Re: spark knock problem
 

Tom
I really don't thing you need to recal or even worry about TPS, MAP deltas, AE, INT or BLMs just yet. I'd stick to the basics. The LT5 flat out does not do this is running properly.
Clear the codes and get it to do it again then see if any are set. If you're getting a lean o rich condition follow the trouble charts. They are meant for this. I had a sticking injector that set a lean code. The symptom was much like what you're describing. I put RC injectors in and the problem went away. That was 11 yrs ago.

Re: spark knock problem
 

Scott, thanks for the insights. I have RC injectors as my OE ones quite back in 05. I may have time this weekend to do the flow charts that are listed in the "Intermittents" section under Detonation/Spark Knock. Just to be clear, it's not setting a DTC when the knock happens, it's not even giving me a "winking" SES light.

I bought some SeaFoam to add to the gas....just as a look see as I can't figure out what harm that could do in a dilute form. I'm rather embarrassed to say that my car may not be properly driven enough and I have allowed too much carbon to be built up?:o

:cheers:
Tom

Re: spark knock problem
 

tom,

You shouldn't expect a DTC because of knock.

Re: spark knock problem
 

Tom,

I chased a very similar problem - light pinging between 1800 - 2200 rpm under light load - for years. Tried evrything including a whole can of GM engine topend decarbonizing spray, BG K44, new coils, new plugs, new map sensor, new knock sensor, etc...
In the end it turned out to be injectors.
I know you have a set of RC but components go bad sometimes.
How does the car run before fully warmed up? Does the symtom you are experiencing occur during cold temp operation?

Re: spark knock problem
 

Just a point of reference, AMSL for Chicago & most of the surrounding area is 600 feet - but the 93 octane is commonly available- even higher near the drag strip. So, if knock with 91 was present in your case, the altitude doesn't strike me as a contributor- might just be the octane?? (Cam timing comes to mind as well...)

No point, just musing out loud! ;)

Re: spark knock problem
 

Yes Dom, I understand that point. I just intend to verify that my ESC system is working correctly by using the flow charts for DTC 43 & 42 and the suggested steps in the Detonation /Knock section in the Intermittent troubleshooting guide section. I figure if I verify circuit integrity and component functionality then at least I can put the ESC module & knock sensor & fuel pumps to bed and move on to something else....I just don't know what specifically, but I think the mechanical due diligence should be run to the end of the charts just to be sure, no?


Yun, I will bear your experience in mind. Since we pay handsomely for the RC's I would have to say I tend to think "It can't be the injectors"....however when I drive the car with my scan tool connected I shall observe the fuel numbers also maybe I will see something. I just hate to assume it's the injectors out of hand. As to how she runs when not quite up to temp, I don't know for sure. I would have to say that I do believe that I don't notice any knocking when she is cool. I would have to say I will have to be way more rigorous in observing for knocks now that I seem to want to chase this down. Even if she's hot you need cockpit silence, windows down, and something for the knock to reflect off of to hear it. Even then it's sometimes very feint although I'm sure that's where my scanner will help me. I hope.

:cheers:
Tom

Re: spark knock problem
 

I know what you are saying, but it is very expensive and inconvenient to change the octane ($8 100oct unleaded is available in the Rancho Santa Fe gas station to service the big money toys out there), but it was easier to just drop a degree or two of timing in certain load cells.

I had already seen a wideband at wot and have new Lucas injectors, so I didn't suspect mechanical issues, just simply octane/engine load mismatch.

I could try to go richer, but I feel like that is a brute force tune (although I'd like to try it if I ever get a good deal on some dyno time- but I'll probably hold off for the day I get headers or something). I'm trying to make the engine and catalysts last and we might only be talking a couple of hp under the curve here and there. It still feels fast and might even be quicker with no knock retard coming in (not to mention the smaller exhaust diameter might have picked up a little mid range tq).

Either way, the peak hp is about the same with two different chips I ran.

Re: spark knock problem
 

I know this is an old thread, but since I came to a successful resolution of the "knock" issue I figured it may help some one in the future. (That's why I'm wasting server space putting it up. If the mods feel it's a waste of space just file this post in the circular file. :o)

Okay, so there is no way around the conclusion that the cause of the knock was me, or my inattention to detail. The knock came about because the spark plugs were loose....not finger tight loose, but loose enough so that one light application of force with the 3/8" ratchet and spin them out by hand loose. This conclusion is hindsight as some one from the brain trust we have here may have a better explanation. I put new plugs in and I have no "knock" any longer. To me the simple answer is as I said....I should pay attention better & don't let the plugs get loose!:o

The last plug change I did was two yrs ago. I use 41-602's with a light coat of motor oil on them as that's what was there from the factory. No anti-seize was on the FR2LS plugs that were in my car when I got the car. I never got around to doing a plug change this season so I never even checked the plugs for tightness and I do use a T/Q wrench when I change plugs. It's a beam/pointer type so okay I'm going to buy a new digital one some day. But I can't blame the wrench for my slackness!

Jut a fwiw, got some knock & no codes & good fuel PSI & no other stuff going wrong, check that the plugs are tight! Don't be like me & forget about them!:o

:cheers:
Tom

Re: spark knock problem
 

Tom Tom,
Just what I thought, not wrapped too tight...:)
Doug

Re: spark knock problem
 

Tom,

What do you torque the plugs to?