Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!





Chevy C/K Series Maintenance and Repair

1101113151623

Comments

  • myxjsmyxjs Posts: 3
    you mentioned the fuel pressure regulator, i have a 1985 jaguar xjs, and i am told i have bad fuel pressure regulators, i was wondering if you could tell me how to test these. zanecrockett@hotmail.com
  • dchase1dchase1 Posts: 15
    still cant figure it out.it is a cng bi fuel vehicle which makes it more confusing.bi fuel does not work .connections look good.brown wire going to alternative fuel box is broken where the two connectors go into box.hooked it up between the two connectors ran great for 20 miles but bi fuel doesnt work.shut it off .on the way home.ran real bad.took sensor back.installed another one.replaced distributor cap.could my distribitor be bad.is there suppossed to be play vertically where the rotor mounts?bi fuel was not working before problem.wire has not been hooked up since i had the truck.recently replaced driveplate.ran good afterwards.replaced starter.recent alternator.new ignition relay.oil change,fuel filter.still get code po 340 po340 po341.what is involved in the camshaft sensor circut?could a bad fuel pump relay cause this.is my computer fried?could just spark plugs cause this?vehicle sat unstarted for 3 months befoe driveplate was replaced.fuel pump?DIRTY TANK?fuel INJECTORS?CMon gotta be something stupid its a chevy not a ford.always ran good before.only has 60000 on it.idles fine,drives bad.lacking power.sucks on hills.i know its some electronic crap.gotta be.after you disconnect battery or clear code runs great for 10 miles.hit about 50 or 60 on slight incline i here a thump/backfire/miss not sure light goes on no matter what after 10 miles.driving me nuts.any one have similar exp. or know what is going on?helppppp.why does the camshaft sensor get no signal.i cant sleep my chevy is driving me nuts
  • dchase1dchase1 Posts: 15
    try horn relay in fuse box under hood.
  • dchase1dchase1 Posts: 15
    try brake relay in underhood fuse box
  • dchase1dchase1 Posts: 15
    u have to have it reprogrammed by the dealer
  • xwesxxwesx Fairbanks, AlaskaPosts: 8,276
    There has to be a sensor (separate from cam sensor) on that thing that detects the knock and tells the engine to retard the timing for pulling hills, acceleration, etc. I am still betting on it as being the culprit. Maybe I am way off base here - I have never fiddled with anything so new as a '97. :mad:
  • c130efec130efe Posts: 2
    Quick question...I have a 94 K1500 with a 305. The engine is shot and I was thinking of replacing it with a 350. Can anyone think of any issues or complications to doing this? Thanks
  • dchase1dchase1 Posts: 15
    wouldnt i get a code when i scanned it telling me it was the knock sensor.the sensors arent cheap.it does make sense,but the truck runs fine right after the idle is relearned for about ten miles.then all the bs starts.lack of power,vibration while at idle.could this be a dexcool issue?i dont know.something electronic i think,hard to figure out.all wiring seems ok.wierd ver wierd.
  • xwesxxwesx Fairbanks, AlaskaPosts: 8,276
    Well, I have had to replace the knock sensor twice in my '96 Subaru, and not once did it pull a code for it. It always came up with the crank & cam sensor codes - and always in tandem.

    I am not saying it IS the knock sensor, it is just that the electronic timing controls do require constant input about retarding/advancing to meet current conditions and the knock sensor is one of the primary controls of that operation. I think they also depend on the temperature sensors, the mass airflow sensor, and the 02 sensor(s). The 02 sensors, if failing, always pulled codes on my Subaru and the one time I had a problem with the MAS it caused stalling (w/ no code) - not idle issues (in other words, it ran perfectly until it stalled at a stoplight, etc).

    I am not familiar with "dexcool." If the truck does run fine for a while after a reset, then perhaps something is causing the timing to artificially advance. It is apparent to me that the problem does not lie with the cam sensor itself... it is either not receiving a regular signal from the position marker on the cam or it is receiving bogus input from another sensor. Unfortunately OBDII does not always isolate the problem correctly and these electronic machines are really a nightmare to ferret out by traditional means. :mad:
  • dchase1dchase1 Posts: 15
    i think im gonna try the knock sensor zwesx.its 40 bucks.but its cheaper than someone else throwing parts in my truck.from everything i have learned of knock sensors,it seems it is the most likely to go,cause it could have got damaged towing or on a lift.i believe the knock sensor is somewhat fragile.what i want to know is could a bad knock sensor cause the camshaft position sensor to malfunction.at least if it doesnt work i will know its not that rt.sound like a good theory.the other sensors have something to do with timing also,but i do like the knock sensor theory.it seems the most likely.do you think the knock sensor will solve the camshaft position sensor issue.basically the codes say that the camshaft position sensor is malfuntioning and that it is out of range which is 4 - 5 volts.no codes for high or low imput.po340 po340 po341.sinceit says camshaft position sensor circuit,i guess my question is the knock sensor involved in that circut.
  • dchase1dchase1 Posts: 15
    the camshaft sensor is definetly no getting a signal.what besides the knock sensor could cause this.why would it not get a signal from the position marker on the cam.i do not believe my camshaft is bad because it runs like an animal after the idle is relearned till u hit a slight incline or after about 10 miles
  • dchase1dchase1 Posts: 15
    there is also a knock sensor module that can be replaced in the pcm in this vehicle
  • xwesxxwesx Fairbanks, AlaskaPosts: 8,276
    Well, the position marker is typically a contact point or a magnet or something that will activate a signal in the sensor that the position has passed. If it was maybe grimy or the gap was too large, then the consistency of the signal could diminish.... that one was just a shot in the dark though. Because of the strong running right after a reset, I am inclined to think that this is an unlikely scenario.
  • xwesxxwesx Fairbanks, AlaskaPosts: 8,276
    Out of range.... so right, what would cause that? A bad resistor somewhere in the circuitry? I doubt the knock sensor is in the same circuit as the cam sensor, as the info they relay would have to go back to the control unit before to each other. As for the problem being in the control unit.... possible, but impossible to ferret out short of replacing the thing, which is expensive enough that one certainly would not go this route on a whim! :mad: Argh, this whole problem is really frustrating, and it is not even my truck! :blush:
  • dchase1dchase1 Posts: 15
    zwesx hi. it is very frustrating,but i like to figure stuff out.k i'm thinking now that u got me started on the knock sensor that it is intermittent seeing its kind of like a microphone and it is fine at idle thats why no code is set.once it bounces around it malfunctions for a moment or retards the timing whatever and vibrates the camshaft which sets the code for the camshaft position sensor.thats my latest theory.im gonna replace it tommorrow and see what happens. :confuse:
  • dchase1dchase1 Posts: 15
    basically i think that if something vibrates the camshaft that would set the out of range,malfunction code.it could happen when the light goes on after it knocks misfires whatever.now the question is what is it?is the sound i hear on inclines a mislire,knock or a bad universal joint while it upshifts.i think it is the vibration which is causing the camshaft position sensor issue.i believe the sensor and camshaft are good.the sound i hear only on inclines is a faint thud.not sure what it is .doesnt sound like an outright backfire.doesnt sound like constant knocking.one sound one time.dull thud.feels like pulling.tranny is ok.dont thing its universal.doesnt bang real hard.but maybe its slightly bad .dont know.it makes more sense that knock sensor is going or bad.i believe that something is vibrating that camshaft.today it runs like i have a loose electrical connection but i have none.i wondering if a bad plug could cause this.i doubt it.starts fine runs kick [non-permissible content removed] after idle is relearned.tommorrow will tell.STAY TUNED!LOL
  • xwesxxwesx Fairbanks, AlaskaPosts: 8,276
    STAY TUNED!

    Oh, I will! This is a great learning experience, even if it is at your expense. :sick:

    Best of luck to you! Hopefully tomorrow will turn out to be a good day.
  • dchase1dchase1 Posts: 15
    put in knock sensor,flushed and changed coolant.engine runs much stronger,but still runs rough.service engine soon light came on again and gave codes for camshaft position sensor.never did change the plugs,so maybe ill do that next.maybe they got damaged from the old knock sensor.i dont know.it is running much stronger.cuts out a little while driving.the problem is still there but runs alittle better.do u think the spark plugs would affect the camshaft position sensor.starts rt up,idles fine only have problem when it is under load
  • xwesxxwesx Fairbanks, AlaskaPosts: 8,276
    Only if they were firing very poorly. Typically if there is an actual misfire, it will set a code in the system. I would have to read back through to remember what you have done so far, but if it runs good at idle I am not sure how a weak spark could be part of the problem. I have to think that there is something in the camshaft sensor circuit that is to blame for the residual problem, but beyond my previous suggestions I have no idea even where to start. Have you talked about the problems with an independent GM truck mechanic? Perhaps a good one would have experienced a similar problem in the past and could offer some additional advice..... :confuse:

    At least it runs a little better, but it does not sound like the actual problem is found yet. :sick:
  • ajazajaz Posts: 1
    1995 Silverado, 350 engine (5.7 liter), automatic trans, throttle body injection.
    Truck starts, but will not idle or run at any RPM. However, by continuously pumping the gas pedal the engine will keep running up to 3000 RPM. Installed new fuel filter with no change in problem.
    Doesn't appear to be the fuel pump.
    Any suggestions will be much appreciated.
    thanks, AJAZ
This discussion has been closed.