RPM fluctuations

Slayer92
Fri, 02 Sep 2022 13:09:07 +0000
Maintenance/Repairs

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?

9 posts - 4 participants