Hello,
I am trying to find a solution to my rpm fluctuations at idle and also to my bad injector corrections.
Concerning the first problem, my rpm needle fluctuates with 50rpms for about 10 seconds when I start the car, and it continues to fluctuate with only ±10 RPMs at idle but I still can feel those fluctuations.
Concerning the second point, the car has all 4 new injectors which were replaced by the previous owner, and for this model of car, the injector corrections should be between 0.75 and 1.25. For a new injector, it should be around 1.
Currently, some of them have 1.20 and some 0.8 but what is important is that they change from one injector to another and I cannot find the reason. I was expecting if one injector is bad, it should remain bad on another diagnosis but in my case
the bad injector shows a good correcting a day after and so on, so I cannot say which injector has problems.
Trying to find a solution to my oscillating idle, while using a Delphi diagnostic tool, I noticed that before the engine is started and also after the engine is shut off, the RPM displayed is 20. Shouldn’t it be 0 in these circumstances?
At idle it shows around 850 (±10) as it should be for this type of car so why it doesn’t show 0 when the engine is off?
I used another diagnostic tool and the same result. Then I tried a diagnosis on an identical car, and there it showed 0 when the engine was off as it should be.
While searching on the internet I found something about the crankshaft position sensor being responsible for the RPM, so I monitored the “crankshaft syn loss counter”.It showed 135 which I assume are 135 times the crankshaft failed to synchronize. I drove the car for a couple of days and it remained at 135.
I am not sure if I am going in the right direction investigating this sensor.
Does anyone tell me what else to investigate?
If this is a Renault as in your heading then you need to tell people what engine you have . Gas or Dielsel . This is mostly a US of A forum and Renaualt has not been sold here for decades. I almost thing you need a Renaualt Forum.
It’s a Renault with a Diesel engine. I posted it here because I couldn’t find a good forum for Renault cars.
All that typing, and nowhere is it mention what kind of vehicle the OP is referring to. 
Tester
I find that hard to believe. There are forums for almost anything you can think of .
When a diesel engine surges, the first thing to suspect is the high pressure fuel regulator.
Tester
OP, explain what injector “correction” means. Is this a ECM parameter that adjusts injection pulse width for non-ideal injectors? i.e. if injector slightly plugged, correction parameter of 1.1 causes pulse width to widen (in time) 10%?
Hello.1 means that the injector is working at full capacity.1.1 for example means that the injector is a bit clogged so the ECU commands 10% more fuel on that injector.0.9 for example means that either the injector is leaking a bit so the ECU cuts off some of the fuel, or it might also mean that it compensates for the other injector that is stuck(so the ECU is sending less fuel on this injector and more on the clogged injector). Usually they should work in pair 1-4,2-3. So if injector 1 has a correction above 1, injector 4 should have a correction below 1 if it can. If it can’t, the other 2 injectors also have to lower their correction to compensate for the clogged injector 1.
Thanks for the explanation. Given this is a diesel engine, common sense says it is pretty likely the injector correction’s deviations from 1.0 are related to the idle rpm variations. Either problematic injectors or problematic injection fluid pressures. I’m just a diy’er, no experience w/your engine, suggest you ask your shop to do the manufacturer’s test of injectors and injection pump. Diesel injection pump problems are more common than diesel injectors by reports here, so might want to start with the injection pump test. You can search for past posts on injection pump problems here if you like, link upper right this page.