I have a 2005 hyundai tucson 2wd v6 that I’ve been having issues with. It has a hard time starting when you turn the ignition key (instead of just turning the key for that second it normally takes to turn the engine on…i have to hold the key in the start position until the engine catches and starts)…replaced the crankshaft sensor but no change. it also starts to hesitate (almost hiccup like) slowing down to turn and or stop, coming to a stop, accelerating from a stop. then it just dies. it turns back on. I’ve cleaned the MAF sensor and the throttle body. I’ve also replaced the throttle position sensor. but I’m still having the same issues. a mechanic thought maybe it’s my catalytic converter but said it’d coat me $2,000 to replace it. is there anything that I can do to fix the issues myself?
$2000 to replace a catalytic converter…your mechanic is insane.You could get an aftermarket cat for your vehicule for $300 and get it installed by a muffler shop for under $100. I think this guy is trying to rip you off. Catalytic converter should last the life of the vehicule…my 99 Corolla has the original cat.
Is the Check Engine light on?
Tester
apparently my check engine light has been burnt out for who knows how long. and Im told that the only error code that shows is for my O2 sensor 
I’ve had this car for about 10 years and I’ve never had to even think about replacing the catalytic converter. but I understand that things do go belly up…but $2,000 for repairs for a 2005 sounds insane to me. I heard something about people using a steel rod and cleaning the exhaust pipes out with it…is that something that people really do and if so…is it possible with my make and model?
get the code read anyways. They are stored regardless whether or not the bulb is burned out. You may want to get that fixed also, you may miss an important error code…
That would be a great way to destroy a perfectly good catalytic converter
The upstream O2 sensor is what controls the air/fuel mixture once the engine warms up.
Replace the upstream O2 sensor if the code indicates that’s where the problem lies.
Also, have the lamp for the Check Engine light in the instrument cluster replaced so you know when there’s a problem with the engine operation.
Tester
Where does nonsense like this come from ? Oh, wait-I forgot if it is on the internet it must be true.
the engine light is definitely on my list to fix. and dang! I’m glad i didn’t listen to the guy and tried the steel rod advice! thank u!
If the mechanic thinks the cat is plugged up, that idea can be tested by temporarily disconnecting or bypassing the cat. Depending on how they do it, it may be very loud, but if the drivability problem goes away at least you know where the problem lies. Ask your shop if it would be a good idea to try that before replacing the cat.
My guess however is that this is a fuel pump problem. A shop fuel pressure test is the way to determine one way or the other. It has to be done when the problem is occurring though to be diagnostic. If the fuel pressure is “iffy”, sometimes shops will attach a fuel pressure gauge in a way so they can see it during a test drive. If the hesitation or stall is preceded by a rapid drop in fuel pressure, the cause of problem has been nearly discovered.
Lets see, the car is throwing a code that indicates a problem in an oxygen sensor circuit. A bad O2 sensor will make the car act exactly like the OP describes. Big mystery!
Seriously, the code should tell you which O2 sensor. Me, I would replace the sensor. It could be in the wiring or computer but it is most likely just a bad sensor. The few times I have had an O2 sensor code, my gas mileage had dropped before the code appeared and replacing the sensor fixed it.
I have never purchased the socket they sell to replace the sensor, since I am not going to put the old on back in I just cut the wire off it and use a deep socket. I use an 18mm spark plug thread chaser to clean the hole and put the new one in with an open end wrench.
hi there! I took ur advice and asked about testing the CAT but the mechanic said it cant be done with my make and model because there’s three pieces to the catalytic converter with my 2005 hyundai tucson not like the “average” models with only 2 Cats. I asked about the fuel filter and pump but was told it’s definitely the CAT. needless to say I’m a bit frustrated.
hi. I went and had the mechanic check for error codes with me thete but no error codes are showing when he checks the diagnostics. no O2 sensor codes no catalytic converter error codes. nothing. is that normal?
I would question the absents of an error code if the cat is bad, but because the problem intermittent is possible… Are you taking the car back to the same mechanic? If yes, perhaps you want to consider taking it somewhere else. Once your mechanic decided on a cause and fix, you may have a hard time convincing him/her to look at other causes.
I go with the suggestion to replace the upstream sensor before dumping money into a new cat. A relatively easy and inexpensive job.
It has been the same mechanic. unfortunately he’s the only one in my small town and I’ve been too nervous to drive it the 30 miles to the nearest well populated town with lots of other mechanics 
I will try the upstream o2 sensor first! i appreciate your help!
The symptoms you describe could definitely be a clogged cat. I presume your shop has done appropriate testing to reach that as the definite conclusion. For the engine to work it has to draw in air and gasoline, burn it, and expel a roughly equivalent amount of exhaust gasses. If the engine is prevented from expelling the exhaust gasses quickly enough, b/c the cat is clogged say, the whole process quickly stalls out. It’s like the old school-boy trick of putting a potato in the teacher’s car’s tailpipe. When the teacher turns the key ready to go home, rrr rrr rrrr , but it won’t start.
Mechanics have various methods to test the cat. Measure its temperature, measure the intake manifold vacuum, compare pre-cat and post-cat o2 sensor readings, remove the pre-cat o2 sensor to partially bypass the cat, etc.
Another reason to not follow that advice, it’s illegal. Big fines if you ever got caught owning a car with a purposely disabled cat installed.
As far as the symptoms, let us know what fixed the problem & how it all turns out. Best of luck.
which upstream o2 sensor do you think I should try to replace first? everything I research says that my 2005 hyundai tucson has 4 o2 sensors. 2 upstream and 2 downstream. with no error codes showing…im not sure which to replace. I’d definitely rather spend $50 on a sensor to see if that’ll help before sinking tons of money into something else.
if it helps any, sometimes the entire city of Tucson has hesitation and stalling issues…
I would go with one at a time. Hang on to the old one and if the code remains after you drive for a while, switch them back and replace the other one.
lol…i’ll have to remember that one!