ive had my car for a few weeks now. the guy i bought it from is pretty reliable and straight up, bought my old car from him as well. anyways he had a Nitrous works plate system on the car with a 125 shot, and that was pretty much it. had a WOT switch and arming switch that he hit when the car was about 3,500k id say. so he didnt have window switch or FPSS and he sprayed at w/e bottle pressure (no heater or gauge or anything). anyways to the point, ive been noticing a small knock when i accelerate. i usually have to give it a little more than normal acceleration but not much more. it sounds like marbles or something, kinda quiet, but definitly noticeable and it seems to be only happen/ be much more evident, when the car is cold. it has a 160 stat and TB bypass so it runs very cold in chicagoland weather. i was wondering if maybe anyone had any ideas or thoughts about as to what this is. could it possibly be detonation? BTW, i havent fully laid into it yet and gone through the gears but there are no signs that it is down on any power at all, seems very strong. any help would be awesome. thanks

 

Sounds like you need a tune. Those marble sounds are not good and everytime you here it it puts wear on the engine.
Im guessing you are talking about this happening NA and normal driving. I would start with checking your spark plugs.Then take it and have the tune looked at.You may be running lean or just to much timing.If you are not running super unleaded try that.If you do not have a tunner in yuor area I always use Moe Baily.He does mail order tunes also.If you need his number feel free to pm me.
Dave

 

well i was setting up a full exhaust with longtubes and what not and then i was gonna get a full mail order tune from MadZ28. should i save the money and just go right to Speed INC and have professionals actual get their hands on it? but that is a lot of money i have a feeling.

 

Unless the previous owner disabled the knock sensor there is no way you will hear detonation. The sensor prevents it. Check with him.

Like Dave said check the spark plugs for black or silver specs.

Otherwise maybe you can hear the rocker arms, I'm guessing oil pressure is good.

 

my old car was a 93 Z, it was quieter than ****, except the exhaust. that ran excellent. this car will walk that car and pulls like hell, only difference is this kinda has a knock. im thinking maybe its somethign to do with the cold. its been around 0-20 degress outside. oil pressure is awesome, if i beat on it i wait till about 170 degrees just so i know the t-stat is open. i havent looked but im damn near sure the knock sensor is still connected. this is what he said about the plugs"I put new Autolite 103 sparkplugs gapped at .035". im not sure if those are nitrous plugs or what. this car really does seem to run awesomely and it doesnt miss or anything, just sometimes that knock. any more ideas? you guys think it would be fine to go ahead with my longtubes/y pipe and maybe check the plugs while im doing that?

 

You can still get knock if your tune is WAY out of whack. The knock sensors will sense knock and pull timing...but it only has so much authority as far as I know. If the tune is way off the timing pulled may still not be enough to prevent 100% of the detonation.

You could put a few gallons of 100 octane in it and try again. If the knock and pings subside...its likely detonation. If not...look for somewthing mechanical as stated above.

 

will a basic mail order tune help out? i know they are supposed to help with performance but will it help get things correct in the computer if it really does have a messed up tune right now? basically im asking if this needs to be a trial and error thing like pull timing and run it etc...

 

I dont really see a reason, based on your mods, why your tune would be SO off that it should still knock taking into acct that the computer will sense knock and pull timing. This means you would have to be WAY out of whack to still have detonation.
I would not get a tune just yet. I would also not beat on the car just yet.

I would get 5-7 gallons of 100 octane unleaded and put it in the car to see if detonation goes away. If it does a tune may fix you up.
I would also check your fuel pressure to see that you dont have a dieing pump or some other fuel issue. If so fix that first.
If possible then get a dyno tune with a good tuner so he can see your AF ratio and adjust it as required as well as timing

 

i just seem to think that if there was somethign wrong with the tune/fuel etc... the car would run like crap. right now if the noise wasnt there you wouldnt suspect anythign was wrong at all.

 

but if the noise is actually detonation...believe me...its running like crap. LOL.
It really means either too little fuel or too much timing for the parameters the car is operating under. Several things can cause that.

And if it detonates on motor as you describe...it will likely be catastrophic if you spray it.

 

alright. i just requested a qoute from Speed INC. im gonna see if they can just check it out and maybe see if everything is alright in the PCM itself and other stuff. a full dyno tune is 500 bucks from them, but if they tell me its something really simple ill just continue on with my exhaust and mail order tune plans. we'll see. thanks guy.

 

Man it sucks to have to pay that. But it will help you down the road. One thing though. Dont just take it in for a tune and drop it off. Be sure to tell them that is seems you are detonating and that if necessary you will get a tune to correct that if thats the problem. May want to have them look at it and scan it first to see if its something simple and NOT tune related. If something obvious doesnt jump out at them...if there is a mechanical or sensor issue that is causing this...they will likely uncover the problem during the tuning process. So hopefull its money well spent. Good luck!

One more question...do you have any SES or check engine lights?

 

nope SES never comes on at all. i just got an e-mail from Larry at Speed INC. he said they can have a look at it and tell me their best guess. so i asked what it would cost if anything to have them check it out and what it would be to actually scan it etc. it just seems weird cause the car seems like nothing is wront at all, just the stupid knocking. ill see what he says and maybe ill take it over there sometime. thanks again

 

Good deal. Hope its something simple first. But even though the car isnt terrible...the knocking needs to be fixed before you proceed to nitrous. Youll be glad in the long run when the car is running right and making great power.

 

Seems unlikely that a "great running" stock car, operating in sub freezing weather, with a cold stat, and a bypassed throttle body, all anti-detonation, would produce any, let alone audible detonation.

I was barely able to confirm (hear) audible detonation under moderate acceleration, lugging the car in high gear, with a hot engine, with 50-60 degrees advance forced into the ignition advance table. And only with the laptop hooked up monitoring knock count and knock retard for verification.

I doubt you're able to hear detonation with a correctly functioning knock sensor and stock programming. The computer just doesn't allow it. And, the dynomax muffler would make it almost impossible. The car runs good, the computer is working.

The computer is capable of pulling 15+ degrees timing under various operating conditions using many different criteria.

You should find the rattle, since it bothers you, and before you beat on the car. Check the plugs, it's free. Buy an AKM cable for $50 and use freescan (it's free) to look at knock retard and count.

I'd look for a loose heat shield or something else that's about to fall off.