Hey guys,
I drive a late-2009 Daihatsu Cuore CX CNG. I've driven it about 28000 KM, with roughly only 5000 KM done on CNG. I drive purely on petrol. I have been taking my car for service and maintenance to the authorized Toyota & Daihatsu dealership from where I bought the car. I want to discuss a particular engine tuning/performance issue that has been bothering me since ever.
When I drive on petrol at say a fixed speed (let's say 40KM/H), often I feel as though while driving the engine periodically is being pulled back. There are no perceivable jerks to the actual car (as when the tuning is completely out). But the drive isn't smooth, and you can feel the engine isn't running smoothly, and rather grinding somehow. You know how a car is supposed to run smooth on the road, but it doesn't, and instead, you feel that the car is labouring on the road, grinding down. The confusing bit is that this doesn't happen all the time. Sometimes the car runs smoothly at a fixed speed. If I step on the gas and boost the car, it is alright. But that's not really practical in the city, where I really like to drive at a moderate but fixed speed in peace.
I really can't describe it any better. Which is why none of the test drivers/mechanics at Toyota seem to ever understand it. Has anyone of you ever felt it?
At 25000 KM, I should add, I replaced the stock tyres with new Dunlop DigiTyre Eco. I've experimented with different tyre pressure (28psi appears to be the best), so I suppose we can safely rule out the drive not being smooth due to tyres.
Also, recently, after driving in the rain, with inches deep water piling up on the roads, I took the car in for a service as well as engine tuning. But the drive became uncomfortable after that. I took the car in again the next day, and Toyota mechanics took about 15 minutes to do a quick fix. It was better, but the drive again wasn't comfortable, especially in lower gears, such as second and third.
Pissed, I took the car to another auto shop, a very old one my dad has been taking his cars for decades. However, I had to take the car in there two more times subsequently, to get the car running just the way I wanted -- that is, running smoothing in lower gears, even with the airco running.
However, after 1.5 weeks of running smoothly, the drive has become uncomfortable again. I don't understand why this could happen. I took the car again to that auto-shop, and they only looked from the outside and said the tuning was fine, but if I felt something was wrong, I'd have to leave the car. I didn't have time, so I didn't. But I was wondering: what could be the case here? Why is the car losing its tuning settings (or anything else) after a week or two?
Any help in this regard will be very much appreciated. Thank you.
Cheers,
Ayaz