zelle

I have a 3.0L Mazda6S automatic, and had transmission issues in 2006 after I purchased the car. Fortunately it was still under warranty and I had the transmission replaced at no charge.

Recently the CEL came on and the car was having a very delayed response. I took it into the dealership, and their diagnosis found that the air intake boot was split and a throttle position sensor failure. So the throttle body was replaced and they did a fuel induction service. I picked it up on Friday, and they told me to come back Monday so they could put the air hose on (it hadn't come in yet), but it was safe to drive until then.

So it drives okay on the way home, except the transmission bucks twice. Kinda like shift shock, where there is a delayed response getting it into gear and it kicks hard. Then later that night it keeps doing that and the Check Engine Light comes back on! So I figured I would get this taken care of Monday when I take it back in for the air hose. I don't drive it Saturday. Today (Sunday) I tried to leave but it was acting up to where I don't feel comfortable driving it. It wasn't shifting right, it would shift really quick and stay around 2000 RPMs.

What could be the problem now? I already paid them a LOT of money to fix my car, and now I'm having transmission problems suddenly? Could this have anything to do with not having the new air hose on yet? What should I expect when I take it back to them tomorrow? Is it safe to drive there?

Fabrik8

If that car has a MAF, and the boot is split after the MAF, it will cause all kinds of engine problems. Why did they replace the throttle body if the TPS was bad? Why didn't they just replace the TPS? Is that a drive-by-wire engine?

I'd let them replace the rest of the stuff and see how it goes. Anything major will have been diagnosed already. The transmission harshness is caused by whatever is causing the check engine light, because the ECU will tell the transmission will go into a bare-bones limp home mode.

Fixed.

zelle

The throttle body was faulty, there was a TSB out on it from Mazda. I'm not sure about the MAF or if it is drive by wire. I'm not very well versed on car mechanics, which is why I decided to post because I don't want to be taken advantage of.

Fabrik8

Yep, looks like that car is drive-by-wire, so that would explain why they replaced the entire throttle body. It has a MAF too, so if the boot was split after the MAF that should explain the weird engine problems.
Here's some quick technical education to arm yourself with:
The MAF (mass air flow sensor) measures the amount of air (air mass) that enters the intake. If the damaged intake boot is after the MAF, then air that has already been measured will be escaping from the intake, which is likely the problem.
Drive-by-wire engines use a throttle body with an electric motor attached. The motor opens and closes the throttle plate, instead the throttle being actuated by a throttle cable attached to the throttle pedal. Drive-by-wire throttle bodies have the TPS as part of the motor assembly, so it is very integrated and can't usually be replaced by itself. Traditional (cable actuated) throttle bodies have an external bolt-on TPS, so it can be replaced alone. That explains my train of thought.

Good luck, hope everything goes well.

I'm guessing the ECU needs to be reset also; if the engine has had sensor problems for a while than the short- and long-term fuel trims and other parameters will be different with a new (correctly working) sensor. Resetting the ECU will remedy that. Ask them to do that for you, and if they don't (or for whatever reason tell you that isn't important) you can do it yourself really easily.

zelle

Thank you for your help. Do you think it will be safe to drive there?

Fabrik8

It should be fine, yeah.