zeetwoeight

This is my first post, and I have looked for this issue on the forums for a couple of years, have found things similar, but not close enough.

So here's my story, after I came back from Afghanistan in '07 I needed a car, so naturally I get myself a '01 Z28. I bought it second hand, with only 54k on it. the owner told me he babied it and always shifted under or at 2k rpms. I get the car home with no issues, only to notice that the limiters are on and that damn skip shift. So I start looking up how to disable skip shift and a super chips flash paq links comes up. I take a look, see that it has everything I need to disable skip shift and the speed/rev limiters. Being a young kid at the time, I just wanted to get the best performance I could for the price, not knowing that the flash paq was for bone stock cars only.

Now I can't remember if the previous owner had the car tuned or not. If so the flash paq would have scrambled the old tune right? Problem?, maybe...

I also got myself a Magnaflow exhaust, (catback), tires that same year. The car already had a SLP lid and Maf with functional ram air hood.

So besides those few mods, everything else is stock. Every since I got the flashpaq I have noticed this "noise" when I step on the gas at any amount of throttle, some times it never happens at all, some times it all the time. I have brought it to the dealership and had it scanned/diagnosed. Only thing that came up was apparently the fuel wasn't good enough. Even though I was at least 91 from Shell or other big name brands, had the fuel system flushed, fuel filter changed, spark plugs changed, knock sensors changed. Even Seafoamed it recently, only one cloud of smoke came out when I stepped on it so it was fairly clean. I've used fuel injector cleaners, octane boosters, all that stuff you can buy.

Sometimes when I start the car it makes a "snort" sound right as it cranks over..?

One of the mechanics that I brought for a ride to show him the sound said it was detonation. So I started trouble shooting on that, checking these forums for everything about it. If it is detonation I still haven't fixed it. The sound is a metallic sound, like a spring being stretched out, and I mean like stretching it to the point the spring is ready to break. (I remember hearing and seeing a rusty spring being pushed to its's limit as a kid and that "pinging" sound it makes reminds me of it) That's the best way to describe it.

I've tried almost everything I've read on here, asking the car guys about it. Cleaning sensors and anything I could do to clean/fix/repair/replace. The only thing I haven't done, is get it tuned or re-tuned if it was in the first place.

I always have had the problem with one of a kind issue's, ghost in the machines...

If anyone has an idea what it can be or needs more info please ask.

flattusmaximus78

iTrader: (1)

Bolt on's, low octane gas, and no tune... you probably have detonation my friend. Get a scan tool. Log knock retard. If you step on it and it measures any timing being pulled out; well then there you go.

A tune is going to be needed if this is happening.

Also catch can to stop oil from getting into the intake through the pcv for the future is good too.

zeetwoeight

I'll try going to the local Huskey, I've been told they have 93 octane. I forgot to mention I do have a catch can as well.

I do have a app on my phone called Torque and reads codes and what not, but not sure without hooking up to the ecu if I can log knock retard. Do you have any idea what numbers I should be around for the timing?

I been looking at a few websites that do the email tuning, so I may be doing that soon.

flattusmaximus78

iTrader: (1)

It should read zero. It measures degrees being pulled out. With your mods, the car is going to be leaner. I wouldn't go out and start doing a ton of pulls. Get on it real quick and see if it pulls timing when the sound is made. If so, you know where to start.

Email tunes work great for these basic mods. You can get a tune for your specific mods, and for 91 octane.

And a catch can is a great start considering you have one. Even if 93 octane kills the sound I'd get it logged and get an email tune. Some cars have audible knock and others don't so be careful.

Marc 85Z28

iTrader: (8)

Get rid of the SLP MAF and install a stock replacement.

gm02ceta

iTrader: (9)

Yep, I'd try this especially if it's an 85mm maf without proper tuning.

zeetwoeight

I will put my stock MAF back on today, should I take the negative off the battery and let it reset the cpu as well?

zeetwoeight

I had my torque app running on the way home from work, there was no knock retard for me to see, however I did see the advance timing at idle was between 19-24. Should that be normal?

fruitsalad

iTrader: (5)

I have what I think is a similar noise to what zeetwoeight is describing--it's really really faint and only occurs under heavy throttle. I datalogged while getting on the freeway under said heavy throttle condition and got some knock retard (3.xx degrees, I think) from something like 4300rpm-4500-then back down to 4200 and then it stopped. I did hear the noise faintly.

Am I leaning out under heavy throttle?

I'm running on California 91 ****, untuned with stock motor. I'm assuming the car was previously run on 93 only since I got it from out of state.

01WS6/tamu

iTrader: (37)

Trash the SLP MAF put OEM MAF on. Then take the car to your nearest gm dealer and have them reflash the pcm so you have a known stock OEM starting point and see if the problem goes away. If noise goes away then call any sponsor to the right and or a local LS tuner and go get it strapped down and a dyno tune done on it. Put the programmer in the trash can where they belong.

zeetwoeight

Like fruitsalad said, it is a faint noise under the same conditions, very rarely it does it at less rpm. I just might be paranoid about the noise so I'm constantly listening for it. But I have noticed it won't make any noise when the engine is cold, on the hot days its more constant. Can't hear it if the windows are up or radio is on. I have the stock maf on and haven't taken it out to test it under load, and I don't want to until I get it on the dyno.

fruitsalad

iTrader: (5)

FWIW, the previous owner of my car used a Hypertech programmer and had the car set on "performance tuning." No details as to what exactly that "tune" was. I set it back to "stock tuning" and reprogrammed. The sound was still there after the reprogram.

Could it be a worn out fuel pump unable to keep up at high rpm? I know of a few reasons why the fuel pump might be worn out. I don't notice a significant loss of power, but I also don't really have a reference point to determine whether it's slower than it should be.

I have the stock maf and all that already.

zeetwoeight

Just a tought, would there be any back pressure from the Magnaflow cat back exhaust making the noise I'm/we're hearing? 3 inch going into the muffler 2.5 inch coming out? I'm not thinking it would be the issue.

fruitsalad, I have done the same thing with the superchips flashpaq I had, it all seemed to start then, but having a new exhaust installed around the same time I can't say for sure what the cause could be, if it was either of those.

I need to replace my cats since they are gone and putting up the code for the last month. Was thinking of getting a muffler with 3'' in and out while I'm at it. As well as looking into getting a Diablo sports intune.

Has anyone used or have one of those programmers that can input on here?

fruitsalad

iTrader: (5)

double post due to shitty internet

fruitsalad

iTrader: (5)

I have some generic Flowmaster muffler that the previous owner installed and, AFAIK, otherwise stock exhaust with plenty of dents and scrapes.

Sounds like it's something to do with these shitty canned tunes. I'm thinking of doing TSP true duals and then a mail-order tune.

RevGTO

iTrader: (12)

Hypertech "performance tune" advances timing and can cause detonation. Happened to me when I first started experimenting with tuning and I had to revert back to stock.

I'd follow the advice above and get the PCM reflashed to stock tune and go from there.

MillsMotorvation

Its not coming from the engine so stop looking there. More likely coming from trans. bad mount, Torque arm, shock, springs....ect . Good luck!

zeetwoeight

Would I just be checking for anything being unsecured? Loose? or touching another something else?

zeetwoeight

On top of replacing the cats I need to replace the knock sensors again, getting AC Delco and harness just because. Loving this upkeep....

MillsMotorvation

Ive chased that noise before, and it was the rubber boot the spring rest on. Just look for some thing loose, or rubbed. Hard to say. Had a rear rubbing the exhaust when the car excels, could be anything.