ScubaSteveZ28

I've got a 94 Z28 M6 that has lost power and has gotten quieter over about the past month.
Mods:
Ported LT4 heads and intake
LE 227/235 cam (installed 12/2013)
K&N CAI
Edelbrock mid-length headers
Borla exhaust
PCM4Less tune (done when the LT4 Hotcam was in the car)
Accel 30 lb injectors
MSD Optispark (installed 03/2014)
There are others, but I believe these to be mods that might have to do with the issue.

It ran great after the cam install, smoothed out after the opti install, but began having the issues soon after. I ran a compression test...190 psi was my lowest, 205 psi was my highest. Most of the plug electrodes were light gray (running lean, if I remember correctly), but the threads had quite a bit of oil on them. Fuel pressure test was 35 psi at key on and 43 at idle. Do I just need to get the car tuned again or do I have bigger issues? Any ideas or suggestions would be greatly appreciated!

SS RRR

iTrader: (2)

Maybe you're just getting used to it? How do you know it's lost power?

myltwon

iTrader: (1)

The fact that you have accell injectors and are witness a lean condition I would lean towards them, best way to know if something is wrong is to log the car, dyno it, or run it at the track.

ScubaSteveZ28

I can't break the tires loose at all anymore. I used to be able to hit it in first or second and lose traction. I've considered replacing the injectors...they are 10 years old now. I've just gotta come up with $200-300!

hrcslam

A Set of 8 30lb EV1 injectors are on Ebay for $140 all day. 36lbs can be found for $90 for a set of 8. If you are not already running a tune for Bosch injectors you'll need one if you go with those though.

ScubaSteveZ28

UPDATE: I ran all the intake manifold bolts, and it felt better (still not 100%) for a short time. I pulled (and replaced) all the plugs - TR55 gapped at .050, and they were all gas soaked this time. It runs terrible now, and has gotten even quieter.

SS RRR

iTrader: (2)

Is the PCM tuned for the 30lb injectors?

hrcslam

This^

If you didn't tune the car after the Injector swap (or everything else you did) it will not run right. The injector timing is very important on these.

96capricemgr

iTrader: (1)

So the tune is for a different cam with stock heads?

The MSD opti causes at least as many problems as it solves.

OLD Accel injectors were known to be BAD BAD news like burn cars to the ground bad.

Did you use a stock gasket for the heads? I would expect more cranking compression from a heads/cam setup if you had used a reasonable thickness gasket.

Kevin97ss

Sounds like a clogged catalytic converter.

ScubaSteveZ28

The tune was done for all the mods listed except the cam. It had an LT4 hotcam at the time.
I think the compression numbers are low because I didn't have the throttle open. I remembered after the second cylinder, and just decided to keep going and do them all the same way.

ScubaSteveZ28

UPDATE 2: I pulled the cat off. It looked fine. I drove it around the block, and it acts the same (other than the increase in noise).

FormulaJoe

iTrader: (5)

Dude compared to a hotcam your cam is way bigger. Your tune is definitely the first thing you need to update and don't drive it until you do so. The tune is probably where most if not all your problems lie.. Changing a cam to anything other then what GM put in a stock lt1/lt4 motor needs to have a re-tune. Trying to diagnose any problem you might have besides the tune is pointless until your computer is tuned for your specific application