I have used Auto-RX in the engine of 160,000miles Volvo. I did the cleaning cycle and now I'm at the end of the rinsing cycle. Before ARX the engine was perfectly fine, basically I used ARX as preventive maintenance. However since the beginning of the cleaning phase, the engine developped hesitations when it is cold. It only happens during the warmup period. Once at operating temp the engine is perfectly fine.
These hesitations really started to happen right after I started ARX and are still present now that I'm at the end of the rinsing phase. Personally I haven't seen any benefit with ARX, I'm not saying that it doesn't work but just that my engine probably didn't need it since it was rather clean before. However I'm a bit concerned about these hesitations. Again this may not be due to ARX but it's strange that it started exactly when I started the cleaning phase (which was started with the same oil that was in the engine before). It would be a weird coincidence if it's not ARX. The oil filters have always been changed. I recently changed the fuel filter and air filter, spark plugs, cleaned TB and the O2 sensor has been changed last year but I still get those hesitation, only happening when engine is cold. I have followed application instruction properly.
Some people told me this could be due to a sticky valve...but isn't ARX supposed to cure that or at least not cause that? Do you think that ARX can cause this? What should I do: stop using ARX or pour in some more?
I would think its unrelated. It takes at least 200 miles before ARX starts to clean anything up. A hesitation is normally due to fuel or spark. Might want to try a fuel system cleaner, or look into plug wires or timing. Could be fuel air mixture is either too lean or overly rich when the motor is cold. Do you have a computer controling the fuel air mix? Might want to disconnect the battery for a minute or two, then let the computer reset itself.
Thanks for your replies. I have cleaned and renewed most parts of the PCV system short before starting the ARX treatment. As for the 200 miles since ARX get active it's possible the hesitations started after that. 200 miles is about 3 days for me, I don't really remembered exactly when it started but it was fairly short after starting ARX.
The engine fuel/air ration is ECU controlled and I have reset it several times with no luck. Plugs are new, only the HT wires are stock but I assume they would cause problem when engine is warm as well.
Is it possible that ARX has desludged the ring pack but the rings cannot get full elasticity until they are warm, causing some hesitation?
