At what point can you here detonation?

[Jas89TTA]

On my scanmaster it's picking up KR as high as 40 I'm pretty sure it's false knock but was wondering at what point will you here the detonation (pinging) from the motor? The high numbers just started today, but it was picking up KR from 1-14 deg a few days ago but I've never heard the pinging sound. I belive I have tranny issues and was wondering if it could this problem of false knock? My trans does not shift they way it use too and I noticed that the converter does not seem to stall like it did in the past. It's a 3500 stall and I would have to push the pedal down aways to get the car moving, now I just touch the pedal and it accelerates.

 

[Lee_Burough]

Free Advice....

You'd better treat a reading of 40 degrees of Knock Retard as real!!!

If it is real, you've already damaged your engine!!

Turn down the boost and start eliminating the causes of mechanical knock, then move on to tuning issues....Do that at 10 PSI until you're sure

False Detonation

As stated above, False Detonation is a noise that falls within the bandpass frequency of actual detonation or abnormal combustion and causes the ECM to remove timing just as it would in the normal course of events.

This is very bad as it severely limits power as timing is removed. Sometimes, false detonation is fairly obvious as it occurs at launch, or on the one-two shift and quickly subsides. Other times it is not so obvious as it may occur more continuously and it can be difficult to identify.



I think the most common causes of false detonation occur from wheel hop, or, the downpipe contacting the passenger side rear of the upper control arm when a bad engine mount on the driver's side allows the engine to rotate too much.

Rear wheel hop is more a problem at launch in low gear while the downpipe hitting the control arm often occurs on the shift point.

Other known causes are such things as the exhaust hitting the bottom of the firewall, crossover pipe banging the manifold on the passenger side, a loose exhaust pipe at the rear hanger off the tranny mount, a noisy valve train, loose torque converter, loose converter inspection cover, rattling lines from the tranny to the radiator, a missing bolt in the AC compressor, bad idler pulley bearing, loose innercooler bracket, and/or a too tight engine hold down strap. Piston slap on a cold engine with excessive clearance has been reported and such things as a bent push rod will also trigger the detonation sensor.

If the detonation sensor is over tightened, it may become too sensitive. Factory torque setting is 14 lbs-ft....just barely more than finger tight. Make sure someone has not cranked it in excessively.

 

[Lee_Burough]

Go HERE for some good reading, maybe it will give you some good ideas.

 

[Jas89TTA]

Sorry, I forgot to mention the 40 KR was with less than 10 PSI of boost as was all the KR readings thats why I figured it was false and also never did here any pinging. Thanks, For the link.

 

[Lee_Burough]

That is good news! Its prolly something simple. The only time I've heard pinging myself was with bad gas.

Attached a picture of my engine tie down....May be a good place to start if you don't have one already. Have somebody watch your engine as you brake torque. A couple inches of engine movement is too much with our small clearances.

lee

 

[zerotta]

Just wondering if here = hear in this thread?

 

[bruce]

On my scanmaster it's picking up KR as high as 40 I'm pretty sure it's false knock but was wondering at what point will you here the detonation (pinging) from the motor? The high numbers just started today, but it was picking up KR from 1-14 deg a few days ago but I've never heard the pinging sound. I belive I have tranny issues and was wondering if it could this problem of false knock? My trans does not shift they way it use too and I noticed that the converter does not seem to stall like it did in the past. It's a 3500 stall and I would have to push the pedal down aways to get the car moving, now I just touch the pedal and it accelerates.

Typically, the chip can pull out as much as 12d of timing when it is told detonation is present. Detonation doesn't have a min db level. And in the case of preignition, can be silent.

Without a complete investigation, you don't know that it's *false knock*. Jumping to the conclusion that it's false, when in fact it's real, can be very expensive.

 

[83ttypecooled]

Hi,
In the case of my Regal, pinging has been the norm. I thought I had it fixed when I found that my fuel pressure had been dropping down to twenty while on it, so I replaced the pump with a Walbro 340. No luck, still pinged, though it didn't misfire anymore. I tried a bunch of other stuff, to no avail. In short, I haven't been able to fix the problem.The detonation has gotten so bad, it blew the electrodes off of plugs 3 and 6.At this point, I am gonna pull the heads and see if there is something obvious in there. I'll let you guys know....

 

[Lee_Burough]

Hi,
In the case of my Regal, pinging has been the norm. I thought I had it fixed when I found that my fuel pressure had been dropping down to twenty while on it, so I replaced the pump with a Walbro 340. No luck, still pinged, though it didn't misfire anymore. I tried a bunch of other stuff, to no avail. In short, I haven't been able to fix the problem.The detonation has gotten so bad, it blew the electrodes off of plugs 3 and 6.At this point, I am gonna pull the heads and see if there is something obvious in there. I'll let you guys know....

Before you do that, try something easy....Clean the combustion chamber to rid it of carbon deposits. Carbon build up glows red hot and will detonate your fuel charge on contact. GM makes a spray you put into the intake to clean carbon deposits (Top Engine Cleaner #1052626). Follow instructions and it could save you a lot of unnecessary work. Chevron Techron fuel system cleaner (not fuel injector cleaner) could help too.

HTH

lee

 

[89ICBM]

[Jas89TTA] On my scanmaster it's picking up KR as high as 40 I'm pretty sure it's false knock


OK, I'm gonna go out on a limb here, if you had detonation bad enough to cause the ecm to pull 40° of timing, you would have heard it and it wouldn't be a ping, it would sound like gravel running through your intake. Check your ignition module and coil pack. Pull them both and seperate the 2. If the module is all scammer, kinda like undried glue, there's your problem. I've had tranny issues before and never had them effect knock retard but, with these cars, anything is possible.

 

[Razor]

If the knock readings come up and stay.. then its metallic noise. If they pop up and then disappear.. its false.

I had a broken tensioner on my timing chain cuase me 3 months worth of grief.

Cam could be wiped, chain could be stretched, torque converter could be coming apart, belt tensioner could have a bad bearing, MAF pipe hitting the engine, etc..

IF you have a scanmaster and are seeing the knock on it, when you start depressing the gas and the car goes into power enrichment, look for the O2's to be in the 840-860's.. this will indicate you have plenty of fuel.

Inspect plugs for any signs of issues. All cylinders should look the same tan'ish color.

Make sure all the readings on the scanmaster are normal at idle. Example, BL's in the +-10 from 128

Reality.. its a go down the list of possibilities.