Well if you followed my saga of my car, '95 Z28 A4/2.73 car and its mysterious losing performace. well I just got back from the track. after changing tranny fluid, putting a 160 degree 'stat in it....the car still is slower than stock. Two years of this crap, changed everything and nothing worked. Final thing I never checked was fuel pressure, checked it tonight after getting back from the track. 36 PSI at idle, with regulator disconnected it jumps to 46 PSI. So its official, even with new wires, plugs, fuel filter and every other darn thing my car went from 13.6's to 14.0's and lost 3 MPH in the 1/4 from two years ago. Darn thing is gonna sit in the garage now I'm sick of it, cherry car with only 62k miles on it its a damn shame. Hopefully this summer I can get an LS1.

 

i feel you pain

 

Is your intake manifold sealed nice and good? Changed 02's? Changed pcv valve? plugs and wires? cleaned tb? just check because these were the things that made the diff in my car. was super slow when i bought it. Biggest change was with cleaning the TB and the intake manifold leak.

 

Hmmmm, noticed your post doesn't say what you have done to kind of car you have. Try cleaning off the wires in the MAF. bet they are dirty ?

 

T/A #4 here is my original thread

http://web.camaross.com/forums/showt...hreadid=259064

As far as the other stuff, plugs and wires are new, intake manifold seals perfectly (none of the infamous leak), TB was cleaned recently. I'm telling you I've done everything you can imagine. Its bizarre. The only way to go now is to just start throwing money at it and I can't do that.

 

my car is doing the same thing.
It seems like the entire powerband was shifted down. I have great low end power, the engine idles great, sounds great. but at the track it falls flat on its face after the 1/8th mile marker and my 60' times are worse than before. I have no idea whats going on. time to go back to an older setup to see where I went wrong.

 

Like I said I've had it with the car. The only things I can think of are the plug wires maybe being defective.......but you'd think I'd detect a miss somewhere. The car starts and idles perfectly and pulls cleanly. The other possibility is a transmission going out. Well I just swapped fluid out that had been in there for over a year and 10,000 hard miles. It was a perfect red color and just a tiny shade darker than new fluid. Smelled perfect too. I've had cars with trannies going bad and burned fluid is the first clue. I need to have it scanned but even if I find the laptop, cables and software for killer prices I'm still talking over $500 for the POSSIBILITY of finding what's wrong. F-that...........$500 into my DSM puts me alot faster than this car is. My Camaro can become my daily beater unless I can sell it locally here.

 

Wouldn't surprise me if the PCM is retarding timing a WOT... there are a couple things that can cause that: false/real knock, a sensor out of whack, etc.

Find somebody local who can scan it (try posting on one of the regional lists). If you get desperate and feel like driving ~4 hours down to my place (DC area), I'll scan it for you... email me privately.

 

Last week m car went from 12.2's at 109 to 12.8's at 103. The loss was consistent across the powerband. I could not hear any rapping r ticking, plug wires were tight, plugs were new, new opti, new alternator, new ICM....

The sixty foot time was off by a tenth, 1/8 mile split off by 4 tenths...

What I found were two broken pushrods...

 

How about you take your car down to F-Body Centeral in Maryland. Most of the people on Eastern F Body will recommend them. Their number is 410 242 0404. Also you could try a compression test. I know your details but if you get the tool which is cheap (i think) then it wont hurt anything.

 

Timing chain could be stretched and pulling timing out of it.
Ron

 

Hey Baron, what happened to your 60' times? Do you have the stock differential?

 

& somehow disconnecting your vacuum hose tells you your fuel pressure is good? Did you know that at WOT & 6k RPM your injectors are at 90+ duty cycle where the fuel pump might be having trouble keeping up? while at idle it'll give you all the PSI in the world because your injectors are basicly closed?

 

I agree. I was looking for a new fuel pump among the parts you replaced, but didn't see one listed.

 

one other thing - as you have a 95, you can purchase a cable from Andrew Mattei (AKM cables) that will hook your car to a computer for about $60, then download some free scanner software and scan everything yourself. Since its a 95, you have OBD1 not the super expensive obd2 setup. check out http://www.akmcables.com/ (note that you CAN hook it up to a regular desktop, you don't have to have a laptop computer...)

I agree about the fuel pump, an idle test really doesn't show how the pump is working all the time. Get a longer line and gauge on it, duct tape it to the windshield and go WOT, see where it is then.