I finally took a test drive around the block in my 93 T/A. I just got finished installing everything in my sig. Right now it has open headers, Mac-mids. I got the MadZ28 tune yesterday and installed it today, hooked up the O2's and took it for a test drive. Well it runs like crap. Its like its bogging on acceleration but seems to get better at higher RPM's but not gone completely. Like it doesnt have much power. My question is all this because of the open headers?? The O2's are right at the end of the headers so is it messing them up, causing it to run this way? The valves were set only 1/4 past preload and it idles fine just does the above when I drove it. Any thoughts?

 

The O2's might be reading fresh air which should throw a code. I'd say get a exhaust on the and scan for codes. Post up results later

 

Thanks. My Y-pipe is on its way. I'll bolt it up and see how she runs then. The O2's are very close to the end of the headers on these Mac-Mids. Any other thoughts?

 

running open mids like that will make it run like crap. get a Y pipe on there at least and try it again.

 

you don't have much power down low cause you have no back pressure. wait till you get the Y pipe so you can get the down low TQ back all will be fine.

 

Thanks guys. Your exactly right. The power down low felt like it was still stock but the power up higher was a little better. I was like "man I expected more than this!"

 

yup no back pressure. i did that with mine at first.lol bad idea. sounds hoerible and runs like ****

 

I don't agree with that. I ran open headers right after my cam swap. It ran like CRAP!. Everyone said it was because I had open headers and that I would have no torque. Well I had 18" extensions after the o2's so I knew it wasn't my o2's causing it. What I did was pop off my valve covers and readjust my ProMags with the car running. Car ran like a CHAMP after that! I got my y-pipe and exhaust done about 3 days later. NO change whatsoever in the power/performance after it was done. Back pressure is a myth.

To the OP, my money is on your rockers needing to be readjusted, or your o2 sensors reading way off.

 

Hmmm well Im 99% sure it isnt the rockers but it could be. (That 1% chance) These were only set 1/4 turn. I have adjusted many rockers in my time so Im sure it was done right. Im just going to wait on my Y-pipe to get here, try that and if it still runs like crap I will go from there.

 

Did you adjust them with the car on or off?

 

Off topic but I thought when adjusting rocker arms they should be cranked down a half turn not a quarter of preload? I've found that a 1/4 turn was a little loose .

 

Car off. I adjusted them before it was all put back together. I did 1/4 turn to crank it up and then I was going to go back later and do another 1/4 turn, or start over and give one half turn. Suprisingly, there not making any noise but the headers are a little loud to hear them.

 

I have adjusted stock rockers many times myself. I adjust my ProMags for the first time during my cam install, car started and idled great, but fell on it's face when I got on it. I thought it was my open headers, but it turned out to be my rockers not being adjusted properly. I guess my lifters needed to pump back up in order to get an accurate adjustment. I reset the valve lash and preload (I used 1/2 turn) with the engine running, and the car ran great all the way through the powerband.

 

Thanks SS I will keep that in mind if the Y-pipe doesnt cure it. I'll post back with results.

 

don't let the cold get to the exhaust vlvs, bad things will happen

 

A friend of mine had a very similar problem and everyone likes to blame open headers for the problem but after he got his exhaust put back on his car still wasn't running right. After some rocker adjustment and letting the lifter pressure come up it seemed to helpout a lot. Not saying this is your problem but low exhuast back pressure can only rob so much torque. So you may wanna consider some other issues. But I guess we'll see when you post the results. Best of luck!

Kyle

 

The backpressure thing is a myth.

90% chance it's the O2 sensors reading fresh air and telling the computer to dump in fuel. I had this exact thing happen when I drove my car home from the shop with open Hooker LT's. Added a y-pipe and re-set the computer and all problems were solved.

 

o2s are probably reading fresh air. I wouldnt drive it too much either cuz i heard you can burn out your o2s if you drive for too long with no piping behind them ie. open headers

 

Your best bet bro is to just go by a local police station and get their advice

Prob the o2 like most have said.

 

i had 0 issues running open headers