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92 Viper intermittent misfire

Discussion in 'RT/10 and GTS Discussions' started by Steath, Sep 10, 2019.

  1. Steath

    Steath Enthusiast

    Sep 10, 2019
    Has a misfire/no start that comes and goes. Seems to be no rhyme or reason. Appears to have new coils, plugs, wires, TPS, cam sensor, crank sensor, o2 sensors, ASD, and PCM. Acquired this car after someone else worked on it. We had to put the pcm in it to get it started when we 1st got it. We also put in the TPS, wires, plugs, coils, and ASD relay. Cleaned all grounds and load tested the battery. TPS had a open in the sweep so it was replaced for failing. Other parts we did were just preventative/ cheap guess. Previous owner did the other parts we are guessing because they look new. Any known problems we should check? Ignition controller? Known rub through points on the harness? Thanks for any help
  2. 2000ViperRT10

    2000ViperRT10 Enthusiast

    Nov 29, 2004
    I had this problem once. It turned out to be a leaky head gasket.
  3. yehan

    yehan Enthusiast

    Feb 22, 2018
    Hi, fellow 92 owner here. Do you have any codes on the ODB1 reader. There's a way to get this by turning the ignition switch and looking at how many times the check engine light flashes. You can find more in the user manual.
    Check to see when the misfire happens. I once had a misfire in a honda that was due to the coil wire being too loose. There could be many reasons. It's just going to be methodical troubleshooting.
    ViperRed likes this.
  4. InTheZoneAC

    InTheZoneAC Enthusiast

    Jun 24, 2016
    Pull the codes from the scanner. Does it have a harder time starting after driving to temp, parking, then trying to start it again after 5+ minutes of it sitting there? If so as another user said, could be head gasket failure.

    You can also test compression in each cylinder (rent the tool at autozone) or do a full blown leak down test.

    Also another test for head gasket failure, after the car is warmed up a little, probably 5 minutes of idling, and turned off (very important temps arent up to normal and coolant is hot), keep firm pressure on the radiator cap as you remove it with rags over the top. Run a pressure tester on the coolant system and verify you're not rapidly losing pressure. You could easily check coolant levels when cold, but to better see what's happening run a pressure tester and verify you're not losing a small bit a pressure. A slightly warm engine may allow leaks to show quicker than a cold one. Excessive failure could lead to smoke coming out the exhaust, but there's a chance a small leak may not be enough to burn smoke but enough to cause a misfire.
  5. ViperRed

    ViperRed Viper Owner

    Oct 4, 2006
    Yes, as previously mentioned. Pull the codes if you have a scanner, or do it the manual way.

    I had similar issues to you that eventually got worse. It turned out to be a bad MAP sensor. I replaced it and bingo, good as new again.

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