Just got back from the track today and I am dissapointed. Last year I was able to get my 95, auto, 2.73 Z28 to go 13.7's @ 101 all day long with nothing but loudmouth. Now after Ive added pacesetter longtubes, no cats, cold air, and even a trickflow elbow, the best I could get is 13.89 @ 100. Something definatly isnt right. The car was dead hooking and getting the same 2.0 - 2.1 60' I got last year, so its definatly down on power. I always thought after I added longtubes the car lost its bottom end torque big time but now I have proof. Does anyone have any ideas what could be going on?

 

Sounds like a miss somewhere. arcing plug wire, switched wires, bad spark, bad coil. Something ignition related.

 

i burned a wire so gradually it took me a while to notice it. It wasnt until i lost to a stock mustang that i knew something was supremely wrong, the first thing i noticed was a lack of bottom end grunt.

I hope somebody can provide more of a differential.

electrical: wires, plugs (probably new), opti (cant really test for this)

fuel delivery: pump (unlikely), filter, injectors (dirty)

I'd check electrical first.

 

Plugs and wires are new and been checked, checked, checked again, and rechecked after that. Seriously I've done it 5 times and had a friend help to make sure I was right. The Opti has about 5000 miles on it. The coil I havent done anything with. Anyone know how to check a coil? As far as fueling goes the car has a 255 walbro that has about 5000 miles on it also. I have also checked fuel pressure and I have a good 40 psi at idle. I have noticed that after the longtube install when I take my foot off the gas from WOT that it pops (backfires) through the exhaust. If that has anything to do with this. It also has a very very slight stumble off idle if you stab the gas to the floor. Normal driving I never see this but if you stab it really quick it hesitates for a fraction of a second before taking off. Almost like the motors getting too loaded with fuel or somthing.

 

if it backfires when your let off the gas. you're probably running rich.

atleast, in my expirence.

 

The VERY first sign of my opti failing was the stumble. Not when i would regularly be driving it but when i would stab it, it would stutter and eventually get on it. I'd get it checked out.

 

You put new O2s in right?

 

the popping when u let go of the gas happens on a lot of cars after the cat is gutted. i dont think its ur opti. Maybe lack of backpressure is hurting ur low end, but then i would expect this to be a much more common prob. I wish i could help more, I hope some more experienced memebers can come up with more ideas

 

I was just talking with Ion (Madwolf) abouta tune and I "think" I have found my problem. At the same time I did the headers I added moroso cold air, a trickflow elbow, and also descreen and ported the MAF ends. I know this is a highly debated topic but I think this is might be where some of my problem is comming from. Or whats causing the stumble anyway. Now Ive got to find some stock MAF ends.

 

I was going to refer you to madwolf to get it tuned after your new round of mods. It could be false knock from the headers slowing you down. You did not mention the difference, or lack of, the weather conditions. I would recommend madwolf he does good work and is good to deal with. Get the mail-order it is worth it no doubt.

 

also since you have added headers you definitely need an LT4 Knock module to replace that stock LT1 KM

 

How about your 02 sensors, i know i used my old ones when i got my LT installed and they are totally dead now.

From what i have heard if you put in ur 02s right after new headers then when the headers go through there heat cycles they put off some funes and gunk that mess up your 02 sensors.

So i would say get some new ones if you havnt already

 

i was thinking lt4 knock module from the beginning when i was reading this post. could very well be false knock slowing you down..