Exhausted: Sounds like an exhaust leak @ cats....

phils89sc

Registered User
My 89 SC has what sounds like an exhaust leak around the cats, but when I reach up around them with the engine running, I feel no leaks. It is the sound that disturbs me. When I first start it in the morning, she sort of sounds like she is "straining". As soon as it starts (cold start), it will fire up then almost "chug" for a couple seconds as it reaches the cold start idle RPM. Then when you listen to it run after that, it sounds like it is struggling very slightly, like it is running out of gas. Also, the exhaust around the cat are is "loud". you can almost hear the cylinders firing. I know it sounds strange, but maybe someone else has had this problem other than me and can point me in the right direction.

After the engine warms up, the "straining" is less apparent, but still slightly there. My idle RPM is fine, about 800 rpm and does not vary and is rock steady. The IAC is new, everything else is factory original except the plugs, which are Autolite Double Platinums w/new Bosch Plug wires (yeah yeah, I know, not Magnecore, could not afford them and the problem was pre-existing anyway) I get no codes either.

While driving, there is another problem that may be related. If I floor it, I get lots of dark gray, or black smoke, and I mean lots. This is not just under full throttle, but at 1/2 to full, mostly at higher rpm's, and I can feel the engine strain, like it is being choked. I have owned 2 other SC's and have never had this problem.

Can someone help me out? I have been told that it may be clogged cats, or partially clogged cats. Seeing how my baby has 228k miles, I don't doubt this, but if anyone has any info at all, I would appreciate it greatly. One more thing, my gas mileage is not what it should be, seems poor.
 
Well...

It sounds as though you may have more than one problem. But from the "choking" description you gave I would say that your CATS may be wide open and your Resonator, if you have the stock one, is probably the culprite...Ace the Resonator if you have not already done so...

The smoke could be a few things, I would start with the Res though...

Brad
 
Smoke ?

What your describing sounds like it could be your Cats but whens the last time you replaced your O2 sensors ? The smoke your seeing sounds like your running your engine too rich. The thunderbird SC was designed to run a little rich on higher throttle to help eliminate knocks and pings but if its thick and black thats no good. Try to see if you can borrow someones O2 sensors and try it out but it may be that your cats are already clogged from the O2 sensors runnin the engine too rich.
As far as the milage that once again points to your O2 sensors.
 
Forgot to mention......Boost....

I know the factory boost gauge also sucks and is somewhat innacurate, however, when I am under full throttle, I am just a hair under 15 psi. From what I understand, and from owning these cars in the past, this is a little too much for a factory setup (around 10-12 psi stock).

Thanks for the help.

Phil
 
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