tell tale.
Did you write that well, 0.06-0.08V at the O2 sensor?

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  #14  
Old 10-02-2014, 06:22 PM
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Re: knocking engine detection

Sorry for late answer, o2 sensor is not fluctuating when truck is hot. do you think that the main problem is a broken cylinder ? Which is making the noise? And burning the o2 sensor?


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Old 10-02-2014, 06:23 PM
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knocking engine detection

Sorry it is a ticking sound and
It is a smooth at driving and idle

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  #16  
Old 10-02-2014, 06:35 PM
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Re: knocking engine detection

A ticking sound can be from a hydraulic valve lash adjuster or several other things.
That the O2 sensor voltage doesnīt change while driving, could be a sign that there is no change in the fuel mixture. Did you write it down right, that the O2 was stuck at 0.08 V? It would correspond to the lean message at least, because there is too much O2 in the gasses.
I would still first check (or let someone check) the fuel pressure at the fuel rail. If that is too low, then you will end up with too little fuel (lean mixture) and the PCM will try to compensate with a possitive STFT. (and after a while the LTFT will follow).
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Old 10-02-2014, 06:43 PM
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Re: knocking engine detection

Yes I wrote right , o2 sensor got stuck in 0.8 in driving conditions. What is the correct fuel pressure in this truck? Should I change fuel filter to make sure is not clogged?


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  #18  
Old 10-02-2014, 07:09 PM
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Re: knocking engine detection

Quote:
Originally Posted by rocaloro View Post
Yes I wrote right , o2 sensor got stuck in 0.8 in driving conditions. What is the correct fuel pressure in this truck? Should I change fuel filter to make sure is not clogged?


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He, now you say 0.8V, but before 0.08V. What is the right figure?
The fuel pressure should be around the 45 PSI. There are two fuel filters and a pressure regulator, one filter at the bottom of the fuel pump module and the other is a filter/pressure regulator in one housing, mounted just in front of the rear axle. You could change the filter/pressure regulator and see, it is quite cheap. Only not allways that easy to remove the connections on the filter.
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  #19  
Old 10-02-2014, 07:24 PM
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knocking engine detection

Ok. I'm in the truck with the scanner hooked up. LTFTRM is 0.0 and the truck has been idle for 10 minutes. After 10 minutes it started to vary.
O2 sensor #1 is on 0.580, 0.600, 0.540, 0.360, 0.280, 0.080 and keeps switching.
O2 sensor #2 is on 0.160 and 0.140 only.
The knocking goes away for a couple minutes and comes back. The truck is now on a normal temp.

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  #20  
Old 10-03-2014, 11:55 AM
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Re: knocking engine detection

10 minutes before starting to vary is too long. On my jeep in less then a minute the O2 sensor is heated up and it runs in closed loop. You also better look at the STFT, because that is what the trim does at the moment you look at it.
Do you still smell fuel when at idle?
Will you change the fuel filter/pressure regulator first?
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  #21  
Old 10-03-2014, 01:24 PM
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Re: knocking engine detection

Strong gas smell at idle always. I will change fuel filter and let you know. Spark plugs looks ok. I made oil change and found with a magnet little pieces of metal ,but just a few they look toasted.


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  #22  
Old 10-03-2014, 02:24 PM
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Re: knocking engine detection

There is a writeup for the fuel filter change, but i canīt find it anymore
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