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Car hard starts, backfires. Retune?

This is a discussion on Car hard starts, backfires. Retune? within the General Help forums, part of the LSx Technical Help Section category; Hey all. First post here after being a lurker for quite some time, didn't think my first post would be ...

  1. #1
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    Car hard starts, backfires. Retune?

    Hey all. First post here after being a lurker for quite some time, didn't think my first post would be one that was asking for help but here it goes. As the title says after a plugs (TR6 .40 gap) and headers install my 98 Camaro hard starts (doesnt crank slow, just continues to crank) and if you don't cycle the key within 2 seconds or so and continue to try and crank it the car backfires hard. Very similar to a gunshot. Sometimes it'll start on the first crank and sometimes it takes a few tries and a few loud backfires before it takes off. After its started the car seems to run fine. Doesn't miss or backfire at idle or any rpm including WOT but it does seem to run a bit rich in comparison to before I put these plugs in. Previous plugs were shot, had a set of TR55s gapped at .50 that the previous owner left in for way too long. Other than the plugs only thing I touched was the tubes going from BBK shorties to TSP 1 7/8. All my O2s are there including the 2 in the y pipe. So I guess my question is is the tune the problem? Can going one heat range colder and a bit tighter plug cause this? It was suggested that I possibly cracked one of the plugs during the install but wouldn't it run noticeably bad during acceleration if that was the case? Any help is appreactiated.

    List of engine mods if that helps
    TSP 1 7/8
    Torquer v2 113lsa with typical top end supporting mods (tuned by Cunningham)
    MTI lid
    Smooth bellow
    BBK 85mm TB
    LS6 intake
    243s
    Last edited by SimpleStocker; 05-05-2016 at 04:12 PM. Reason: Additional information

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    Welcome to the site!

    How's your fuel pressure?

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    Senior Member raynor139's Avatar
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    Has it been tuned since the long tubes. They will cause the car to run rich if it's not tuned.

    Part of it sounds like the fuel pump may be going out. Hence why jeff asked your fuel pressure probably.
    Last edited by raynor139; 05-05-2016 at 06:07 PM.
    Mods - Lid, Skip Shift Eliminator, MGW shifter, UMI SFCs, Founders Lower Control Arms, Founders Panhard Bar, Founders Adj. Torque Arm, UMI Torque arm mount, MWC Drive shaft safety loop, KONI Yellows, Strano Springs, Strano Sway bars, UMI Upper and lower A Arms, 160 thermostat, TSP headers and TSP true duals Monster stage 2 clutch, racetronix fuel pump, Strange S60 rear axle and tune by Frost.

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    Thank you! I don't have a pressure test gauge to attach to the Schrader valve but I can definitely get it tested. It's odd that this just started happening after the plugs. With the wrecked TR55s in there it fired right up no hesitation

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    I'm waiting for my tuner to get back from out of state on family business but it will be tuned shortly. I guess if it's in the tune that'll be dealt with while its strapped down. I just wanted to see if anyone else has had a similar issue while swapping to these plugs but on upon my search I couldn't find too much which was worrying. If it's the pump it's a good excuse to put a racetronix in it.

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    When you installed the ignition wires, did you hear/feel two "clicks" on each coil pack and one "click" at each plug? If not, you may want to run back through each wire to ensure that they are fully seated. Plugs are torqued to 11 lb.ft.? None of the wires are making contact with the header tubes?

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    The plugs are torqued to spec and nothing touching the headers but I don't specifically recall any clicking when reinstalling the packs. They did start to tighten and I guess felt like it "clicked" in but not twice, I'll recheck today. First time changing the plugs on a COP engine

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    Spaz is My Mentor SMWS6TA's Avatar
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    I 2nd checking the plugs and wires.

    How'd the previous plugs looked? oil or gas soaked? burnt?

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    They looked a bit burnt but not fouled. Don't know if this is coincidental or not but it seems the problem is worse during cold start vs when the car is at running temp. During cold start it's almost guaranteed to do it but I've noticed after its warm it starts much easier, there's a good chance it'll start on the first crank vs when it's dead cold.

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    Fuel filter ever been replaced?

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    Have you checked the fuel pressure at the rail yet? I didn't see if you post it.

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    Smiles for 9.5 Years cammed goat's Avatar
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    Car hard starts, backfires. Retune?

    May be an irrelevant suggestion, but also inspect/clean your IAC valve as carbon can gunk it up and cause hard starting or start then stall.


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