I have been struggelig with the L7X for a while as it have been slightly misfiring on low revs and high torque, and only occaisonally. Not really a problem but still annoying.
First thing was i replaced the coil.
- No improvement.
Then i replaced the spark plugs, since Renault original is expencive and the manual says NGK (also expencive) i went for the Bosch platinum option as it was very accessible at the time.
- No improvement. (old ones on it was NGK)
Then i replaced the HT leads
(very expencive here so it was out of reach when replacing spark plugs at the time, cost from Volvo was over 3000 NOK !!!!! thats roughly 350 euros, from Germany i got them for like 80 euros).
- No improvement.
Then i replaced the cat, it was noisy anyways after 120k - scrambling occaisonally
- No improvement
No fault codes on it at any time other than the lambda warning for unburned fuel (richness regulation). The auto box has no faults either, it have crossed my mind that a problem on the auto box could easily affect the engine performance.
After some searching on various forums, from time to time measuring and searching on the car without results, i found that there seemed to be the BERU UXF79P (ULTRA-X platin) spark plugs to be preferred by some other owners both on price and reliability, its a fairly cheap alternative -so i took a few hours and changed from Bosch to BERU -as a last resort kinda thing...
The car now seems OK and have been so for the last couple of days
(cross fingers)
Anyone with similar experiences ?
Anyone that have a printout of ok and live values when the car is running ?
Only thing that is still bothering me is that the positive readout (diagnostics) of the feed to the autobox computer is around 11v while the ecu says 13.5v. When measuring actual voltage while engine running with multimeter on the auto computer it gets the full 13.5v (diagnostics say 11v at the same time). So it might still be a problem there, either with computer or wiring causing this funny voltage state. Whether or not this has anything to do with the misfiring issue.... well - a "test" autobox computer is not on every corner around here.