des90 Posted July 4, 2011 Share Posted July 4, 2011 Running great then starts doing this- Gun the engine pulling 4 to 5000 rpm thro the gears and when the throttle is released the idle seatles at 1200 rpm-swicth off and start again and back to normal idle 760rpm.If its left idling at 1200 for a couple of minutes it suddenly drops to 900rpm and then stays there.If i just drive about not using more than 3000rpm all stays as normal-Anybody got any ideas where to start? Quote Link to comment Share on other sites More sharing options...
Richard Spandit Posted July 4, 2011 Share Posted July 4, 2011 Running great then starts doing this- Gun the engine pulling 4 to 5000 rpm thro the gears and when the throttle is released the idle seatles at 1200 rpm-swicth off and start again and back to normal idle 760rpm.If its left idling at 1200 for a couple of minutes it suddenly drops to 900rpm and then stays there.If i just drive about not using more than 3000rpm all stays as normal-Anybody got any ideas where to start? Check your throttle linkages/cables are free - could be a slack return spring. Can you hook the pedal up with your foot the next time it idles high to see if that makes a difference? Quote Link to comment Share on other sites More sharing options...
zoltan Posted July 4, 2011 Share Posted July 4, 2011 Are you running an idle air valve? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted July 4, 2011 Share Posted July 4, 2011 Are you running an idle air valve? If you are, this is the prime culprit - a dodgy/sticky one of these... Quote Link to comment Share on other sites More sharing options...
des90 Posted July 4, 2011 Author Share Posted July 4, 2011 No prob with acc cable etc-when its running at 1200 rpm the quadrant is on its stop.I am running a rv8 idle valve and have tested it several times all seems ok-and why would it only do it when the engine is driven hard? Quote Link to comment Share on other sites More sharing options...
zardos Posted July 4, 2011 Share Posted July 4, 2011 Running great then starts doing this- Gun the engine pulling 4 to 5000 rpm thro the gears and when the throttle is released the idle seatles at 1200 rpm-swicth off and start again and back to normal idle 760rpm.If its left idling at 1200 for a couple of minutes it suddenly drops to 900rpm and then stays there.If i just drive about not using more than 3000rpm all stays as normal-Anybody got any ideas where to start? A little more info would go a long way to help you. Are you running MegaJolt, MegaSquirt 1 or MS 2 ? What version and what mods, etc? What Engine type 3.9, serp or non serp, 4.0, 4.2 ,... ? I assume you are running MS2 to run the standard RV stepper motor idle valve or possibly using an external circuit to convert it from the PWM valve that MS1 can drive? Quote Link to comment Share on other sites More sharing options...
des90 Posted July 4, 2011 Author Share Posted July 4, 2011 5.0 LTR-4.6 injection-edis 8 ignition-ms2- 4.0ltr serpentine front end Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted July 4, 2011 Share Posted July 4, 2011 Take a look at your idle valve % in megatune, see if that is holding it open at all when it shouldn't be, that way you know if it's a software problem or a hardware problem. Also try unplugging the idle valve and try again, see if it falls properly after a ranting then. You could also have a worn spindle in the throttle body if it has come off a high-miler. Quote Link to comment Share on other sites More sharing options...
des90 Posted July 4, 2011 Author Share Posted July 4, 2011 Yes in megatune all looks ok-unplugging the idle valve is a good idea-i'll try that-if its ok that would mean duff idle valve? Take a look at your idle valve % in megatune, see if that is holding it open at all when it shouldn't be, that way you know if it's a software problem or a hardware problem. Also try unplugging the idle valve and try again, see if it falls properly after a ranting then. You could also have a worn spindle in the throttle body if it has come off a high-miler. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted July 4, 2011 Share Posted July 4, 2011 Yes in megatune all looks ok-unplugging the idle valve is a good idea-i'll try that-if its ok that would mean duff idle valve? Well, duff or dirty The Bosch 2-wire ones are pretty reliable, especially if you get a plastic one, but I can see why you want to keep using the Rover item. Quote Link to comment Share on other sites More sharing options...
des90 Posted July 4, 2011 Author Share Posted July 4, 2011 I want to stick with the rv8 type as i believe they are the most reliable and all the wiring and set up is done now- the doner vehicle had only done about 50k so that would suprise me if it was duff Well, duff or dirty The Bosch 2-wire ones are pretty reliable, especially if you get a plastic one, but I can see why you want to keep using the Rover item. Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted July 4, 2011 Share Posted July 4, 2011 Post up pics / screen dumps of your PWM valve and closed loop settings, amd assocaited settings - these if wrong or even off a tad can cause havoc. Nige Quote Link to comment Share on other sites More sharing options...
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