Why is my car not performing like it should!?!?

91BLOWNSC

Registered User
I was wondering if anyone has had any of the same problems, and could give me any input as to why my car sometimes just does not perform as it should. Just tonight I was out doing some "comparative" driving against another friend who also owns an SC. its a 91 Auto just like mine, and his only mods are removed resonator and mufflers. Now I have run him many of times, and beat him, and have run at the track and turn out higher MPH speeds (by like 4 mph); his best is a 15.4. Mines usually around a 15.0. Well tonight we ran them a few times, and he beat me every single time, from a roll, stop; it didnt' matter. I did pull a little the first time on the high end and that was about it. I just recently did a rebuild, but my car seemed to do this before the rebuild also. Sometimes its so fast I can beat everyone, and sometimes I get beat time and time again. We had just raced about 1000 miles after my rebuild, and I came out on top every time we ran them. I don't understand. I have the mods listed below, and he even took my from a start where I usually cream everyone. What are my possibilities. My car does have a rough idle (sounds like its missing) but I don't feel anything when at WOT. I still have the same spark plugs in that were in there when i blew the HG's but they were brand spanking new only a week before, so i didn't think it hurt them at all. Could my car possibly be retarding the timing?? I always use 93 octane because i run the 10% pulley just to be cautious. So I don't see why it would be doing that. It was about 72 degrees out when we raced. Im so confused. This is the first time my car has did this. It seems to change from race to race with someone.
 
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Man...

Come on guys. No one has any ideas? Would would my cars peformance vary so much like that. I need some help to get this thing running right.
 
My car was doing something like that when my cats got plugged. When it was cool it would run strong, after a few hard runs it had no power whats so ever. I am not curtin it was the cats but when I had my cats removed, it never did it again. I did not change anything else. You might want to try that first. Another thing is the knock sensor. Just throwing out a few things. Good Luck

Victor
 
curse said:
My car was doing something like that when my cats got plugged. When it was cool it would run strong, after a few hard runs it had no power whats so ever. I am not curtin it was the cats but when I had my cats removed, it never did it again. I did not change anything else. You might want to try that first. Another thing is the knock sensor. Just throwing out a few things. Good Luck

Victor


Well, thing is I have brand new (well almost) C & L high flow cats on it, so I don't think thats the problem. What about the knock sensor? How do i know if its pulling timing? How could I check?
 
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Anyone? My car seems to run roughly at idle, almost like it has a miss. I don't know if that correlates with the problem or not.
 
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Did you change the O2 sensors when you did the head gaskets? Get those plugs changed as well! You may want to go to plugs one heat range colder and drop the gap down to .045"

Paul
 
your O2 sensors can be bad...And coolant temp switches have been known to go bad after a good overheating and would cause rough idleand a rich condition
 
hmm..

Well it seems to have had simliar symptoms before the HG's blew. Of course the idle wasn't as rough as it is now. So you guys could be right on the 02's I beleive I have bosch and there lifetime warranty, so I will go grab some new ones. My car has never been overheated so I don't think my coolant temp sensor would be bad. I was thinking of changing to my stock pulley to see if that had an performance difference for my engine. What do you guys recommend for plugs. What are the "colder" plugs and where do I get them from? What are the advantages/disadvantages of using them. And why do I want to decrease the gap. Thanks for all the help ahead of time!
 
The car will run a lot hotter with a 10% OD pulley,especially if you dont have exhaust and other flow improving mods including the intake.The coolant temp sensor usually works or it does not it rarely starts to fail slowly.I would change the oxygen sensors and the plugs and change back to your original pulley and see how it feels then.
 
I think Paul pretty much nailed it.

The reason to close down the gap is because of increased (10% OD) pressure to the cylinders.

Lee
 
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