$550 oil change/air filter and worried about future problems

I recently brought my 2007 mazdaspeed3 into the local family-owned shop for a routine oil change. I purchased an air filter at their suggestion while it was being serviced. 300 miles later my car began losing power upon acceleration. Upon inspection I found that they had installed the wrong air filter (too small) creating a 2" gap in the air box allowing unfiltered air to flow freely into the turbo/intercooler/engine. I took it to the dealership and they diagnosed a bad MAF sensor, installed the correct air filter, and did an “emmissions service” to clean out the system. My question is: What is the likelihood that damage was limited to the sensor and if I collect payment from the shop at fault for the work already done, does that preclude me from additional damages if future problems surface as a result of the improper air filter installation?

If it messed up your MAF, then your engine was surely injesting debris it was not intended to suck in. Sand is particularly tough on cylinder walls but it’s hard to injest with all the twists and turns in the intake path. Any damage will be tough to identify in the short term.

Most businesses that pay claims will have you sign a waiver to protect them from future claims.

Yes, you want to make sure the intakes were cleaned out, but I would think the dealer did that when they discovered the too-small air filter. If it runs well now, you’re probably fine. If you want to make double-sure, have a compression test done on all cylinders. If they’re up to spec, don’t worry be happy.

If it’s running fine now you should be okay. My guess is that you have a “hot wire” type mass airflow (MAF) sensor and the free flowing cool air simply caused it to overstress and burn out. A hot wire MAF actually measures the amount of airflow by how much current is required to keep the wire hot. Well actually, the wire’s resistance changes as it cools and affects the current draw, but…oh, nevermind.

300 miles is really almost nothing unless it were a really, really, really severe environment.

Sleep well.

Nice car!

I agree that there’s probably no permanent damage, but I hope you will reconsider where you take the car for service from now on.

I’m not a fan of dealer service departments, and I’m not suggesting there’s anything wrong with family-owned shops (I patronize them myself), but anyone who can’t install the correct air filter in a car is not to be trusted. Even a non-mechanic should have noticed a 2" gap. Something is seriously wrong here.

What does the family-owned shop have to say about this?

Thanks for the info. I really don’t know how the shop could have made the mistake. It was my first time there but they seem like a very well-heeled shop and I don’t see how they could get that way without satisfied regular customers. At first they were very defensive, but once I showed them pics of the gap in the air box they were cooperative. THey even dropped off the correct filter on my doorstep the night before I brought the car to the dealership(I wound up towing it so the filter wasn’t needed). They also said that when I get it all taken care of they will reimburse me for out-of pocket expenses.

The car runs fine now. The miles were on a highway… 3 days to work and back. The final day I drove through some pretty torrential squalls on the way home and I’m now wondering if the open intake could have allowed a drop of water to hit the MAF, which may have screwed it up.

That’s actually a plausible theory. That could have thermal-shocked the element.

Unlikely, but plausible.

The MAF is the cheap part. I would more worry on any bit of debris entering the stream of your turbo spinning at ~200,000 rpm and damaging it. However a damaged turbo by debris simply gets noisy and oil consumption goes up.

I know everyone here thinks I’m a dumb gun totin Republican hillbilly.

I can understand how somebody would put the wrong size air filter on a 1974 Oldsmobile with a 4 bbl carb on top, but these days with the contraptions they have for air filter boxes, how in the hell do you get the lid to shut on the wrong size air filter?


Its easy as long as the filter is too small

I assume it’s one of those rectangular filters that fits in a box, I would think they would have noticed a 2" gap at the end if they were paying attention to what they were doing.

The filter is rectangular. The one they put in was the right width, but too short. When pushed to the front of the box, everything looked ok, but it left a gap in the back. If pushed to the back, the gap was in the front. I agree that it’s pretty incredible that they used the wrong part.