Results 1 to 10 of 10

Thread: new cam timing woes

  1. #1
    Tuner
    Join Date
    May 2019
    Location
    new england
    Posts
    74

    new cam timing woes

    1989 jeep wrangler swapped a 4.8 nv3500 last year. ran great.
    stock 4.8 was running 24* timing no issues no knock.
    always 93 octane.
    recently put in a summit stage 3 truck cam.
    fueling is close but at wot 4k rpm and above im getting vicious knock.
    base advance is is pretty low(i think) mid to high teens wot
    nothing audible.
    decreased knock vs cyl at 3600 by 10% and from 4k up by 20%
    the tune in post i tried turning down knock sensors but problem still there.
    is this real knock or false?
    harmonics of the new cam? or just straight up to much timing
    Attached Files Attached Files

  2. #2
    Senior Tuner cobaltssoverbooster's Avatar
    Join Date
    Dec 2008
    Location
    Nevada
    Posts
    4,452
    i feel there is too many unanswered questions.
    no wideband? not even an O2 voltage record?
    did you upgrade the springs?
    did you check pushrod length?
    did you do a trunion upgrade?
    did you re-use or replace the lifters?
    did you inspect the oil pump while you were in there? verify sufficient oil pressure? (pump bypass isn't stuck)


    cams shouldn't cause a knock event from harmonics unless they are installed incorrectly (ie: loose hardware, incorrectly adjusted hardware, incorrectly selected hardware [oem springs = no go at this lift])

    did you double check the knock sensor wiring? if you have the early single wire ones then you need to measure the resistance of the sensor from teh harness connection at the back of the manifold. spec is 93-107 Kohm. if its out of spec then do the harness and sensors no matter what. when this happens it sets the knock event off all the time. if the sensor floats in and out of spec then it can turn on and off.
    Last edited by cobaltssoverbooster; 07-06-2020 at 08:38 PM.
    2000 Ford Mustang - Top Sportsman

  3. #3
    Tuner
    Join Date
    May 2019
    Location
    new england
    Posts
    74
    wideband is in the log.
    youre right upstreams are not there. but lt and st are.
    yes ls6 springs
    pushrod lenth just roughed by feel. (roughed by the hundreds of stock ones, my first upgrade cam)
    no trunion
    reuse lifters.
    not loging oil pr but idle is 40 + on stock jeep sender and gauge.
    new knock senors last year when swap was done and everything is grounded like crazy.
    issue only arose after cam swap.

  4. #4
    Senior Tuner cobaltssoverbooster's Avatar
    Join Date
    Dec 2008
    Location
    Nevada
    Posts
    4,452
    i still dont see the wideband. it may be your doing it through the egr but when i scroll the scan it stays at 0 volts. i took a screen shot. did you hid it under a different channel?

    you're right upstreams are not there. but lt and st are. these dont work in power enrichment which is why i asked where the wb was.
    yes ls6 springs. nice. good to ~.550 lift. used them plenty myself.
    pushrod lenth just roughed by feel. (roughed by the hundreds of stock ones, my first upgrade cam) They do sell a set of .010" (.254 mm) and .015" (.381 mm) longer ones for the ls because its common to install small base circles and need just a smidge more pushrod to fix the changes.
    no trunion probably not killing you but keep an eye on the end plates. don't want any needles falling out.
    reuse lifters. listen for sound related to pump up issues.
    not loging oil pr but idle is 40 + on stock jeep sender and gauge. good, probably not a problem. should rise about 10 psi per 1000 rpm roughly.
    new knock senors last year when swap was done and everything is grounded like crazy. hopefully their reputation for failing hasn't become an issue again.
    issue only arose after cam swap.

    are you absolutely sure that there isnt any grounding issues? replace spark plugs? i gap around .032-.035" (.813 - .890 mm)
    Attached Images Attached Images
    2000 Ford Mustang - Top Sportsman

  5. #5
    Tuner
    Join Date
    May 2019
    Location
    new england
    Posts
    74
    wb is using ftp sensor. for some reason the egr was not working.
    ohmed and voltage dropped wire but wouldn't read through egr input.
    that's how i previously tuned it. but now is reading 0 v.
    wideband is grounded to ecm grounds.
    also the rtt isn't working. this was first time trying to use it.
    wondering if i have a bad ecm.
    was mail tuned when swap was done(wont say name but everything was terrible, bought hp tuners and tuned myself. was perfect until cam swap)
    now only issues is rtt will not work and knock 4k and over.
    doesn't sound like a can of marbles haha(dealt with that on a cheap distributor on my 389 pontiac cruise was pinging like crazy but base was less than 0) but also don't want hurt it.

  6. #6
    Senior Tuner cobaltssoverbooster's Avatar
    Join Date
    Dec 2008
    Location
    Nevada
    Posts
    4,452
    have you tried to revert the ecu back to oem form and then copy your existing tune data in to see what happens. im wondering if your fighting a battle with the software due to a possible flash problem.
    2000 Ford Mustang - Top Sportsman

  7. #7
    Tuner
    Join Date
    May 2019
    Location
    new england
    Posts
    74
    ill give that a shot.
    last night i put in vp octane booster and timing set to 15*. booster was supposed to raise 7 points. i run 93. still getting knock.

  8. #8
    Tuner
    Join Date
    May 2019
    Location
    new england
    Posts
    74
    i was dumb. on the rtt and egr issue. both were off in the tune reverted to stock timing table and ve table.
    im starting over but so far still getting knock retard.

  9. #9
    Do you have any knock sensor codes? 24 degrees doesn't sound like alot

  10. #10
    Tuner
    Join Date
    May 2019
    Location
    new england
    Posts
    74
    no codes for knock sensors.
    im only running 15 degrees.
    still having knock retard 4k and above.
    now im having trouble with the commanded fuel, pe is flatlined but randomly when in pe it will command a mid 9 afr.
    these are the file and log where im at now. ive turned off knock sensor in pe and will start reading plugs. but the fueling thing is new.

    im dying on this and am just about ready to bring it to a dyno shop.
    Attached Files Attached Files
    Last edited by shtboxyj; 07-17-2020 at 07:06 AM.