Is it a common problem for c5 to have detonation at WOT? I'm in CA and 91 octane is the standard highest octane. I hear detonation when going WOT around 4-5k RPM. Yes, the marble in tin can noise. The first few times I thought it was rocks around the wheel wells.

I don't want to blow my motor because chevy didn't tune it to CA octane specs.

Anyways what is the fix for this? I searched and did not find an official fix though I see a lot of people suggesting a tune, but do not see any one comfirming.

 

Have you changed spark plugs? Proper gap? You can add an octane booster and see if that solves it. Then you will know you need some tuning to get 91 to be sufficient.

 

The LS Engine PCM (IF FUNCTIONING CORRECTLY) will reduce timing and or shift to the LOW OCTANE Tables if the Knock Sensor senses any DETONATION.

Unless something is really wrong, you shouldn’t hear ant KNOCK/Detonation!

What modifications have been done to the engine/PCM?

Do you see any Check Engine lights or messages when it happens?? Some tuners tune out the DTCs and warnings that can warn us of issues.... Has your PCm ever been tuned???

Please read and post your DTCs

Here’s how:


READING YOUR Engine Diagnostic Codes


READING YOUR Engine Diagnostic Codes



The Diagnostic Display Mode is entered with the following procedure:

1) Turn on the ignition but don't start the engine. NOTE! You can read the DTCs with the engine running and or driving down the road but it can distract you. BE careful! Some DTCs clear themselves when you turn the ignition OFF!

2) Press the RESET button to turn off any warning messages. (i.e. door open, trunk open ect)
3) Press and hold OPTIONS
4) While holding OPTIONS, press FUEL four times within a 10-second period.


Initially, on-board diagnostics go into an Automatic Mode which shows diagnostic codes in a pre-set sequence: PCM - TCS - RTD - BCM - IPC - RADIO - HVAC - LDCM - RDCM - SCM - RFA. All codes will be displayed for each. ( i.e. PCM = 4 codes) If none are present in a given module, you will see No More Codes on the display.
There are two kinds of diagnostic codes, Current and History designated with a letter suffix, “C” or “H”. A current C code indicates a malfunction is present and active in the module displaying data. A history code indicates a problem existed sometime in the last 40 or 50 ignition cycles. When not accompanied by a current code of the same number, it's potential evidence of a previous problem, now resolved, that was not removed by clearing the codes.
More likely it's an indication of an intermittent malfunction.
Intermittent codes are the most challenging of the diagnostics. An intermittent code may have happened once, may have happened more than once but is inconsistent or may be happening on a regular basis but not at the time the codes are displayed. History codes can also be caused by a current malfunction in a system that is not operating at the time codes are displayed. An example is the rear window defogger which doesn't operate until the Body Control Module detects engine rpm. For history codes set by a module that does not operate with the key on and engine off, a special diagnostic tool called a Scan Tester is necessary to properly diagnose the malfunction.
Once the system has displayed all modules, it goes into the manual mode which allows selection of each module using combinations of Driver Information Center buttons. Manual mode can also be entered during the automatic sequence by pressing any button except English/Metric (E/M). Once the display shows Manual Diagnostics, select a module by pressing the OPTIONS button to go forward or the TRIP button to go back. Once a module is selected, a code is displayed, and if more than one are present; press GAGES to go forward or FUEL to go back.
To exit the diagnostic mode at any time, press E/M. If you want to erase codes in a given module, press and hold the RESET button To reset the codes once in manual mode, press and hold RESET until it displays NO CODES Press OPTIONS to go to the next module. Repeat the steps until you have reset the codes in all the computer modules.
NOTE!! Only reset the codes IF you want to - it is NOT necessary to do this. Clearing a code does not repair a problem. You are simply erasing the evidence of it in the module's memory. If you clear the code/s, and extinguish the Check Engine Light, your emissions status ready will NOT allow you to pass an emissions test until you have completed the required driving cycles.
Once you have the codes, the next question is: What to do with the information?
First, consult the factory service manual. Any serious C5 Do-It-Yourself owner should invest in the Corvette Service Manual of the appropriate model year. The Service Manual is really a requirement if you want to understand and work on your C5. You can GOOGLE the DTC and also find information on it.




Here is very good site that explains the DTCs:


http://www.corvette-web-central.com/C5DTCcode.html


http://www.obd-codes.com/trouble_cod...d-ii-codes.php



Make sure to include the H or C suffix!!

 

My detonation issue was solved by a 3rd gear cruise on the highway with a few good hard pulls. Haven't had any issues since

 

What year is the car and what mods are done to the car if any? Any way of scanning the car? you should not be able to hear the detination, the computer should pull timing out well before you get that much detination. If you have the means then you might want to invest in some sort of scanner.... you can get universal ones that show basic info, Applications for a smart phone w/ bluetooth OBDII adaptor. I would start by scanning to see what the ECU shows.

any chance what you hear is just a metallic rattle/jingle not detination?

Stock motor with stock ecu i would start with:
* New Plugs (Irridium) and Wires (GMPP)
* Replace fuel filter (depending on if its pre-03)
* Fuel system cleaner (I like BG44K)

 

My 2004 Z06 has detonation too. All stock. California. Just the way it goes. If it gets to bad, I'm going to add Torco for my autocross races.

Steve

 

Couple of things to check out.

What is your coolant temp when its having issues?


Have you ever done a engine top cylinder cleaning? That can help remove any built up carbon.

Data Log the engine and look at the followinng:

Long Term Fuel Trims (LTFT)
Knock Retard KR / (Spark Knock)

Bill

 

The number one cause of audible spark knock that I've seen (stock tuned/stock airbox) is a bad Maf. As it will under report the airflow (cylinder airmass), thus over advancing the spark timing causing the spark knock. Plus the fuel trims go very lean (positive).

I would scan the car with any basic scanner, if the fuel trims go high and or the WOT S1 O2's mv drops really low, then the Maf is bad.

A quick test is to unplug the Maf and scan the fuel trims & WOT S1 O2's mv. If the fuel trims & WOT O2 mv are normal, then replace the Maf.

Russ Kemp

 

Might also try cleaning the MAF before replacing it.

 

Good recommendation Russ. Thats why I Data Log...

Best way to figure out the cause vise throw money at Easter Egging parts.

Bill

 

To the OP, Russ's advice above is good, that's exactly what happened to my car.

 

I lived in CA a few years ago. My car sounded like Uncle Buck's car... the problem was using Bosch plugs. Switched back to AC Delco and all was well.