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GP- weird problem :-(

Discussion in 'Engine Compartment' started by abhinav7373, Dec 4, 2012.

  1. you One more thing about which I am highly disappointed. If the throttle body is at fault then it has to be replaced and it cant be repaired. Whole damn throttle body is sealed and no sensor can be taken out or cleaned or replaced.. Even if throttle position sensor goes bad whole throttle body will be replaced. and the price of throttle body is close to INR 27000 :A .. When i was told this I was like "Is it some sort of a damn joke!! " . I showed this problem to another mechanic who is a very good mechanic and deals only with the electrical in car he told me that 99.99% it is the throttle body only or if i am lucky it might be the accelerator paddle potentiometer. I really dont understand why fiat has put this kind of part which is so costly and even if a small sensor fault comes whole damn thing has to be replaced.

    - - - Merged Post - - -

    Karan does your car used to stall also few times??? Did you find solution to this problem?? does your car used to behave like this in petrol mode also?? My car is fine when ac is on but problem gets severe when headlights are on. Karan have seen the video which i have posted in this thread? have a look at that video and tell was ur problem similar to this one?
    Last edited: Jan 1, 2013
    1 person likes this.
  2. Now I understand why Fiat has failed in India even being the one of the early times automobile company. Fiat has given part (I am talking about Throttle Body here) which is similar to the one which comes with few Mercedes. And for a guy driving Mercedes 27000 bucks might not be a big deal but for a guy driving regular sedan or hatchback 27000 matters for this little thing and all other cars in this class have got parts which can be repaired by replacing one or more component of the part. The mechanic told me if it would have been any other car he might have tried sorting out the problem by replacing sensors inside the throttle body which is not possible with the fiat!! darn!! :A
  3. Italia-Linea

    Italia-Linea Staff Member Janitor

    Messages:
    2,123
    Pune
    Abhinav, Fiat has given you a very good technology. Now you have converted it to CNG and then this problem started. On petrol you dint face these problems.

    Not only fiat, i had to change the throttle body on my maruti alto. Same case, change the entire throttle body - Rs.17000. Take this. Same is the case on honda city and many other cars.
    The throttle body has IAC valves and sensors which have a perfect angled calibration. This calibration is done by using a potentiometer/scanner in service centre which is set for particular voltage . The angle is adjusted in such a way that this voltage is within the range. Only then your car will idle properly and maintain correct rpm to varrying load.

    Apart from this throttle position sensor is also calibrated ones. If your local mechanic says he will remove sensors are fit them, and if he doesnt have equipment to calibrate these sensors then boss its going to waste your money and lead to more trouble.

    Now i think you should keep your mind cool and we can try to solve your problems, cheers :)

    - - - Merged Post - - -

    Well i went through your entire thread and saw the video as well as Scanner codes. I check the documentation on the scanner too.

    1. The injector codes- P0202 means that the PCM detected a fault in the injector or the wiring to the injector. It monitors the injector and when the injector is activated, the PCM expects to see the voltage pulled "low" or close to zero. When the injector is switched off, the PCM expects to see a voltage that is close to battery voltage or "high". If it doesn't see the expected voltage the PCM will set this code. The PCM also monitors resitance in the circuit. If the resistance is excessively low or high it will set this code. (copy pasted)

    The symptoms for this code will likely be a misfire and a rough running engine. Poor acceleration. The MIL will also be illuminated.

    The causes of a P0202 engine light code could be any of the following:
    Bad injector. This is usually the cause of this code but doesn't rule out the possibility of one of the other causes
    Open in the wiring to the injector
    Short in the wiring to the injector
    Bad PCM


    2. P0638 - What does this mean?
    OBD Code P0638refers to
    The Powertrain Control Module (PCM) compares the actual Throttle Possition (TP) with the target TP when the engine is running. If the difference is more than the specification, the PCM determines that there is a throttle actuator control circuit range/performance problem.
    Symptoms
    Possible sumptoms of OBD code P0638
    - Engine Light ON (or Service Engine Soon Warning Light)
    Causes
    Possible causes of OBD code P0638
    - Drive-by-wire control system malfunction - Throttle actuator malfunction - Throttle valve malfunction - PCM malfunction


    With all the above study i think the installer messed up totally while fitting CNG.

    Now i can suggest yout the following.

    1. Remove the entire CNG connections. Make the car to bare stock.
    2. Reset ECU and Throttle body by removing the positive battery terminal and then putting in the key and trying to crank.It wont crank but residual current shall go.
    3. Check the voltages on Throttle Body.

    Since you have tried replacing other sensors etc i dont think there is any problem with those sensors. Now the last thing remaining is the throttle body. Clean it first. If IAC valve is stuck it cases idling and fluctuating problems.
    4 people like this.
  4. Thnx Italia-Linea for your reply. Well, I was very upset that is why wrote these things but yes if not all few things which I said were unfortunately true. Anyways, I am too a fan of fiat that's why I bought this wonderful car going against the will of my family, relatives and friends.

    "Abhinav, Fiat has given you a very good technology. Now you have converted it to CNG and then this problem started. On petrol you dint face these problems. "

    I agree fiat has given us superior technology and I think CNG installation did not do anything wrong but the installing a Timing Advance Processor was a bad decision.

    "Not only fiat, i had to change the throttle body on my maruti alto. Same case, change the entire throttle body - Rs.17000. Take this. Same is the case on honda city and many other cars."
    I agree to this point also but my point is the whole throttle body is sealed and no components can be replaced or repaired in it which is definitely not the case with any other Japanese car. If the throttle body is complete damaged then it a different case but if some sensor has gone bad then I don't think going for a whole new throttle body is a wise decision.

    "Apart from this throttle position sensor is also calibrated ones. If your local mechanic says he will remove sensors are fit them, and if he doesnt have equipment to calibrate these sensors then boss its going to waste your money and lead to more trouble."

    I think you are aware that I got TAP installed in my car which is connected with TPS wire and Crankshaft Position Sensor (CKP) of the car. The TPS wire was cut and a wire of TAP was joined with it. Do you think this procedure could have disturbed the calibration of the TPS? Is TPS is calibrated using OBD provided by FIAT?? If not then what is the tool?

    "Now i think you should keep your mind cool and we can try to solve your problems, cheers "

    Yeah I am feeling better now ... :) thnx for helping me out of this issue :) cheers..

    "Well i went through your entire thread and saw the video as well as Scanner codes. I check the documentation on the scanner too.

    1. The injector codes- P0202 means that the PCM detected a fault in the injector or the wiring to the injector. It monitors the injector and when the injector is activated, the PCM expects to see the voltage pulled "low" or close to zero. When the injector is switched off, the PCM expects to see a voltage that is close to battery voltage or "high". If it doesn't see the expected voltage the PCM will set this code. The PCM also monitors resitance in the circuit. If the resistance is excessively low or high it will set this code. (copy pasted)

    The symptoms for this code will likely be a misfire and a rough running engine. Poor acceleration. The MIL will also be illuminated.

    The causes of a P0202 engine light code could be any of the following:
    Bad injector. This is usually the cause of this code but doesn't rule out the possibility of one of the other causes
    Open in the wiring to the injector
    Short in the wiring to the injector
    Bad PCM "


    Well, I dont think there is any problem with the injectors as the problem persists even if the car is on CNG (At this time petrol injectors are non functional)

    "2. P0638 - What does this mean?
    OBD Code P0638refers to
    The Powertrain Control Module (PCM) compares the actual Throttle Possition (TP) with the target TP when the engine is running. If the difference is more than the specification, the PCM determines that there is a throttle actuator control circuit range/performance problem.
    Symptoms
    Possible sumptoms of OBD code P0638
    - Engine Light ON (or Service Engine Soon Warning Light)
    Causes
    Possible causes of OBD code P0638
    - Drive-by-wire control system malfunction - Throttle actuator malfunction - Throttle valve malfunction - PCM malfunction "


    All the codes were intermittent and were removed by the OBD. When I asked the mechanic he told me that there is nothing serious about the intermittent type of errors as they come when any sensor is plugged out with removing the -ve of the battery and ECU stores this. And next time when he connected the OBDit didn's come up with any error. He also told that if some permanent errors were present then some sensors would have been replaced. Even my mechanic (not TASC) told me that problem is likely to be with the actuator as it come into role when car is reaching towards idle and if it goes bad problems at low rpm may occur.

    "With all the above study i think the installer messed up totally while fitting CNG."

    Might be possible :(

    "Now i can suggest yout the following.

    1. Remove the entire CNG connections. Make the car to bare stock.
    2. Reset ECU and Throttle body by removing the positive battery terminal and then putting in the key and trying to crank.It wont crank but residual current shall go.
    3. Check the voltages on Throttle Body. "


    1. Already done but still everyone is clueless why this problem is occurring. No permanent error codes on OBD :confused:
    2. Done after ur suggestion but no improvement. :irked
    3. How can i do that??

    "Since you have tried replacing other sensors etc i dont think there is any problem with those sensors. Now the last thing remaining is the throttle body. Clean it first. If IAC valve is stuck it cases idling and fluctuating problems."
    Throttle body was cleaned twice by the service centre guys and I can now say the problem has become worse dont know why!!

    Few more things which both the mechanics told me is that My car's engine is missing at idling. There is periodic vibration in it. Can a bad throttle body make car's engine miss fire at idle??

    I am uploading a new video of what car does when i tap the accelerator in neutral with headlights switched on. U can see the illumination getting dim for a fraction of second and then coming back to normal. Have lok on Tachometer Needle also. Please guide me what should i do next..
    Last edited: Jan 5, 2013
  5. gurjinder

    gurjinder Staff Member Janitor

    Messages:
    3,989
    Punjab
    That is a huge red flag. Cutting wires of the TPS. :confused:

    Who knows if the TPS got fried right after the install. With the symptoms of your car pointing to a faulty TPS and that too right after installation of TAP, i reckon your TAP installer owes you Rs. 27000/-.

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