Today on my way to work my sedan started shaking like crazy and lose most power. Check engine light came on and I had to manual shift it to get enough speed to get off the road safely. I smelled something burning and had some smoke coming from the hood near the wipers, I looked under the car and the driver side catalyic converter was fire red. Any advice on how to diagnose the problem? Thanks
2004 g35 sedan 170k

 

First step is to find someone with a code reader and scan the computer and get the code number that caused the check engine light to come on.

 

Would it be safe to drive 10 miles or less? I'm going to get it to a shop tomorrow. The catalyic converter being so hot and the smoke makes me feel like it's not.

 

Also, would OEM G37s Coupe exhaust fit on my 2004 g35?

 

So the mechanics first said they had to replace the ignition coils and plugs in cylinder 4 and 6, they said getting to those coils meant possibly breaking the air intake z tube. Now they are stuck and I believe giving up on fixing it. The VDC light and slip light came on while it was losing power and shaking. Could it be the crankshaft position sensor?
Please help! Thanks!

 

What codes are you throwing? Checked a few threads and they suggest it can be many things.

 

I wasn't in a position to run the codes myself(it broke down near a shop with a good reputation, so I just took it there). They said it only kicked out misfire in cylinders 4 and 6 codes. I guess I'll get the car back and try to test it at auto zone.

 

Got it back from the shop, they couldn't fix it. They replaced ignition coils 4 and 6 and it ran or for about a mile than started running bad and only kicked up a code for cylinder 1 miss fire. Got it home started it ran fine for awhile but started running bad again with no service codes. When I rev it up and the rpms come down I can hear the catalyic converter thuddering and making noise. Could it be the cat that is the problem or maybe the crank and cam shaft sensors? Please help this is my daily driver and I'm lost.

 

take the cats off, they may be melted inside and clogged to ****. you can buy some test pipes or just hammer out the insides of your cats to remove the honeycomb. or just buy new cats, if you have the mulah, but that definitely sounds like a clogged cat

 

If I took the cats off would the engine run rich? Someone at a exhaust shop said it can't be done on newer cars...?

 

Let's not get carried away here and start bashing open cats. The red cat, i would suspect, is the result of running lean from two misfiring cylinders. Cylinder 4 and 6 are on the driver's side of the engine...middle and rear cylinder.

Why are you misfiring? well if the shop changed the COP and plug, we can rule that out.

Next i would check fuel and see if there is an issue with the fuel injectors on those cylinders. I'd do a resistance test on those two and check them against the other 4 injectors. You can then try swapping the injectors to another cylinder and seeing if the codes follow the swapped injectors.

If the injectors check out fine, another possibility is the head gasket popped between the two cylinders. I've seen this on cars with misfires on two cylinders next to each other. Coolant and oil don't mix, but the compression is down. You should do a compression test here to verify.

But like i said, the red cat is most likely a result of running lean on 2 of 3 cylinders on one side of the engine. I'd check fuel injectors and compression

Hopefully your shop suggested this? otherwise they aren't that good of a shop. Pretty standard misfire diagnosis here.

 

Thanks for the reply a everyone. I have a obdii tester on the way from amazon I'll see what codes come up and go from there. I don't have the tools or the knowledge to do all the trouble shooting you suggested. I bought a second vehicle so time is on my side. I'll just take it slow and see if I can get somewhere

 

Put the car one the obdii and it came up code p0300 and the VDC and slip light are on. Idling rough. Ran it around the block and turned it off now the car is trying to turn over but won't start and the battery got weaker and died.

 

p0300 is the random misfire code.

Again, all signs point to a major misfire issue with the car. It's not the cats

I'm suspecting dead or dying fuel injectors here.

 

How much do new injectors cost? Which brand do you recommend? I'm thinking Megan test pipes, new injectors, an spark plugs. Basically a much needed tune up..?