OK. Yet another problem with my car. For awhile now my car has had considerably less power than it used to. It's not as quick as it used to be and I've actually had a time where i couldn't even do a burnout. The car seems to be cutting out a little, however it's done that ever since i bought it. I also checked the vacuum pressure to see if i had a bad cat but it held a steady 19 PSI even after idling for 15 minutes. now I also checked my catalytic converter inlet and outlet temperatures and was baffled by what i found. The inlet temp. was about 240* however the outlet temp. was about 125*. Now the outlet temperature should be at least 100* hotter that the inlet temperature. so I'm not sure what's going on. should I just replace the car or should I check into other things first. I first noticed this after i replaced my fuel pump, but i didn't drive the car for a month so it was kind of hard to tell if it were different. any and all help is much appreciated.

 

How many miles are on the motor??

 

Why do you think your exhaust gases would be hotter after the catalytic convertor? That's a new one on me.
But you're right, a plugged convertor would rob you of power.

What on earth is your "vacuum pressure"? That's an oxymoron right there What's 19psi? Your vacuum at idle is 19"hg? Or fuel pressure, or...?

I'd do the fuel filter first, if it hasn't been done in a while. That's what I see most often as a mystery power robber.

 

lol, my bad, meant to say HG. The engine has about 137K miles, but do you really think that I could lose that much hp in that amount of time, I would have thought it would be gradual.

everywhere I have read says that the catalytic converter outlet temp should be about 100* hotter than the inlet temp.

here's once source:
http://autos.yahoo.com/maintain/repa...ques083_0.html
(middle of 6th paragraph)

The fuel filter shouldn't be the problem, considering that I replaced it when I replaced my fuel pump (December '06)


I've yet to test my cylinder pressure, it's going to be a PITA, but I should do that soon to see if maybe I have a burned valve or blown a head gasket.

I'll also check my O2 sensors tomorrow, maybe they're going out.

Is there anything else i can test? Any thoughts on what the problem may be?

 

I've never heard that before. I'm pretty sure cats didn't re-burn the hydrocarbons, just forced them to plate onto the platinum and form different molecules, CO2 rather than CO for example. I didn't think that was exothermic. But hey, i've never checked.

Does your check engine light stay on when you're driving? If it doesn't (but it does flick on when you first start it, indicating the bulb is fine), then it's not your O2 sensor.

Did you try the vacuum test they mentioned in that article? Like make sure you have more vacuum at 2500RPM sitting in the driveway than you do at idle? That's a good method. If that doesn't show higher vacuum at higher RPM like that, then you most likely need to change out the cat.

I kinda doubt it's something internal and serious, like a broken ring or anything. I'd leave the pressure and leakdown tests for now.

 

OK, well I just removed the cat and apparently the previous owner gutted it. Car still performs the same so now I just have a slow loud car. but I did unplug the O2 sensor on the exhaust manifold and nothing happened. I then hooked my car up to a scanner and found no codes but it showed that the O2 sensor wasn't getting any reading. However it would flicker on occasionally so maybe theres a bad wire. The ECU was saying that the engine is running lean but I don't know if I should trust that right now with the O2 sensor all messed up and my exhaust smelled very rich. A buddy of mine is getting an '89 V6 Trans Am parts car, so I'll just pull the O2 sensor from that. Does anybody know what the MAF should be reading? I have about 9-10 g/s. maybe I'll just give it more of a tune up: new wires, distributer cap/rotor.

I also forgot to mention that my engine sounds like it is cutting out. I've heard of it happening before but I don't know what causes it. Also if i rev the engine to say 4500 RPM and let off i get backfire. Maybe just because I'm running rich? I'm going to put the cat back on tomorrow so I don't burn a valve, but i don't really know what else to check now.

 

Alright, so I figured that I should do a follow up post. After countless hours of testing, cleaning, and replacing parts I've finally found what my problem was. Turn out it was the fuel injector connector to cylinder #5. I'm going to get a new injector harness or just the connector and splice it in.

http://www.cascadecrew.org/phpBB2/viewtopic.php?t=3346