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Thread: Spark or fuel cut issue/New to tuning.

  1. #1
    Garrett booster
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    Spark or fuel cut issue/New to tuning.

    New to tuning, although iv messed with it some in the past just different scenarios. Ok so onto the point im getting assumed spark blow out or fuel cut literally just getting into boost i ease into the throttle and as soon as it gets out of vacuum the spark knock power loss light flashes and it bucks. Afrs were around 11.2 or so before it happens, I am running the boost button stage 4 cal for the 87 lm flashing it off ostrich. Iv modified the Wot throttle and part throttle fuel maps according to the Afr charts. I took some timing out of it when starting into boost and also some in the rpm timing table as well to see if it helped the issue but did not, Dist timing is set to 8-10. Had a fwd performance stage 5 cal before that had other issues like a random lean spike and idling issues so i changed to boost buttons cal to fine tune it to my car. The stage 5 cal didn't cutout like this though. "Not bashing anyone's cal by any means" Just saying that its a new issue on a brand new engine. I haven't data logged it yet like i need to im just now getting around to ordering the cable to do so with mpscan.


    Mods are 40% injectors,omnipower 3 bar map, mild pnp work on head and 1mm bigger valves, 52mm throttlebody, npr front mount with 2.75in charge pipe, pnp 2 peice intake manifold, TO4E 54 trim Hybrid with .63a/r exhaust housing and stage 2 wheel, turbos unleashed hybrid header, full 3 in exhaust, forged pistons, fuel system is walbro 255, with accufab adj regulator set to 55psi static. 782 head RN9YCs gapped at 0.30.
    Last edited by cbw1994; 06-25-2018 at 03:57 PM.

  2. #2
    Garrett booster
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    Re: Spark or fuel cut issue/New to tuning.

    Flashed a few more cals to it, and modified them to get a somewhat base to get it too at least quit cutting out when getting into boost. This cal i just redid from BB Stage 4 but rescaled for 58# injectors at 55psi, Retarded timing 2 to 4 degrees in high boost in wot and part map advance, and edited the pump efficiency to a table that i found from another user with very similar Performance mods. Car runs good, idles decent and seems to be pretty good AFRS when starting to get into boost, Around 11.4 or 11.5. This cal is still getting knock indicated from Power loss light, right before it cuts out. I took all the plugs out to compare and none of them appeared to be anything but normal, no signs of detonation or running lean or rich. Any help is much appreciated. Ill post the cal, the only way i can seem to find out to to post them is just sending them to my email and using the DL link to post to it so let me know if it works.

    https://dl-mail.ymail.com/ws/downloa...ZQufgc5_eQwIX-

  3. #3
    turbo addict
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    Re: Spark or fuel cut issue/New to tuning.

    Plug a scanner into the car and have a passenger check how much knock voltage the ECU is seeing.

    I like old school OTC 4000E


  4. #4
    Moderator Turbo Mopar Staff Force Fed Mopar's Avatar
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    Re: Spark or fuel cut issue/New to tuning.

    Did you put a new knock sensor in? Usually spark blowout means too much plug gap or a weak coil. Another guy just had a rash of drivability issues cured by a new coil.
    Rob M.
    '89 Turbo GTC

    2.5 TIII stroker, 568 w/ OBX and 3.77 FD

  5. #5
    Garrett booster
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    Re: Spark or fuel cut issue/New to tuning.

    Haven't put a brand new knock sensor in it yet, i should order one and try it. I got a few coils laying around ill try swapping that tonight, think im also gonna try swapping LM aswell. Its weird it feels like the car hits a wall, but it doesn't break up or have any audible noise i can hear, Knock light comes on and it just cuts out.

  6. #6
    Moderator Turbo Mopar Staff Force Fed Mopar's Avatar
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    Re: Spark or fuel cut issue/New to tuning.

    Old knock sensors are pretty sketchy, had a lot came apart just trying to unplug them so I try not to use old ones anymore. Also, check for any loose brackets and such that could be vibrating against the block or head at a certain rpm and causing false knock sensor readings. IE PS bracket, coolant line bracket, intake brace etc.
    Rob M.
    '89 Turbo GTC

    2.5 TIII stroker, 568 w/ OBX and 3.77 FD

  7. #7
    Garrett booster
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    Re: Spark or fuel cut issue/New to tuning.

    Still having this problem, Little update, i figured since most the electronics at entirely too old i decided to go ahead and change the coil,HEP,Another new Rotor and cap, socketed a newer reman LM, put ar51s gapped a 0.30, and ordered a new knock sensor. Also ordered a GM map sensor to try instead of the omnipower 3 bar that's currently in it. If the map sensor or knock sensor dose not fix it im going to be a complete confusion on what this cars doing. Everything on the car is brand new lol. I logged the car the other day to check knock and its getting knock in cylinder 3 and 4 literately as soon as boost starts to build id say like 3 or 4psi.. Afrs still look good in the 11.3-11.5. before it cuts out of course then i believe it goes lean at the point. Car also has a random miss every now and then which i also don't understand. Oh and on top of that the idle is all over the place upon cold start ups surging going lean and rich which floats the rpms around.

  8. #8
    boostaholic Turbo Mopar Contributor
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    Re: Spark or fuel cut issue/New to tuning.

    Quote Originally Posted by Force Fed Mopar View Post
    Did you put a new knock sensor in? Usually spark blowout means too much plug gap or a weak coil. Another guy just had a rash of drivability issues cured by a new coil.
    That was me...

    Quote Originally Posted by cbw1994 View Post
    Still having this problem, Little update, i figured since most the electronics at entirely too old i decided to go ahead and change the coil,HEP,Another new Rotor and cap, socketed a newer reman LM, put ar51s gapped a 0.30, and ordered a new knock sensor. Also ordered a GM map sensor to try instead of the omnipower 3 bar that's currently in it. If the map sensor or knock sensor dose not fix it im going to be a complete confusion on what this cars doing. Everything on the car is brand new lol. I logged the car the other day to check knock and its getting knock in cylinder 3 and 4 literately as soon as boost starts to build id say like 3 or 4psi.. Afrs still look good in the 11.3-11.5. before it cuts out of course then i believe it goes lean at the point. Car also has a random miss every now and then which i also don't understand. Oh and on top of that the idle is all over the place upon cold start ups surging going lean and rich which floats the rpms around.
    Just a quick question, since you said the knock is in 3 & 4. You did install the intake brace on your two piece correct? I know it seems trivial, but my understanding is that Chrysler put it there for exactly that reason. Vibration was setting off the knock sensor and causing all kinds of issues, and that was their fix.

    The goofy idle almost sounds to me like you have a vacuum leak somewhere. Maybe something that closes up as the engine warms up? Maybe spray some water around the intake at cold startup and see if it changes. Usually I would recommend something flammable, but not right over that exhaust manifold that is getting hot...

    Just don't give up on it. I was at the exact same level of frustration with my combination just weeks ago. Keep digging and asking questions. Eventually you will get it, and have a "DUH!!!" moment. I know I did...

  9. #9
    turbo addict
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    Re: Spark or fuel cut issue/New to tuning.

    How much voltage on the knocks?

  10. #10
    Supporting Member Turbo Mopar Contributor
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    Re: Spark or fuel cut issue/New to tuning.

    if using mpscan, make sure when running an LM ecu and monitoring knock you follow this post also:

    http://www.turbo-mopar.com/forums/sh...=1#post1129028
    89 Voyager LE, 2.5T2 - rest in peace
    87 Charger Shelby T2 (2.4 conversion in process)

  11. #11
    Garrett booster
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    Re: Spark or fuel cut issue/New to tuning.

    like 0.2 to 0.4knock per cylinder on otc scanner, waiting on plug to data log with mpscan. and 83scamp i vacuum leak tested it and couldnt find anything, and on top of that i did the old propane trick and still didnt find anything. Also i do not have the brace on wouldn't clear my coolant lines, and it also has knock is cylinder 2 some as well that i didn't see.

  12. #12
    boostaholic Turbo Mopar Contributor
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    Re: Spark or fuel cut issue/New to tuning.

    Quote Originally Posted by cbw1994 View Post
    like 0.2 to 0.4knock per cylinder on otc scanner, waiting on plug to data log with mpscan. and 83scamp i vacuum leak tested it and couldnt find anything, and on top of that i did the old propane trick and still didnt find anything. Also i do not have the brace on wouldn't clear my coolant lines, and it also has knock is cylinder 2 some as well that i didn't see.

    Without the brace, it could be resonance in the intake. I can't say for sure, but can't rule it out either... At this point I'm assuming you plugged the hole in the bottom of the intake where that brace bolted on. If not, I think you would have way more issues than what you are having. That would have been a HUGE vacuum leak...

  13. #13
    Mitsu booster
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    Re: Spark or fuel cut issue/New to tuning.

    Id sure like to know the outcome of this!!! Mine has the same cold start surge & cut out only about 7-8 seconds of having foot the floor. Rite about the 2-3 up shift.

  14. #14
    turbo addict
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    Re: Spark or fuel cut issue/New to tuning.

    Quote Originally Posted by cbw1994 View Post
    like 0.2 to 0.4knock per cylinder on otc scanner, waiting on plug to data log with mpscan. and 83scamp i vacuum leak tested it and couldnt find anything, and on top of that i did the old propane trick and still didnt find anything. Also i do not have the brace on wouldn't clear my coolant lines, and it also has knock is cylinder 2 some as well that i didn't see.
    .2 V to .4 V?

    I wouldn't even consider them knock. The knock table is 0 - 5 V, .4V is nothing.


    It sounds like there is a vacuum leak to the map sensor. Verify the map sensor is ready the vacuum/boost correctly is where I would start.

  15. #15
    Garrett booster
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    Re: Spark or fuel cut issue/New to tuning.

    Map sensors good. Changed it yesterday and it seems to do alot better not cutting out anymore. Still getting knock, i didn't log it yesterday to see what the voltages was i just know the CE light comes on upon getting into boost. I messed with the cal a little as well pulled a little timing, and i disabled the over boost which shouldn't of mattered but thats what the cutout felt like, so rather the map sensor was bad or something with the overboost settings fixed the cutout. Tryingbe are u saying that the knock table is too sensitive currently and that's why it lights up? Ill post a picture of the knock voltage table. Also whats a bad Knock voltage?


  16. #16
    Garrett booster
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    Re: Spark or fuel cut issue/New to tuning.

    Ran the car some more to try and figure it out,logged it some today and knock voltage was all over the place, I really don't understand this car. I literately got 5volts in 2nd gear at around 4500rpms. 3rd gear pulls were like 0.40 to 0.70 one pull, and the next would be like 2volts. its like it just does whatever it wants, and always throws the knock light as soon as it gets in boost. Plugs show no signs of detonation,look perfect and the air to fuel is great at around 11.2,11.4 at wot throttle. It did have a brand new distributor rotor ---- the bed today though, weird. I'm running out of ideas with this thing lol. Someone chime in and give me some advice please.

  17. #17
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Spark or fuel cut issue/New to tuning.

    Have you tried dumping some race gas in it? Up the octane significantly, and you should see the knock voltage drop to nothing most likely. What is your timing like?

  18. #18
    Garrett booster
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    Re: Spark or fuel cut issue/New to tuning.

    8-10 base. iv pulled a decent amount of timing out of the tune as well. Heres my timing table

    Full Throttle




    Part Throttle


  19. #19
    Garrett booster
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    Re: Spark or fuel cut issue/New to tuning.

    Thought about just changing the cal some for e85 and run it some and see what it does but id like to get it ok on 93 first. Theres no way this thing should be getting knock like it saying it does. Atleast i wouldn't think.

  20. #20
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Spark or fuel cut issue/New to tuning.

    Have you tried the new knock sensor?

    - - - Updated - - -

    ETA: That timing does look pretty tame to me without making any comparisons to my other stuff. Have you tried dragging the brakes to see if you can isolate this more?

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