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Electrical Gurus/Brainiacs Needed 700 1986

posted by  Oil Eater on  Wed Aug 28 08:36 CST 2002
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Recently, my 86 740 ti developed a studder. I believe it to be in the fuel injection, as it is a slight drop in idle which is very acute. This causes a little hunting afterward until the next time, within 30 sec or so. then it repeats all over again.

I can't get it to idle at all in gear when this acute drop in idle occours, the engine just stalls.

The engine starts, just fine for abour 20 seconds, then the idle settles out and begins its trouble.

Because it idles fine, this prompted me to unplug the temperature sending unit to the computer. This fixed my woes temperarily. I took it around the block and it didn't stall at stop signs.

When I tried to re-start the warm engine, it didn't want to restart, and smelled rich, until I plugged the temp sensor back in, but now I am back to my studder with what I believe to be the FI.

ANY thoughts, suggestions, know how, past experiences, unrelated stories, tangents are all welcome.

Thanks for "feeling my pain".








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    Electrical Gurus/Brainiacs Needed 700 1986

    posted by  someone claiming to be bagle on  Wed Aug 28 13:21 CST 2002 [RELATED]

    Unplug your oxygen sensor and see if it goes away.

    hth

    bagle 87 745ti








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      Electrical Gurus/Brainiacs Needed 700 1986

      posted by  Oil Eater on  Wed Aug 28 14:35 CST 2002
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      I could only wish it was as simple as spending 120.00 and none of my time, but that isn't the case. I did unplug it, and the symptoms are the same.








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        Electrical Gurus/Brainiacs Needed 700 1986

        posted by  someone claiming to be bagle on  Thu Aug 29 00:28 CST 2002 [RELATED]

        Question: Did you unplug the heater or the sensor part? You must unplug the sensor part, which is a single wire. (please disregard if you've done this)
        Another idea is to check the temp switch on the radiator. On the turbo cars this switch closes at higher temps and turns on the electric fan and advances the timing (timing advance occurs only at idle, as detected by the throttle body switch). The temp switch in my '87 malfunctioned and would close at too low of a temperature. The IAC would not react fast enough to compensate and I got an erratic idle speed. I didn't like the idea of advanced timing @ higher temps anyway, so I disconnected mine at the EXK117 computer. Also, Check the throttle switch.

        Just some ideas, hope they help.

        bagle '87 745t just finished some bodywork








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          Electrical Gurus/Brainiacs Needed 700 1986

          posted by  Oil Eater on  Thu Aug 29 05:41 CST 2002
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          When I did the lambda sensor, I unplugged both the two wire connector and the single wire for good measure. Do you mean that I should have left the two wire connector attached for the test?








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            Electrical Gurus/Brainiacs Needed 700 1986

            posted by  someone claiming to be bagle on  Thu Aug 29 06:29 CST 2002 [RELATED]

            No, that's not neccessary. Two wire plug is for heater in sensor.








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    Electrical Gurus/Brainiacs Needed 700 1986

    posted by  invar on  Wed Aug 28 08:50 CST 2002
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    last visit: Fri Feb 26 21:00 CST 2010
    [RELATED]

    "Because it idles fine, this prompted me to unplug"

    Wait a sec, the problems you're describing are all problems with the idle, what do you mean it idles fine?

    Have you tried cleaning out the TB, replacing vacuum hoses, making sure the TPS is properly adjusted? Perhaps it's your IAC.
    --
    Kenric Tam
    1990 Volvo 740 base sedan (B230F)
    My Volvo 'Project'
    (Page is back up!)








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      Electrical Gurus/Brainiacs Needed 700 1986

      posted by  Oil Eater on  Wed Aug 28 14:17 CST 2002
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      Kenrick,

      I had a good laugh. I had to go back and read what I wrote to see what I meant to say. I should have said that when it is initially started, it idles high, but steady. until the idle settles down to normal rpm that is. since it idles (high, but without skipping) when initially started, that prompted me to remove the temp sensor, which I failed to mention is new. (within last month).

      As far as the TB and IAC go, I have replaced the iac, cleaned the original iac and reinstalled it. this was prior to my idle problem by (maybe) one week. The vac hoses are within 2 months old, and the TB was cleaned and adjusted after the idle problem showed up.

      Sorry for the confusion.








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        Electrical Gurus/Brainiacs Needed 700 1986

        posted by  someone claiming to be David Hunter on  Thu Aug 29 01:48 CST 2002 [RELATED]

        If the problem started after you worked the throttle body and IAC then most likely it is related to something you did. I would review carefully all adjustments. TB switch, base idle with IAC disabled, linkage stop screw. Seem to remember somewhere about possible mix up of plugs the to TPS and IAC???

        Have you checked (resoldered) fuel pump relay and radio supression relay?








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          Electrical Gurus/Brainiacs Needed 700 1986

          posted by  Oil Eater on  Thu Aug 29 05:46 CST 2002
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          Tho problem occoured after I cleaned the IAC, although not right afterward. It was also before I did anything with the TB. I su[ppose it is possible to get the harness plugged into the wrong item (IAC and TPS) I only did one at a time, so I know there is no mix up.

          I have not soldered the fuel pump relay. It doesn't "click" audibly or by feel when the momentary idle drop occours. As for the radio supression relay... I am not sure I even have one. I sure haven't been abel to spot one where it's supposed to be or even in the vicinity.







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