bbarr43

Hello all, I'm scratchin' my head on this. Got cam & heads w/ mods in sig, should get 400+ HP. Car is inconsistent here, recent dyno tune at Reckart only got 366 HP. Was getting P0300 & P0155, replaced front o2 sensor, codes cleared, no more SES light. But, Check Gauges lights come on randomly at start up, with no fuel, no temp readings & oil change light until car warms up. Car stalls regularly w/ A/C on at idle. Yesterday, using Torque Android app, I got 390 HP at around 5000 RPM, car felt great kinda scared me. Today, only gets 320 HP at 5200 RPM, feels real sluggish. Does this regularly. What gives? Sometimes it's a beast, sometimes it's a kitten. Spark plugs are good, and MAF is clean. HELP please!

BigBirdLS1

Get a good tune...a car shouldn't die EVER when you turn the A/C on even at an idle. If I was a betting man all of my $ would say your tune needs tweaked...alot

ReCoil

iTrader: (3)

Yep, sounds like your tune needs work. I am going through similar issues with my 383 stroker, with regards to the A/C stalls and weirdness before it's at operating temps. My tuner is taking my car for a couple days next week so he can drive it and tweak the tune to get it perfect so my driveability will come back. Sounds like you might get with a tuner and do the same.

bbarr43

Thanks for the reply guys. Well, he's supposed to be the respected LS guy to see around here. He stopped tune at 366 HP, said my 26# injectors were at 98%, and of course random misfires. Somehow I thought those were still good over 400 HP though. He thought my cam timing may be off, but when installing, I spun it several times around after lining the dots up. Could the bad O2 sensor thrown it off at all? wouldn't think so at WOT. ReCoil, keep me updated on yours man.

high impact

iTrader: (5)

So he recommended to you to install larger injectors and bring it back to finish the tune?

bbarr43

Yes, he did recommend larger injectors and then bring it back. Somehow I don't think upgrading those is the real issue right now. Unless maybe bad/clogged injectors. It's noticeable random performance difference. Sometimes I give it light throttle, it really moves. Other times, feels like it's choked or not firing on all cylinders. Do PCM's fail on these? Wondering about my check gauges lights coming on.

bbarr43

So I replaced all spark plugs yesterday. Previously had NGK TR55IX, replaced with NGK V Power at .040 gap, just for a cheap solution. So ruled that out, car seems wimpier now. Car also initially had trouble starting, seemed like it was flooded. I noticed the CTS on head had a crack on housing, so the harness slipped right off. Will replace that today and post back.

SKINNY69

Your tuner already told you that you're maxing out the injectors... What more do you need to know?

BobDoLe

iTrader: (11)

i doubt his stock injectors are maxing out at startup, idle or when he turns on the AC. sounds like the tune or a sensor.

bww3588

iTrader: (49)

If the coolant temp sensor is broken, that will cause all sorts of problems. If I remember correctly, when the cts fails, it defaults to -55 degrees and just dumps fuel in to protect the engine. With air temps reading ambient or normal and the computer seeing ridiculous water temps, I'm sure it's throwing things all out of place.

It also agrees with his statement of one day it's fine, the other it sucks. If the connections are loose, that would cause exactly that.

bbarr43

Thanks for the input guys. Found out a few things, replaced the CTS after 5 tries. Unbelievable how bad this is to find a sensor that works. Got 2 AC Delcos, Duralast, BWD, finally Delphi TS10076 sensor on Amazon (only one that worked), lol. On another note, had a bad PCV valve, resistance on both ends. Also, intake manifold bolts were very loose on passenger side, so pretty good leak there. Tightened those down, and man.. top end power is really back now. Think the PCM is still recalibrating a bit, but she's ripping the tires on light throttle now. Might go ahead and upgrade the injectors and go back for the tune.

high impact

iTrader: (5)

Sounds like you are getting somewhere now. I agree with double checking all maintenance items, installing larger injectors and bring it back to the tuner. Really watch that fuel pressure as well to make sure you don't have a pump on the fritz.