Hi All,

My 1989 240 has just started having idling issues. It starts fine and idles fine for a minute but then slowly starts to hunt and hicup before stalling.

I've checked the following items:

Vac leaks - can't find anyCleaned the idle air control valve (2 pin Bosch model - 0280140516) with brake fluid as per a YT clip. Bench tested it to have 8ohm resistance and also put 12v directly to it and it opens as normal. However when i install it in the car it doesn't open when i start the engine but the wiring harness has 12v going to it. Which is very misleadingI've removed the air flow meter and will spray cleaner on that next

I'm unsure what else to check for or has anybody tips before I start tearing apart everything. Next on my list was to change the rotor in the distribution cap.

Thanks,

Martin

  • After further diagnostic tests on the pins at the back of the ECU for the ECT & O2 Sensor, using test procedures from turbobricks.

    ECT: Passed

    O2 sensor: Failed - it would spike to 3.0v at times and when the voltage went out of range the car started running poor. @carnut222 hooked me up with an O2 sensor and it's back in action again.

    In summary - 2 items had failed here (in tank pump & O2 sensor) & I installed a bunch of other items like leads, cap, etc but lets call this "A little tune up" as I didn't know when these were last replaced

For LH2.4, the throttle position switch adjustment is critical. If the switch is misadjusted, the ECU doesn’t know it’s meant to control the idle speed, so it doesn’t properly actuate the IAC valve. With the engine off, rotate the throttle spool slightly and you should hear a click from the throttle position switch. If not, the switch is likely misadjusted. That’s always my first item to check. If that’s not it, then it could be a number of things...check and report back here.

It clicks when turned ever so slightly.

Is there a test procedure to see if this is working correctly?

Would there also be a test procedure for the MAF?

When the engine is idling so low that its on the verge of cutting out and I disconnect the TPS then it comes back to life but the idle is a bit higher than normal by a couple hundred rpm.

    morch_66479

    When the engine is idling so low that its on the verge of cutting out and I disconnect the TPS then it comes back to life but the idle is a bit higher than normal by a couple hundred rpm.

    Hmm, not sure what the computer sees when you disconnect the throttle sensor - probably goes out of idle control mode so it should put the IAC into a default part open setting. There is a procedure to test the throttle sensor...There are 3 pins IIRC, one should be earthed through the harness, and when the throttle is closed it should provide continuity to the other pin via earth, and at full throttle it should earth the other pin. Basically two normally open microswitches, one closes when throttle is closed, and one closes when throttle is fully open. I suggest checking out the Greenbook manual relevant to the idle adjustment procedure...there’s some info here that may be useful:

    http://www.turbobricks.com/forums/showthread.php?t=321181

    I doubt if it’s the MAF if the car runs fine off idle. Sounds like your base idle may be set a bit too low...try the procedure in the link above and see how you go.

        You say the idle is good for a minute. Is this consistent every time or intermittent?

        What is the idle speed when the idle is satisfactory? How does the engine drive otherwise? Is this problem occuring at hot or cold temperature or both? What happens if your keep the idle speed up slightly? Do you have a video of it stalling?

          carnut222

          https://ozvolvo.org/discussion/comment/191115#Comment_191115

          Hmm, not sure what the computer sees when you disconnect the throttle sensor - probably goes out of idle control mode so it should put the IAC into a default part open setting. There is a procedure to test the throttle sensor...There are 3 pins IIRC, one should be earthed through the harness, and when the throttle is closed it should provide continuity to the other pin via earth, and at full throttle it should earth the other pin. Basically two normally open microswitches, one closes when throttle is closed, and one closes when throttle is fully open. I suggest checking out the Greenbook manual relevant to the idle adjustment procedure...there’s some info here that may be useful:

          http://www.turbobricks.com/forums/showthread.php?t=321181

          I doubt if it’s the MAF if the car runs fine off idle. Sounds like your base idle may be set a bit too low...try the procedure in the link above and see how you go.

          Followed this procedure and all is within spec ?

            ramrod

            You say the idle is good for a minute. Is this consistent every time or intermittent?

            What is the idle speed when the idle is satisfactory? How does the engine drive otherwise? Is this problem occuring at hot or cold temperature or both? What happens if your keep the idle speed up slightly? Do you have a video of it stalling?

            Everytime since this started yesterday afternoon. Temperature doesn't change the effect. To keep it running I need to keep the revs over the ~2,000rpm

            When it idles satisfactory its how it always was which looks to be at 850rpm on the dial.

            Here's a clip of it doing its little dance!

            https://youtu.be/Y3P4JyvnvGI

                morch_66479

                https://ozvolvo.org/discussion/comment/191118#Comment_191118

                Everytime since this started yesterday afternoon. Temperature doesn't change the effect. To keep it running I need to keep the revs over the ~2,000rpm

                When it idles satisfactory its how it always was which looks to be at 850rpm on the dial.

                Here's a clip of it doing its little dance!

                https://youtu.be/Y3P4JyvnvGI

                Wow, that’s pretty strange...not sure what to say???

                  PS I figured out what to say - drop it off at my place and I’ll dismember it and sell the bits LOL!

                  Just gonna check the diagnostic codes now and see what it has to say.

                  I'll get back to you

                  Haha, I'll need to be careful next time I visit. Wouldn't want you sneaking parts off it when I'm not looking ?

                  I have a fuel pressure gauge set-up to use on these...may be worth looking at that. Is the fuel level low, medium or high? Maybe feel the fuel pump fuses and see if they’re getting hot? Just thinking out loud.

                    I followed a YT clip on how to check diagnostics codes and mainly focused on this part where he checked the open and closed positions of the TPS.

                    https://youtu.be/odE9LoTQqwg?t=238

                    For the full throttle circuit i got a code of 3-3-2 when it should be 3-3-3

                    For the idle circuit i got 3-3-2 which tells me its ok in the idle position.

                    Are these accurate codes to go off or am I going down the wrong road?

                    carnut222

                    I have a fuel pressure gauge set-up to use on these...may be worth looking at that. Is the fuel level low, medium or high? Maybe feel the fuel pump fuses and see if they’re getting hot? Just thinking out loud.

                    Like a gauge that goes up on the rail?

                    It's 2/3 full and has the new fuel pump relay installed as i encountered that not starting issue a while back. I'll have a check of the fuses later on.

                        morch_66479

                        https://ozvolvo.org/discussion/comment/191127#Comment_191127

                        Like a gauge that goes up on the rail?

                        It's 2/3 full and has the new fuel pump relay installed as i encountered that not starting issue a while back. I'll have a check of the fuses later on.

                        Yep, I have cut up a spare fuel rail and made it into an adapter with a fuel pressure gauge so it can bolt between the rail and the input hose. The reason I was asking about fuel pump fuses (and maybe also check the relay) is it almost seems to be running out of fuel...I was wondering whether there’s something going on with the pumps and/or electrical supply to the pumps. Advise again, can you drive the car fine if you’re able to keep the revs up? Battery is OK and battery voltage check (not something odd going on with alternator causing voltage spike/drop?)

                          timbo

                          Have you cleaned the throttle body?

                          No i haven't actually, worth a shot?

                            Definitely worth a shot, If there's enough of an oil/carbon film on the throttle body it can cause low idle,and throw the fuel trims off. It's pretty common issue on redblocks and high km whiteblocks.i

                            It will be pretty obvious if that's your issue if you pop the hose off and have a look. If it's particularly dirty it's easier to remove it and give it a good clean but be careful not to split the gasket if you don't have a spare.

                            I did notice oil in the accordion pipe coming from the airbox but not sure if that's been there the entire time. I didn't worry it today.

                            I'm a little lost as to what else i could do with this now, I'm slowly running out of options and i can't find the meaning of the 3-3-2 code during my TPS diagnosis test.

                            I wouldn't worry about that self diagnostic test result at the moment.

                            Does it have any fault codes stored in fuel or ignition ecu?

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