ssjunkie

iTrader: (3)

Ok, So for the past few days(week) the Maggied V has started detonating anytime I lug it a little. As in roll-on the throttle with the RPM's at like 1800 in 3rd. It sounds horrible...I immediately let out of it. I initially suspected a bad tank of fuel. Well, I just filled up with 16 gallons of Sunoco 93 octane and its still doing it. I havnt done anything to the car. Im not even sure where to start? I have no SEL or anything. Knock Sensor? Any other thoughts?

John

punishmentcycle

iTrader: (6)

didnt you just do the rear pulleys and sd tune? might be someone else im thinking of..correct me if im wrong.

i had a similar issue but it was only in 6th at 1800 or so rpms. if say id leave it in 6th and just roll the throttle to pass a car or something i would get 3 degrees of knock..we narrowed it down to too much timing on tip in..pulled a few degrees in the lower rpm range and problem solved

ssjunkie

iTrader: (3)

Nope not me. Still stock pulleys here. I did hade a re-tune at RPM about a month ago. But it was fine for a couple weeks...at least I think it was. I didnt notice it till recently. I need to go back to RPM for some fine tuning (idle characteristics) maybe im going back sooner than later.

punishmentcycle

iTrader: (6)

ah thats where i remember you. did you go back the second time and have them fix the tune? if not i wouldnt wait any longer. you can put some torco in there for now but make sure you run a couple tanks of clean gas thru is before you retune.. itll keep it from knocking for now.

as far as tuning for drivability and idle and all that i would not bother doing that stuff on a dyno. its best to have the owner or primary driver of the car, drive it while the tuner logs and makes changes based on driving habits.

ssjunkie

iTrader: (3)

Have not been back yet...but moving it up on the priority list!

Ok, so heres a question...how long would it take for the gas(maybe bad gas) to circulate from the fuel line and mix with the 93 in the tank? I only went maybe a mile before I tried it after leaving the station. It was less than two miles home from the station total.

John

punishmentcycle

iTrader: (6)

not long at all really. it doesnt sound like bad gas. bad gas will will give you problems everywhere in the rpm range. you either have too much timing down in the part throttle/lower rpms or something mechanical

DMM

This is something you really have to data log to see what the PCM is doing and why. While it's possible that you could have gotten contaminated fuel 2x in a row, it's not very likely. It's even less likely that something changed in the tune, so it's really going straight to the data for an answer.

itsslow98

iTrader: (18)

Have you pulled the plugs to see how they look?

ssjunkie

iTrader: (3)

No, I have not checked the plugs yet. I did just put the plugs in about a month ago. thread is here - Plugs change thread. That was right before my tune which is threaded here - Tune Thread

After the tune It was not detonating, I even went to Capitol Raceway - threaded here.

Anyone local(Anne Arundel County, MD) able to log some data for me to see whats going on. I don't have a cable or software right now. I'm willing to compensate for your time.

John

punishmentcycle

iTrader: (6)

Have you checked for leaks in the intake tube. Any leaks after the maf will send it insta lean

ssjunkie

iTrader: (3)

So I just got back from RPM...Turns out it is not detonation. I was in the car with Fran and live data going across the screen on the laptop...he induced the noise by hitting the gas pretty hard with RPM's below 2K in 5th. There was no knock sensed. Fran's conclusion...most likely a belt tensioner. So that brings up another question. Is the tensioner a stock one with a Maggie or a special one from Magnuson? Or is it the A/C tensioner...I can test the A/C one by removing the belt and seeing if the noise goes away. think thats where ill start!

ssjunkie

iTrader: (3)

So after some messing with the belt and tensioner...I could not find any problems. I had a mechanic friend ride with me and we both agreed that it was likely that my original diagnosis of detonation was probably correct. So I bought a bottle of octane booster. The noise is gone now. So now I think im going to swap out the knock sensor. Since the computer wasn't seeing any knock.

Another question is...should the tune be relying on the knock sensor to pull timing? Seems to me maybe the tune must have to much timing in the table in the lugging condition.

Frans96SS

iTrader: (15)

I HIGHLY doubt that it was actually knock.... It was WAYYY louder than actually knock would be.. I will absolutely look at it again but i really dont think its knock. Knock sensors were working fine bc it would pick up bits and pieces of knock hear and there.