My car seems to have detonation problems, under hard acceleration in 1st/2nd gear, i get the rocks in a coffee can rattle sound from the front of the car. It seems to be detonation. i have been told to put an octane boost bottle in the gas and also a fuel injector cleaner. (did both but on separate tanks.)

What could be causing this and what can i do to fix it?

THanks for the help.

 

Pull your codes and post them and I'm sure you will get a lot of answers

 

The only codes im dealing with are the steering sensor/active handling codes that seem to pop up. nothing related to the engine.

 

If you were pinging, the knock sensors aren't doing their job. Any engine modifications?

 

The first thing to check is the PCM ground G106:


(1) G201
(2) G103
(3) G101
(4) G102
(5) G104
(6) G202
(7) G302
(8) G402
(9) G401
(10) G301
(11) G107
(12) G105
(13) G106

 

thanks but im not sure exactly what that means. can you explain?

 

Grounds probably have nothing to do with your problem. 1st you have to figure out if it's really predetonation pinging or some other noise. The engine is designed NOT to do this with 2 knock sensors under the intake manifold. The computer will vary the timing to stop this. The knock sensors are known to go bad so you should see if there are any pending or historic knock sensor codes. You might have a lot of carbon buildup that a "Seafoaming" might cure causing it but maybe it's a different noise. Search on Seafoam but basically you take this cleaners, pour it SLOWLY into a vacuum source while the engine is running, shut the car off for a while. When you restart, you may blanket your entire neighborhood with SMOKE from the cleaning process.

There are several reasons an engine can ping, you can Google it but generally it's too low an Octane gas (low octane = more volatile) OR carbon buildup on valves/pistons holding heat and causing the fuel to preignite OR the spark advance system is broken.

 

Sure. The PCM is the computer that controls all engine functions. If it is not functioning properly all sorts of bad things can happen. The grounds in the C5's are notorious for corroding and losing a good connection. This is the first thing the service manual recommends checking. The diagram I provided you shows where the ground connections for the PCM are located. You need to check to see you have a good, clean connection.

There is a Sticky at the top of this page written by Bill Curlee that describes cleaning the grounds in great detail.

 

Here are the basic steps to take to diagnose a detonation/ping problem from the service manual:

Preliminary Checks

* Refer to Symptoms , Important Preliminary Checks Before Starting.
* Search for bulletins.
* Check the PCM grounds for being clean, tight, and in their proper locations. Refer to PCM wiring diagrams .
* If the scan tool readings are normal (refer to supporting text of the Powertrain On-Board Diagnostic (OBD) System Check) and there are no engine mechanical faults, fill the fuel tank with a premium gasoline that has a minimum octane reading of 92 and re-evaluate the vehicle's performance.

Fuel System

* Check for a low fuel pressure condition. Refer to Fuel System Diagnosis .
* Check for a restricted fuel filter. Refer to Fuel System Diagnosis .
* Check for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
* Check the items which can cause an engine to run rich (long term fuel trim near -13%). For a rich condition, refer to DTC P0132 HO2S Circuit High Voltage Bank 1 Sensor 1 and DTC P0152 HO2S Circuit High Voltage Bank 2 Sensor 1 .
* Check the items that can cause an engine to run lean (long term fuel trim near 23%). For a Lean condition, refer to DTC P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1 and DTC P0151 HO2S Circuit Low Voltage Bank 2 Sensor 1 .

Ignition System

Check the spark plugs for being the proper heat range. Refer to Engine Electrical/Spark Plugs .

Engine Cooling System

Check for obvious overheating problems:

* Low engine coolant. Refer to Engine/Engine Cooling for the type and amount of engine coolant to be used.
* Restricted air flow to the radiator or restricted coolant flow through the radiator.
* Inoperative electric cooling fan circuits. Refer to Electric Cooling Fan Diagnosis .

Engine Mechanical

Check for the following engine mechanical problems:

* Excessive oil in combustion chamber-Leaking valve seals. Refer to Engine/Engine Mechanical.
* Low cylinder compression. Refer to Engine/Engine Mechanical .
* Combustion chambers for excessive carbon buildup. Clean the combustion chamber by using top engine cleaner. Follow the instructions on the can.
* Check for incorrect basic engine parts. Inspect the following:
o Camshaft
o Cylinder heads
o Pistons, etc.
* Refer to Engine/Engine Mechanical.

Additional Checks

* Check the Park/Neutral Position (PNP) switch operation. Refer to DTC P0705 or P0706.
* Check the TCC operation. The TCC applying too soon can cause the engine to spark knock. Refer to Transmission/Transaxle/Automatic Transmission .

End quote

There is also a service bulletin that deals with the rear knock sensor. It often happens when an owner frequently washes the engine. The rear knock sensor becomes corroded and ceases to function.

 

-Knock sensors are bad
-Carbon build-up in the cylniders
-Crappy gas

 

Might be worth checking.

 

The first thing that you need to do is give us some more info. Where do you live, what year C5, is the car stock, modified, high miles, low miles, auto or manual,,,,,,ect.....Up date your profile. You might find that there are people in your area that are willing to help.

Once you provide that some one in your area may scan your engine with HP Tuners or EFI Live and data log the engine while the problem is happening. That will tell you if it is really KNOCK or if its something else making the noise.

There are so many variables that it difficult to tell you where to start without more information.

 

Sorry,

The car is a 2001 ls1 M6 vert. I live in Phoenix area which is where the previous owner lived. currently has 98,000 miles on it, i bought it with 90K on it. the car itself is in really great shape. 1 previous owner and the car had a clean carfax. the drivechain was complelty stock when i bought it. i have added a K&N CAI and a borla stinger catback to it. when i got it i Cleared all the codes the car had. here they are:

TCS: C1281H
C1287H

IPC: B0521H
U1160H

A0-LDCM: B2252H
U1064H

A1-RDCM: U1064H

A6-SCM: U1064H

B0-RFA: U1064H

 

You might have an air leak from the CAI causing a lean condition-check all you connections on the air filter.

 

Have you tried changing brands of fuel?I know my car is sensitive to different brands,stay away from the cheapos!

 

I had suspected that for some time. I just needed to hear it from somebody else. I went out and switched the CAI back to stock and took the car for a spin. No more detonation. YAY!!!!!

The question now is: What caused this? I checked all the connections to the air filter and everything was tight. Was the filter letting in too much air and the computer couldnt control the AF ratio?

Thanks

 

Probably an umetered air leak coming in. The computer need to know how much air is coming in (usually a Mass Air Flow sensor on most cars), if you have an air leak past it somewhere, the MAF does not sense it and too much air is coming in for the fuel allocated-you get a LEAN condition.

 

I started having the problem a few months ago as well. Great post.

I have a bigger cam and heads and since she had those items installed can get up to 228 at idle with the AC on. However didn't notice detonation until this summer when she gets hot. The other summers not a problem. She has 43k on her now, so I'm thinking change out plugs and wires. I tried STP fuel cleaner and nothing. You guys mentioned other things to look for so I will.

 

People ask all the time if they need a tune from a CAI. The answer in your case is yes. The MAF only does part of the work. There is a table that predicts the amount of fuel needed based on engine RPM and manifold absolute pressure (MAP). The two work in tandem up to 4000RPM where the MAF takes over almost completely. That table I'm talking about is the VE table. It should be adjusted. A good tuner should be able to cure your issues with the CAI as well as extract another 20+ horsepower from your ride.

 

I had the same problem and this worked for me: Put in 1 12-gallon can of Techron, one can of SeaFoam, and filled tank with Texaco (with Techron). Still had proble after 1/2 tank of gas, so added another can of Techron and drove "aggressively" on some twisty roads. Problem is now gone and has been for 6-8 months. So, get out there and slosh that fuel around! I really think that helps a lot!