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High Idle After TB Cleaning 700 1986

posted by  someone claiming to be Paul on  Sun Nov 12 06:27 CST 2000 [RELATED]

I've already read the FAQ's but still have problem. I decided to remove the throttle body and ICV (idle control valve) yesterday since I was already replacing the engine mounts. I cleaned the Idle valve and throttle body with carb cleaner and blew out with compressed air. The TB did have a lot of build up around the flapper valve and the idle valve was pretty gunky. The only indiaction of a problem was on cold starts when first putting the car in gear. It would usually stall out. Anyway, I cleaned both parts and installed and the idle is now about 1600-1800 RPM. I made sure there is slack in the throttle cable, the throttle rod is adjusted correctly, the throttle stop is correct, and all vacuum lines are on tightly. I don't see anything else to adjust. I did not use a new throttle body gasket after the cleaning. Just tightened it down again. problem maybe? The car runs fine but just idles too high. Note; I did check the positioning of the base idle adjusting screw on the bottom of the throttle and it was turned in all the way to the right. Turning it to the left seemed to increase the idle. I pulled a couple of vacuum hoses off while the engine was running (the small line on top of the TB and the larger line going to air intake boot) but didn't notice any difference. Any ideas?







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    Re: High Idle After TB Cleaning 700 1986

    posted by  someone claiming to be JohnB on  Sun Nov 12 10:24 CST 2000 [RELATED]

    The throttle plate adjusting screw is supposed to be such that the plate is almost closed, or closed just so the plate doesn't stick.

    That means the engine will die, if it isn't getting air from somewhere else, either through a vacuum leak or a stuck aic valve.

    Also, it's not unusual for the idle to have to be readjusted after cleaning a tb that's perhaps been adjusted by a PO.







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      Re: High Idle After TB Cleaning 700 1986

      posted by  someone claiming to be Tim K. on  Sun Nov 12 10:34 CST 2000 [RELATED]

      I understand that there are a couple different adjustments that can be made on the fuel system such as at the AMM and at the TB. Is this what you're refering to when you mentioned the adjustments done by POs? Aren't these adjustments attempts to "fix" a problem that they don't want to have done correctly (ie: fix the real cause)?







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        Re: High Idle After TB Cleaning 700 1986

        posted by  someone claiming to be Zee on  Mon Nov 13 18:41 CST 2000 [RELATED]

        Frequently the PO will fool with the throtttle cable, the linkage at the front of the TB, and the thumb screw to get the idle to compensate for a dirty TB.







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    Re: High Idle After TB Cleaning 700 1986

    posted by  someone claiming to be Steve Ringlee on  Sun Nov 12 06:33 CST 2000 [RELATED]

    Did you move the throttle position switch in the process? This tells the ECU the position of the butterfly. Check it using the FAQ "click" test.

    Also, it is easy when removing everything to tear a vacuum hose or air intake hose. Look closely at both, especially the air intake.

    Finally, clean out the electrical connections to both the TPS and IAC valve with electrical contact cleaner (such as DeOxIt from Caig Labs), grease with silicone dielectric and reinstall. Removing them may have broken an otherwise-corroded connection.







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      Re: High Idle After TB Cleaning 700 1986

      posted by  someone claiming to be Paul on  Sun Nov 12 09:50 CST 2000 [RELATED]

      I didn't move the TPS at all when removing the TB. I just disconnected it from the wiring harness. All hoses are fine. I had just replaced the engine wiring harness with a new one a few weeks back and it ran fine. I'm sure there's no problem with the connectors since they're new. I did the spray test for vacuum leaks with carb cleaner but didn't find anything. At this point I'm leaning towards replacing TB gasket with a new one and perhaps the O-ring seal within the adjustment screw.







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        Re: High Idle After TB Cleaning 700 1986

        posted by  someone claiming to be Elliott Freis on  Mon Nov 13 08:31 CST 2000 [RELATED]

        Did you spray-clean the TB with the TPS in place? If so, you may have killed the switch contacts with the fluid. Did it myself.. luckily I had a spare. Easy to check if you have a tester, the information on how to check it is in the FAQ.

        -Elliott







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          Re: High Idle After TB Cleaning 700 1986

          posted by  someone claiming to be Paul on  Mon Nov 13 12:58 CST 2000 [RELATED]

          Yes I did clean the TB while the TPS was still attached. I made sure I didn't get the outside of the TPS wet though. Unless it has a way of getting to the inside of the switch from inside the throttle body, I wouldn't think I screwed it up. It does "click" like it's supposed to however I will doublecheck it tomorrow. I purchased another Idle Control Valve today and should have it tomorrow also. The local Volvo specialty shop seemed to think it was at fault. I've cleaned the ICV's before on my two BMW's and have never had a problem with them. They're both made by Bosch.







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            Re: High Idle After TB Cleaning 700 1986

            posted by  someone claiming to be Elliott Freis on  Tue Nov 14 09:38 CST 2000 [RELATED]

            I believe it can still leak down the spindle and into the case, however I would say it is an unlikly thing. Mine did die due to carb cleaner, but it got some spilled in it off of the TB. It did still click, however.

            good luck!

            -Elliott







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              Re: High Idle After TB Cleaning 700 1986

              posted by  someone claiming to be Paul on  Wed Nov 15 12:32 CST 2000 [RELATED]

              Ok, the latest. Still have 1600rpm idle. I've removed the the TB three times and can't find anything wrong with it. I installed a new TB gasket. TPS seems ok but I used electrical contact cleaner on it anyway and blew it out with compressed air. I swapped the idle control valve with a known good unit and nothing changed. All idle valve hoses are in good shape. No obvious vacuum leaks, although I think it seems to have one. Running out of things to try. I disconnected the idle valve while engine running and it maintained fast idle. I disconnected the TPS with engine running and the idle started to increase. Going to check the temp sensor for the ECM next. Maybe I knocked something down there. What a pain!







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                Re: High Idle After TB Cleaning.....Update 700 1986

                posted by  someone claiming to be Paul on  Mon Nov 20 12:37 CST 2000 [RELATED]

                Fixed the darn thing today. I went to the local wrecking yard this weekend and pulled the throttle body and TPS off a 84 240 ($40) and installed it on my 740 after giving the TB a thorough cleaning. Once everything was bolted up it idled where it had before all this started. I really think the main problem was the TPS since I couldn't see anything wrong with the old TB. Somehow I must have fouled the old TPS when I cleaned the original TB. What a relief!







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                Re: High Idle After TB Cleaning 700 1986

                posted by  someone claiming to be AL on  Thu Nov 16 15:39 CST 2000 [RELATED]

                I had the same thing happen last summer. The tech didn't remove the TB to clean it, he just disconected the inlet pipe and used carb cleaner and a brush. Well a far I can figure is, the garbage taken off the TB dripped into the idle control valve underneath. It took about 2-3 weekes for it to clear out. So I had to put up with the 1100-1200 rpm. At my old dealer they removed the TB and cleaned it on their bench and in the parts cleaner. From now on I'm going to do it myself.







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                Re: High Idle After TB Cleaning 700 1986

                posted by  someone claiming to be Paul on  Thu Nov 16 13:14 CST 2000 [RELATED]

                The saga continues with this idle problem. Does anyone know if the idle control valve is activated (vibrates) when the ignition is put in the start mode (all idiot lights on but not cranking)? I've got a 3 series BMW which uses the same idle control valve and I plugged the Volvo valve into it and it activates when the ignition is in the start position. Both cars use Motronics so I can't imagine why the would be a difference.






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