Mark Adams Posted July 23, 2012 Share Posted July 23, 2012 Hi, Freelander 1.8 1998 I just managed to scrape a pass on the MOT due to emissions, despite changing the Cat and O2 sensor the problem is caused by the tester not being able to keep the revs at a constant speed to perform a proper test. When your foot is held at a constant position on the petal it just keeps increasing the revs and will not stay at a constant speed. I have checked the TPS with my osciloscope and it seems fine but I cant see what else would be causing it. It idles fine it only occurs when the car is reved when stationary. Mark. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted July 23, 2012 Share Posted July 23, 2012 Check for vacuum leaks. Quote Link to comment Share on other sites More sharing options...
Mark Adams Posted July 23, 2012 Author Share Posted July 23, 2012 Thank you for the reply, I have also tried that by plugging in my SP ACR4 to check the RPM and tried both spraying carb cleaner and using propane, the RPM stayed static. I tried around inlet manifold and all pipes. I have also performed a vacuum pressure test which gave the correct static reading, indicating no leaks. Mark. Quote Link to comment Share on other sites More sharing options...
marty1a Posted July 23, 2012 Share Posted July 23, 2012 Is the timing ok? Quote Link to comment Share on other sites More sharing options...
Mark Adams Posted July 24, 2012 Author Share Posted July 24, 2012 I have checked that the cams line up and they are perfectly in-line. Mark. Quote Link to comment Share on other sites More sharing options...
Mark Adams Posted September 26, 2012 Author Share Posted September 26, 2012 I changed the TPS (which is what I suspected was the problem) but unfortunatly the problem still exists. Any other ideas? Mark. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted September 26, 2012 Share Posted September 26, 2012 Point your scope / DMM at the lambda sensor signal, also try measuring the coolant and air temperature sensors to check they're in spec, the RAVE manuals pinned in the part numbers forum describe system operation & measurements. Quote Link to comment Share on other sites More sharing options...
Mark Adams Posted September 29, 2012 Author Share Posted September 29, 2012 Hi FridgeFreezer, I have connected my Scope to the Lambda sensor signal and it producing a wave form of the correct frequency and amplitude and also responds quickly to WOT. Using my SP ACR4 to read live data I can see that both the Air temp sensor and CTS and both reading the correct temp (confirmed using a laser thermometer). Thank you Mark. Quote Link to comment Share on other sites More sharing options...
Ally V8 Posted September 30, 2012 Share Posted September 30, 2012 I have had this problem before and was quickly sorted by clamping off the IACV tube during the fast idle test. Quote Link to comment Share on other sites More sharing options...
Mark Adams Posted October 1, 2012 Author Share Posted October 1, 2012 Ally V8, Did you find out the actual cause of the problem? Was it the IACV at fault? Quote Link to comment Share on other sites More sharing options...
Ally V8 Posted October 2, 2012 Share Posted October 2, 2012 I didnt really see it as a problem,it was just a PIA that was stopping me from getting a customers car through the test.We just assumed the IACV was moving and altering the revs,they normally just stay jacked open when the engine is ready,in anticipation of having to control idle speed.The engine was in good condition and running well,no problems reported by the owner or by fault codes in the engine ecu. Why dont you just try clamping the hose off and see if it works - cost is only the fuel you use. Quote Link to comment Share on other sites More sharing options...
Mark Adams Posted October 3, 2012 Author Share Posted October 3, 2012 I will give it a go today but always intertested to know the cause behind a problem. Mark. Quote Link to comment Share on other sites More sharing options...
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