Losing Hope

I am the owner of a 2000 Maxima. When the car hit 70,000 miles the service engine light turned on. Shortly after the car would violently vibrate when breaking. When I took in the car for servicing (Firestone Auto in Brighton). After running a full diagnostic I was told one of my cylinders was not igniting properly. I followed their recommendations to replace the coils and spark plugs, did an engine tune up, and replaced the rear breaks. I did not follow their recommendation to replace 3 tires.

I left the shop and a day later when I reached 60mph on the highway the service engine light returned. The breaking problem still existed but now the car would stall as well. I took the car back to the shop and was told that they stood by the initial work but missed the second part of the problem. After thinking it was maybe a vacuum leak they determined it was the motor oxygen sensor that was still preventing the cylinder from igniting properly. The manager was great with customer service, kept me in the loop of what was going on, did not charge me for labor and gave me an assurance that if this did not solve the problem he would reimburse me in full.

When I was called to get the car I was asked if I noticed any exhaust issues and that they recommend I do a full muffler/exhaust replacement for another $734–None of this issues were detected on the original diagnostic just 2 weeks before, nor was there any smoke or smell being omitted from the muffler prior to bringing in the car. I went to pick it up last night and as I turned on the ignition there was a vibration present throughout the car, it continued as i reversed went around the lot and then entered back into the parking space. I went back into the shop and reported the problem. They took a look, asked me to leave the car, and I have yet to hear back.

Any recommendation/suggestions as to what may be causing the problem?

Find another mechanic. They are just replacing parts without finding out what the problem is…or they are purposely trying to screw you.

I don’t understand why you need the exhaust replaced. There is something amiss here. You’ve spent too much money with these crooks.

I think you have several problems and the biggest one is the disconnect between the shop looking at the car and yourself.
JMHO, but no shop should put itself into the position of saying something, having the customer perform the work, and then having to retrace all of the steps.

A engine vibration could be an engine miss, so pull the codes. A brake vibration could be the front brakes and you replaced the rears.
Loose front suspension parts or wheel bearings can also cause brake vibration and even bad tires can do the same.

I won’t even venture any guesses on this vehicle but I know if I were running the shop I would have washed my hands of the vehicle already since diagnosing problems and having the customer do the work always leads to problems.
JMHO anyway.

You interpreted the original post differently then I did. I was under the impression that the shop recommended the work the OP agreed and had everything done except the tires. I don’t think the OP is doing the work but I could be wrong.

OP: Could you clarify for us who performed the work on your car. You or the shop.


The shop has performed all the work.

The “violent vibration when braking” would, at first, seem to be warped brake rotors, or worn steering/suspension. It could, also, be a ruptured brake power booster. If ruptured, when the brakes pedal is pushed, engine vacuum is quickly lost through the rupture. This large vacuum lose would make the engine run very rough as long as the brake pedal is pressed. Let up on the brake pedal, and the engine would run much smoother. // The cylinder misfire could be another problem. Did they change the fuel filter?

You’re right. I misinterpreted the “I followed” part of the statement and apologize for that.

If this brake vibration is in the steering wheel then that would point to the front brakes. If the vibration is in the body and seats that should be the rear brakes.

The engine vibrations sounds like a misfire but without knowing what codes are present it would be difficult to narrow it down.
I’m a bit suspect about the diagnosis of an O2 sensor causing your problem since an O2 is not going to pick on one cyinder. I have no idea why they’re recommending a full exhaust replacement unless they’re working on the assumption that the converter and/or muffler is restricted.
That’s a pretty costly assumption and like the O2 diagnosis will not pick one cylinder either.
Exhaust restrictions are also easily checked with a vacuum gauge.

If they’re absolutely convinced that one cylinder is at fault then a compression test should be done on that cylinder. At 70k miles there should not be a mechanical fault unless the car has been overheated or abused in the past, but that should be step one if a cylinder has a persistent problem. After that, and considering the plug/coil has been changed, then they should look at the injector and its wiring pretty closely.
Hope that helps anyway.