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"98 Z71 - having lots of problems...

This is a discussion on "98 Z71 - having lots of problems... within the Technical / Maintenance forums, part of the General Discussion category; hi guys.. i could really use some advice here, please.. i've been wanting a full sized chevy truck for a ...

  1. #1
    Registered User Reflection's Avatar
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    "98 Z71 - having lots of problems...


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    hi guys.. i could really use some advice here, please..

    i've been wanting a full sized chevy truck for a long time now. i finally traded for a 98 model k1500 4x4 a few days ago...

    when i test drove it, it cut out when i really stepped on the accelerater and floored it, but other wise it seem to drive fine.. and did so all the way home (75 miles)

    i stopped by auto zone on the way home, and picked up some premium pugs, plug wires, and a fuel filter. after i replaced all that and drove the truck about 30 miles down the hwy it started sort of cutting out and shifting down and back up quickly.. my speedometer was bouncing around badly, and the headlights where dimming and flickering while it was surging and downshifting.
    i had to be very light on the accelerator and drive no faster than 45mph to keep it from doing this.

    i took it to auto zone the next day, and had them run a check with their diagnostics machine which said:
    "camshaft to crankshaft position correlation fault
    the ECM detected that the cam and crank sensor positions were out of time
    probable cause:
    1 - engine mechanical condition: valve timing off
    2 - cam sensor or crank sensor are loose on their mounting"

    the guy gave me a cam sensor and told me that was the problem, so i replaced that and its still doing the same thing.

    when we went to change the plugs and plug wires my dad unknowingly disconnected the positive battery cable first. is it possible that doing this caused a problem with the ECM?


    also.. the alternator is wired directly to the battery. where should it be connected to?

    there's a couple other issues with the truck, but these are my two main concerns right now.

    i would really appreciate any help.. !
    Last edited by Reflection; 08-05-2010 at 12:47 PM. Reason: typos

  2. #2
    FSC Midwest Chapter CountryChevy15's Avatar
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    Re: "98 Z71 - having lots of problems...

    Disconnecting the positive cable first isnt going to do any damage to the ECM.

    What kind of plugs and wires did you put in the truck?

    -2006 Crew Cab Chevrolet 1500-



  3. #3
    Registered User Reflection's Avatar
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    Re: "98 Z71 - having lots of problems...

    Duralast wire set #196158

    ACDelco platinum plugs

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    0_o o_0 0_o o_0 98GreenMachine's Avatar
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    Re: "98 Z71 - having lots of problems...

    The code your describing sounds like the Cam Retard value is off. You will need a scanner that reads the Cam Retard value to determine what its at.

    Also, pull the distributor cap off and see what it looks like underneath. Terminals may be corroded over and arching.
    08 HHR LS - 2.2 | 5 speed | 30 MPG

    98 K1500 Z71 - 204k | L31 | 60E | 3.73's | 3" BL | 33x12.5x15 Dick Cepek F-C II's | Dynomax Ultra Flo X DI/DO | 14 MPG

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    0_o o_0 0_o o_0 98GreenMachine's Avatar
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    Re: "98 Z71 - having lots of problems...

    Specifically what you have is P1345:

    DTC P1345 Crankshaft Position (CKP)- Camshaft Position (CMP) Correlation

    Circuit Description

    This diagnostic trouble code (DTC) monitors the crankshaft position (CKP) and the camshaft position (CMP) signals to determine if they are synchronized. If both signals are not observed by the control module within a narrow time window, the vehicle control module (VCM) will determine that an error has occurred.

    Conditions for Running the DTC

    The engine is running.

    Conditions for Setting the DTC

    When the engine is running, the cam sensor reference pulse is not detected at the correct position relative to the crankshaft position sensor pulse.

    Action Taken When the DTC Sets

    * The control module illuminates the malfunction indicator lamp (MIL) the first time the diagnostic runs and fails.
    * The control module will set the DTC and records the operating conditions at the time the diagnostic fails. The control module stores the failure information in the scan tools Freeze Frame/Failure Records.

    Conditions for Clearing the MIL or DTC

    * The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed.
    * A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22C (40F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70C (158F) during the same ignition cycle.
    * Use a scan tool in order to clear the DTCs.

    Diagnostic Aids

    Check the following items:

    * A loose CMP sensor causing a variance in the sensor signal.
    * Excessive free play in the timing chain and gear assembly.
    * Incorrectly installed distributor - 1 tooth off in either advance or retard positions.
    * A loose distributor rotor on the distributor shaft.
    * A loose or missing distributor hold down bolt.

    An intermittent may be caused by any of the following conditions:

    * A poor connection.
    * Rubbed through wire insulation.
    * A broken wire inside the insulation.

    Thoroughly check any circuitry that is suspected of causing the intermittent complaint.

    Test Description

    The numbers below refer to the step numbers on the table.

    4. This test will determine if this DTC is intermittent.
    5. When the engine speed is raised to 2000 RPM the camshaft retard offset should not vary more than 2 degrees.
    6. If excessive pressure is used when performing this test unintentional damage to the distributor shaft could result.
    7. If the distributor is one tooth off in either the advanced or retard positions the vehicle may run but 0 degrees camshaft retard offset will not be obtained.
    8. If 0 degrees cannot be obtained during this procedure refer to Diagnostic Aids.


    08 HHR LS - 2.2 | 5 speed | 30 MPG

    98 K1500 Z71 - 204k | L31 | 60E | 3.73's | 3" BL | 33x12.5x15 Dick Cepek F-C II's | Dynomax Ultra Flo X DI/DO | 14 MPG

    84 S15 Jimmy 2dr 4x4 - engine/tranny all rebuilt

  6. #6
    Registered User Nova SS's Avatar
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    Re: "98 Z71 - having lots of problems...

    check all the ground cables, straps and battery terminals (and yes only two wires to the alternator, one goes to the positvie side of the battery and the other is a plug into the wiring harness.)
    Automatics are people who cant shift .....
    1998 Chevy 1500 350 / 5 speed
    1965 Nova SS 427 / 4 speed
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    1993 festiva 1300 / 5 speed daily driver.

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    Re: "98 Z71 - having lots of problems...

    ditto Nova SS.

    My alternator went out. Truck did all manner of wierd stuff, just like you described, as alternator died over course of 30-40 miles. Not sure if low voltage condition could cause false codes or not. Perhaps it's more than one problem occuring concurrently.

  8. #8
    Registered User Reflection's Avatar
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    Re: "98 Z71 - having lots of problems...

    Quote Originally Posted by 98GreenMachine View Post
    The code your describing sounds like the Cam Retard value is off. You will need a scanner that reads the Cam Retard value to determine what its at.
    alright thanks. i don't have access to one of these scanners, though...

    Also, pull the distributor cap off and see what it looks like underneath. Terminals may be corroded over and arching.
    i checked, and the terminals aren't corroded at all.



    Diagnostic Aids

    Check the following items:

    * A loose CMP sensor causing a variance in the sensor signal.
    * Excessive free play in the timing chain and gear assembly.
    * Incorrectly installed distributor - 1 tooth off in either advance or retard positions.
    * A loose distributor rotor on the distributor shaft.
    * A loose or missing distributor hold down bolt.

    An intermittent may be caused by any of the following conditions:

    * A poor connection.
    * Rubbed through wire insulation.
    * A broken wire inside the insulation.
    thanks again!
    the new cmp sensor is in there tight, and so was the old one.
    haven't checked the timing chain and gear assembly(not sure about this one)
    i have no idea about the distributer positioning, but the rotor and cap are on tight.




    Quote Originally Posted by Nova SS View Post
    check all the ground cables, straps and battery terminals (and yes only two wires to the alternator, one goes to the positvie side of the battery and the other is a plug into the wiring harness.)
    i've checked and as far as i can tell everything has a good ground connection, but i'm very new to all of this!

    it starts and drives ok 'til i hit about 40-45mph. ..that's when it downshifts and starts shifting in and out of gear, the speedometer starts bouncing around and head and dash lights start dimming.
    Last edited by Reflection; 08-09-2010 at 03:04 PM.

  9. #9
    Astute as fek. DarkCharisma's Avatar
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    Re: "98 Z71 - having lots of problems...

    My old truck was doing something similar, but I had no codes to go off of. Only thing I could think of was the Speed Sensor going bad, or perhaps the ECM was screwed since I had a custom-tuned one in there.


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    Re: "98 Z71 - having lots of problems...

    try taking the distributor cap of and check the screws that hold the rotor button in place if you replaced that when you did the tune up. My truck did the same thing when i had the dealer tune it up, had to have it towed back to them and found that the guy who did the job put the screws for the cap on instead and they are a little longer and caused it to arc throwing the same codes as yours

  11. #11
    Registered User Reflection's Avatar
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    Re: "98 Z71 - having lots of problems...

    Quote Originally Posted by bigbeau View Post
    try taking the distributor cap of and check the screws that hold the rotor button in place if you replaced that when you did the tune up. My truck did the same thing when i had the dealer tune it up, had to have it towed back to them and found that the guy who did the job put the screws for the cap on instead and they are a little longer and caused it to arc throwing the same codes as yours
    thanks for the suggestion. the rotor button is tightened down with the proper size screws. theyre very small.

  12. #12
    Registered User Reflection's Avatar
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    Re: "98 Z71 - having lots of problems...

    anyone else have any idea why it drives and shifts fine until i hit about 40-45 mph?

  13. #13
    Loves GMT400 haters someotherguy's Avatar
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    Re: "98 Z71 - having lots of problems...

    The P1345 code is almost surely because the distributor was removed for intake gasket replacement (extremely common failure on small block Vortecs, practically all of them suffer failure of the factory gaskets) and was not reinstalled properly. It takes a scanner that can read the cam retard, and someone that knows what they're doing, to set it 100% correctly. Without this the PCM can't adjust timing correctly and performance/drivability can suffer.

    P1345 is almost never the cam sensor itself, though they do go bad. On these trucks it's almost always because the distributor has been out and not replaced correctly, base timing not set correctly. These particular Vortecs (big block too) are the only engines Chevy made that requires this unique procedure so people not used to it, even if they're very accomplished mechanics, can make the mistake of not installing the distributor correctly, and not timing it correctly.

    You should also be testing fuel pressure. If it's not around 58psi or better, you probably have a bad pump or failing pressure regulator/injectors, all of which are common issues on these trucks too.

    Richard
    Last edited by someotherguy; 08-10-2010 at 11:32 AM. Reason: clarification

  14. #14
    Registered User Reflection's Avatar
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    Re: "98 Z71 - having lots of problems...

    thanks a ton!

    the only thing is that it ran ok on the hwy all the way back home. it did sputter around a bit and hesitate when i really floored it, but it didnt start doing this until driving the truck about 80-100 miles.

    thats what makes me wonder how it could be an incorrectly installed distributor...
    Last edited by Reflection; 08-10-2010 at 11:28 AM.

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    Loves GMT400 haters someotherguy's Avatar
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    Re: "98 Z71 - having lots of problems...

    Lots of things can be wrong with an engine and be borderline OK until they deteriorate past a certain threshold. As I said you should also be checking fuel pressure. The existence of the P1345 code tells me for certain that you have an issue with your timing. It may have just made it a little bit crappy, based on the degree of how out of time it is...and other contributing factors pushed it over the edge to the symptoms you are experiencing now.

    Have a competent shop set your base timing: this is critical to performance of the engine. Test the fuel pressure. Once these two items are known quantities then proceed with other possible troubleshooting.

    BTW I edited my previous reply because I typed without thinking. I said the small block Vortec was the only engine designed this way, but the big block (and presumably V6 from 96-up but I never messed with them) is the same.

    Richard
    Last edited by someotherguy; 08-10-2010 at 11:39 AM.

  16. #16
    Registered User Reflection's Avatar
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    Re: "98 Z71 - having lots of problems...

    turned out to be a bad speed sensor. located on the transfer case.

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    Registered User Jon4x4's Avatar
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    Re: "98 Z71 - having lots of problems...

    Well atleast you now have new parts lol
    '00 Chevy Silverado Z71, 233k miles
    '97 Ford F250 ECLB, 7.3/ZF5. Tow Pig
    '98 Chevy K1500 ECSB, SAS - Sold
    '94 GMC C1500 RCLB, DD - Sold
    Some guys think that if you got a cooler car that your better then other guys; Those guys are right. - Adam Farrara

  18. #18
    Loves GMT400 haters someotherguy's Avatar
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    Re: "98 Z71 - having lots of problems...

    Still doesn't address your P1345 code.

    Richard

  19. #19
    Registered User Reflection's Avatar
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    Re: "98 Z71 - having lots of problems...

    nope, but the truck runs good. i think it's close enough for now.

    thanks

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    Re: "98 Z71 - having lots of problems...

    hey im having trhe same problem i was just wondering was it a transmission speed sensor ar transfer case sensor my truck is also a 98 chevy Z71

 

 
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