7M Surging and stalling when driving and idle

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  1. #1
    CelicaSupra.com Member
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    7M Surging and stalling when driving and idle

    ok guys im getting really stressed so I was hoping someone here could help... the 7M is in my MK3 1991 Turbo not my MK2 but I thoughts id ask since many here have these in there MK2,

    the car was not starting when I got it but I got it started up, so the guy I bought it from said he stopped driving it because it would stall at lights when idle, and he said it had a misfire in two cylinders his friend told him,,, true I don't know,


    anyway I can drive the car and it does not stall but when you come to a stop it sounds like its going to stall and does sometimes, this also happens when its parked running but no way to guess at when,


    the car idles about 6-700 rpm, here is a video, has any of you guys had this issue?

    https://www.youtube.com/watch?v=ZAlFnnx3yhs

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  3. #2
    Boosting Mod SilverMk2's Avatar
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    Man that thing sounds terrible.... All that janky wiring not helping you. If you loose signal from the CPS or the MAF will shut the engine off

  4. #3
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    Quote Originally Posted by SilverMk2 View Post
    Man that thing sounds terrible.... All that janky wiring not helping you. If you loose signal from the CPS or the MAF will shut the engine off
    I know the guy before was a serious do it yourself guy... I ordered a connector from yodaconnectors.com end of Aug never received it and he wont reply either, I checked the MAF sensor seems ok, checked vacuum lines nothing seems bad and I pulled the Throttle position sensor moves and is clean... im stumped...

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  6. #4
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    Quote Originally Posted by SilverMk2 View Post
    Man that thing sounds terrible.... All that janky wiring not helping you. If you loose signal from the CPS or the MAF will shut the engine off
    What should I be looking for on the CPS?

  7. #5
    CelicaSupra.com Member 4SFED's Avatar
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    What did you do to get it started from not starting at all? What troubleshooting have you done so far? What's the timing set at? Have you checked for vacuum/boost leaks? Which two cylinders are misfiring? Being a wasted-spark ignition like your 7mgte with two cylinders misfiring, one of my first checks would be to see if those two cylinders share the same coil, and if so, that would be a good indication that one of the coils in my coil pack was weak or bad or not grounded well. If you want us to do some long-distance troubleshooting you need to tell us what you've got going on there.
    BTW, the Supra never came with a MAF sensor. It's an AFM.
    Dave Harrison

    current lineup and year acquired:

    '85 white Mark2 7mgte 5sp 1988
    '85 white Mark2 7mgte Auto 2009
    '84 maroon Mark2 6mge 5sp 2013
    '86 red Mark2 7mgte 5sp 2016
    '85 black Mark2 6m Frankenmotor 5sp 2017

  8. #6
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    Quote Originally Posted by 4SFED View Post
    What did you do to get it started from not starting at all? What troubleshooting have you done so far? What's the timing set at? Have you checked for vacuum/boost leaks? Which two cylinders are misfiring? Being a wasted-spark ignition like your 7mgte with two cylinders misfiring, one of my first checks would be to see if those two cylinders share the same coil, and if so, that would be a good indication that one of the coils in my coil pack was weak or bad or not grounded well. If you want us to do some long-distance troubleshooting you need to tell us what you've got going on there.
    BTW, the Supra never came with a MAF sensor. It's an AFM.
    So I changed the main relay and it started, I checked the AFM sorry I called it a MAF, I also checked the vacuum lines nothing seems bad and I pulled the Throttle position sensor moves and is clean, pulled the iac off and even pulled it apart, had a bit of oil residue but clean otherwise.

    I don't know if there is a misfire in two cylinders or just bull but he told me it needed a starter too and didn't lol, the next things I was going to check was CPS anything else you think it might be? Could a head gasket on these cause these symptoms?


    Any help would be appreciated

  9. #7
    Boosting Mod SilverMk2's Avatar
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    Quote Originally Posted by BILLY_GTS View Post
    What should I be looking for on the CPS?
    Broken wires bad connections etc. If you loose the CPS the engine won't run. The wires there take a beating since they are over the exhaust. 7Ms in general suffer from poor wiring connections. They get hot underhood, they're old, and most are beat to $^*@

  10. #8
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    Quote Originally Posted by SilverMk2 View Post
    Broken wires bad connections etc. If you loose the CPS the engine won't run. The wires there take a beating since they are over the exhaust. 7Ms in general suffer from poor wiring connections. They get hot underhood, they're old, and most are beat to $^*@
    I would say looking certain areas wires are like hard and dried up if that makes sense, I can fix wires but some connectors look rough too, any idea of were I can get connectors since it appears yodaconnectors.com scammed me...

  11. #9
    Junior Member r4ntoy's Avatar
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    Check the vacuum switch to the EGR valve if you still have one. It’s located below the intake manifold, follow the vacuum line back from the EGR valve. There is a 12v vacuum relay controlled by the ECU. If the EGU is closed at idle it will mess up the engine vacuum and cause it to stall out. Hope this helps..

  12. #10
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    I rewired a bunch of stuff as there was some shotty wiring and I changed the sparkplugs as they seemed to have some oil on the treads not a lot but appeared still to be fouled, Anyway I got the car to run and not stall and the serge is almost gone, But now there's other problems, the exhaust starts to sputter kind of around 1500-3000 rpm kinda sounds like there is a restriction in the exhaust system I posted a video below, I ran the car for a while at like 3-5K to try and burn the crap off in the exhaust and it did seem to get better as I did it, The car never overheated but once I turned the car off the overflow hose and bottle was overflowing with boiling coolant, I know this can be caused by a bad rad cap but do you guys think my issues can be the common head gasket
    https://www.youtube.com/watch?v=ytLABa8r0pM

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