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  • edithdavis77
    edithdavis77 - 1988 Pontiac 6000 - Transmissions & Drivetrains - 5/3/2013
    Why does the engine knock when I step on the gas?
    The car runs fine. It occurs each time I start the car and hit the accelerator.
     
    • Jimm
      5/3/2013 Jimm
      First step - check the engine oil level and refill as necessary. if the engine knock is related to fuel / spark knock - then here are some possibilities;

      Spark knock (detonation) is an erratic form of combustion that occurs when multiple flame fronts occur simultaneously inside a combustion chamber. Detonation occurs because fuel is subjected to either too much pressure, too much heat or both. It usually happens during acceleration when the engine is heavily loaded and cylinder pressures are at their peak.

      Instead of a single flame front growing outward smoothly like an expanding balloon from the point of ignition, multiple flame fronts are generated spontaneously throughout the combustion chamber as the fuel automatically ignites from heat and pressure. The multiple flame fronts collide, creating shock waves that produce a sharp metallic pinging or knocking noise.

      Mild detonation can occur in almost any engine and will not cause damage. Prolonged heavy detonation can crack pistons and rings, blow out head gaskets, damage spark plugs and valves, and flatten rod bearings.

      Any of the following can cause detonation:

      Too Much Compression: An accumulation of carbon deposits in the combustion chambers, on piston tops and valves can increase compression to the point where it exceeds fuel octane rating. If a top cleaner fuel additive fails to remove deposits, a new alternative is to blast the deposits loose by blowing crushed walnut shells through the spark plug hole. Otherwise, the head will have to be removed so the deposits can be scraped off.
      Overadvanced Ignition Timing: Too much spark advance causes cylinder pressure to rise too rapidly. If resetting the timing to stock specifications does not help, retarding timing a couple of degrees may be necessary to eliminate knock.
      Engine Overheating: A hot engine is more likely to suffer spark knock than one which runs at normal temperature. Overheating can be caused by low coolant, a defective fan clutch, too hot a thermostat, a bad water pump, etc. A buildup of lime and rust deposits in the head and block can also reduce heat transfer

      Overheated Air: The thermostatically controlled air cleaner provides the carburetor with hot air to aid fuel vaporization during engine warm-up. If the air control door sticks shut so that the carburetor continues to receive heated air after the engine is warm, detonation may occur, especially during hot weather. Check the operation of the air flow control door in the air cleaner to see that it opens as the engine warms up. No movement may mean a loose vacuum hose or a defective vacuum motor or thermostat.

      Lean Fuel Mixture: Rich fuel mixtures resist detonation while lean ones do not. Air leaks in vacuum lines, intake manifold gaskets, carburetor gaskets or fuel injection intake plumbing downstream of the throttle can all admit extra air into the engine and lean out the fuel mixture. Lean mixtures can also be caused by dirty fuel injectors, carburetor jets clogged with fuel deposits or dirt, a restricted fuel filter, or a weak fuel pump.

      The air/fuel ratio can also be affected by changes in altitude. A carburetor calibrated for high altitude driving will run too lean if driven at a lower elevation. Altitude changes are generally compensated for on computer cars by the barometric pressure sensor.

      A lean fuel condition can be diagnosed by watching for lean misfire on an ignition scope, or by using a four-gas infrared analyzer and watching exhaust oxygen levels. A reading over about 3% to 4% oxygen would indicate a lean fuel condition.

      Spark Plug Too Hot: The wrong heat range plug can cause detonation as well as pre-ignition. Copper core plugs are less likely to cause detonation than standard spark plugs.

      Loss of Exhaust Gas Recirculation (EGR): EGR keeps combustion temperatures down, reducing the tendency to detonate. If the EGR valve is inoperative or someone has disconnected or plugged its vacuum hose, higher combustion temperatures can cause pinging.

      Low Octane Fuel: Burning cheap gas may be one way to save pennies, but switching to a higher grade of fuel may be necessary to eliminate a persistent knock problem.

      Defective Knock Sensor: The knock sensor responds to frequency vibrations produced by detonation (typically 6 - 8 kHz), and signals the computer to momentarily retard ignition timing until detonation stops. A knock sensor can usually be tested by rapping a wrench on the manifold near the sensor (never hit the sensor itself). If there is no timing retard, the sensor may be defective.



  • www.robertmiles461
    www.robertmiles461 - 1999 Pontiac Grand Am - Transmissions & Drivetrains - 4/30/2013
    Just pull engine in last week.now when put in gear i have noise in it
     
    0 answer
  • ostermw
    ostermw - 2002 Pontiac Grand Am - Transmissions & Drivetrains - 4/12/2013
    While driving forward there is a noticable noice but when driving in reverse the noise will increase.
    The noice is only noticable while driving. the check engine light will start blinking and stay on.
     
    • k+dtrans+auto
      4/12/2013 k+dtrans+auto
      have it scanned for codes, address those first and see if problem is taken care of.
  • Michael
    Michael - 1998 Pontiac Grand Prix - Transmissions & Drivetrains - 4/2/2013
    What could be wrong when my cruise control doesn't work?
    I have checked all of the fuses and all of the other functions work with my turn signal switch. It has 125K miles now. I bought it when it had 100K and it didn't work then. Thanks, Michael
     
    0 answer
  • fatkidd84
    fatkidd84 - 1994 Pontiac Grand Am - Transmissions & Drivetrains - 3/23/2013
    When very hard on the gas pedal hits the rev limite and will not shift until slightly released why??
    On 94 Grand Am quad for motor 62,000 miles 2 guys at work think is a misfire. The transmission shift smoothly and strong . The fluid may or may not be original I do not know. I have done of full tune up it has new plugs boots cap and coils. Also has a new fuel line ...
     
    0 answer
  • coryb1384
     
    0 answer
  • josephgonzales_az
    josephgonzales_az - 2007 Pontiac G6 - Transmissions & Drivetrains - 3/23/2013
    My speedometer shows that i am going faster then i am
     
    0 answer
  • martinsowe
    martinsowe - 2003 Pontiac Aztek - Transmissions & Drivetrains - 3/8/2013
    I changed the top cylinder gasket on my car put It back together, the engine runs good but the gears will not engage
    The tranmission fluid was emptied but refilled again and when I started the engine and try to shift the gear IT MOVES to different positions but do not engage.
     
    0 answer
  • martinsowe
    martinsowe - 2003 Pontiac Aztek - Transmissions & Drivetrains - 3/8/2013
    I changed the top cylinder gasket on my car put It back together, the engine runs good but the gears will not engage
    The tranmission fluid was emptied but refilled again and when I started the engine and try to shift the gear IT MOVES to different positions but do not engage.
     
    0 answer
  • k.m.reichardt
    k.m.reichardt - 1995 Pontiac Grand Prix - Transmissions & Drivetrains - 3/3/2013
    Stuck in neutral to drive.
    Won't shift.
     
    0 answer
  • aliform9
    aliform9 - 2002 Pontiac Sunfire - Transmissions & Drivetrains - 2/24/2013
    My clutch keeps sticking and stick is hard to shift
    the stick is hard to shift when it is cold, but the clutch sticks everytime I shift gears
     
    0 answer
  • dkropf26
    dkropf26 - 2004 Pontiac Grand Am - Transmissions & Drivetrains - 2/17/2013
    My car just started giving me trouble. It will turn over but wont start. put gas into fuel injector yesterday and car
    started and problem seemed solved. Until today when it wouldn't start again, it acting like there is no gas . what can i do?
     
    0 answer
  • zaniyasylvester
    zaniyasylvester - 2002 Pontiac Montana - Transmissions & Drivetrains - 2/9/2013
    Transimission is alway empty
     
    • Jimm
      2/9/2013 Jimm
      Need more information - is there a question in regard to the 'transmission always empty' issue? Is there a question about how to repair? Please post a reply and try to rephrase the issue you are having in the form of a question for further assistance.
  • dlockley82
    dlockley82 - 2008 Pontiac Torrent - Transmissions & Drivetrains - 2/5/2013
    Can the front abs wheel speed sensor be replaced on a 2008 torrent awd?
    stock ac delco replacement hub doesnt come with sensors apparently so I assume it can be but just want to make sure
     
    • HouseCallAuto
      2/5/2013 HouseCallAuto
      Yes the sensor can be bought separately, however I would make sure that after removing the retaining bolt that holds the sensor in place, and then make sure that the sensor is not frozen in place, and then you can buy the sensor. If it were me, it is not worth the concern of finding this out after beginning work on the vehicle, and being that the sensor comes already installed in most brands of hub assemblies (ACDELCO is an exception) and the sensor is like $60 while the hub ass'y is like $120, for my money and time, I would buy the hub ass'y with a new sensor. I also believe that in many cases the hub ass'y is the cause of the fault code for the abs sensor to begin with.
      HouseCallAuto
      2/5/2013 dlockley82
      ok thank you. I actually dont have an abs light on but i need the hub assembly replaced...I am having a hard time determining which brands come with the appropriate sensor. Will the timken assembly come with the sensor? What about Centric or one of the more inexpensive brands? Any additional info would be much appreciated. Thanks
    • HouseCallAuto
      2/5/2013 HouseCallAuto
      yes, the Timken hub seems to come with the sensor , but in one picture I saw you cannot see a wire, however when I clicked add'l info I read this >> Features a pre-sealed, pre-greased and pre-set bearing package design with integrated sensing technology for anti-lock braking systems, total traction control and vehicle dynamics systems.
      Fully serviceable wheel speed sensor (where applicable) is internally mounted and protected from road hazards, debris and potential damage.

      I think they all come with sensors (except ACDELCO)
      HouseCallAuto
      2/5/2013 dlockley82
      Ya I read the same thing actually on rockauto.com. It is very confusing though because I was looking at an assembly from a cheaper brand on ebay that says it comes with all the sensors but then I emailed them and they said it didn't for my vehicle. The fact that its AWD shouldn't change anything should it? because most sites don't ask me to input that spec about my vehicle when they provide search results. Have you heard anything good about any of the "budget" brands of hub assemblies?
      HouseCallAuto
      2/5/2013 HouseCallAuto
      I'm OK with them. Have installed many of those "value" brands and if they were to have failed because of there little known brand '/ quality, I would have had a call back.
  • jdmhondaboy112
    jdmhondaboy112 - 1993 Pontiac Bonneville - Transmissions & Drivetrains - 2/3/2013
    How do you find out what typ of transmission is in a 1993 pontiac bonneville and if it does have traction control ????
     
    • Jimm
      2/3/2013 Jimm
      Check the VIN; code-L, = automatic transmission, FWD, option codes are listed below;

      FWD trac control (opt NW9) supercharger opt
      Without supercharger opt 2.84 ratio (opt F17)
      3.06 ratio (opt FW2)

      Without trac control supercharger opt
      Without supercharger opt 2.84 ratio (opt F17) 16" wheel (opt QNX)
      Without 16" wheel 3.06 ratio (opt FW2)

      Jimm
      2/3/2013 CVO
      See this transmission fluid for different applications.

      http://www.autozone.com/.../...ficationsMain.jsp
      Jimm
      2/3/2013 CVO
      Sorry, you didn't ask for the type of transmission fluid.
 
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