spark knock problem

[tomtom72]

I'm lost on this one guys and would be thankful for any advice.

When my 90 is all up to temp I get this spark knock during part throttle. It happens at part throttle with a moderate load like going up hills at less than 40 mph in 4th or 3rd. Sometimes I can even hear it on level ground at the same mph if I'm in 4th and give it small throttle input. I would like to add that this happens regardless the chip I use in the ECM. I have 3: AUAH, AYBK, and Marc's generic mail order piggyback.

I am not getting any DTC's, let alone the ones that signal a knock sensor problem. It has done this as long as I have owned the car. It seems to me the hotter the air temp gets, the worse this knock gets. Above 80* air temp is when, cooler air and it doesn't seem to do it...but I don't know if that is related to anything?

I used to put it down to the odd bad dose of fuel, but I try to stick to the name brands from stations that I know to move volume.

I have a new knock sensor that I was going to put in, but I was thinking what do I do if that doesn't address this issue? I was thinking that I could hook up the scanner and drive around and when the knock happens give a glance to see if it gives me anything to go on? I'm not real sure what to look for, knock events or what? My scanner has a line items "Knock Counts" and "Knock Retard".....is that what I should be looking at? TIA:o

:cheers:
Tom

I just want to state something so that there is no doubt about Marc's piggy-back thing. My car has done this since I bought it, AUAH or AYBK not withstanding. I just got a really bad load of gas last week and it kind of brought this to a head for me. The bad gas is gone and the knock is back to it's normal symptoms which the car had before I bought Marc's "chip" thing. I don't want anyone seeing this and connecting the knock issue to Marc's chip.

[Aurora40]

Hey Tom, those are exactly what you should look for. When there are knock events, the "Knock Counts" should increment. This should also trigger knock retard, and the timing advance will be decreased.

In addition to the knock sensor on a '90, there is a piece of circuitry that filters the sensor events and turns them into feedback to the ECM. It's on the passenger side of the engine bay, a sort of flat square piece. I can't think of the name of it at the moment.

I believe the car tests the knock sensor by intentionally advancing the timing until knock should happen, then checking to see if it gets feedback.

[XfireZ51]

Tom,

The calibration has modifiers for IAT etc. Those richen or enlean the base fueling depending on environmental conditions. You are hearing it but I"ll bet there's knock prior to the point of it being audible. If its there at tip-in, the Acceleration Enrichment can be both for TPS and MAP deltas. The AE is the pump shot adding fuel and allowing the INT and BLMs to catch-up. It gets decayed out when everything stabilizes. If you have a scantool, can you datalog? I'd want to see what's happening to the BLMs and INT when you go to accelerate or when you go up a modest incline.
Also, pull the plugs and see if there is any indication of detonation. Depending on what plugs look like, you may want to try a colder one.
I'm assuming FP is fine and filter is clear. Is motor stock?

[tomtom72]

http://i215.photobucket.com/albums/cc123/tomZR1/6-7-11%20Newtown%20CT/TuesniteinNewtownCT016.jpg

Thanks Bob for chiming in! In this photo, over by the washer reservoir cap, is that the box you're referencing? I think that is the ESC electronic spark control module...I fairly sure.

[mike100]

I took a little timing out of my Haibeck calibration right around 3800-4500 rpm in the middle Kpa map ranges. I used the tuner pro smoothing function to ramp the values. I left the 2000 and under range completely stock VE and spark etc for emissions testing and catalyst lifespan. I also cut back on AE in that range as well.

It still makes power at full throttle past 5000 rpm, just the 91 octane and 90 deg weather at dead sea level didn't work with the generic tune (not knocking Haibeck at all- pun intended), but nobody can possibly tune for all elevations and fuel blends across the country. The off-the-shelf tune did work well in Phoenix (1100 ft elevation) in 90 deg spring time temps- go figure- I think the LT5 is Kpa/ map sensitive, especially since 92 octane was the norm 20 years ago.

[tomtom72]

I knew I should have gotten around to learning this stuff sooner! :neutral:

Dom, I will have to go look at the manual for my scan tool and I'll report back. I have no idea because I have never been this deep into it's usage beyond doing a closed loop scan at idle :o.....I know, I know, then why have a scan tool...I'm a bit slow on the uptake because I don't play well with software.:o

The motor is bone stock. I didn't change the plugs this year, but in the past yrs I generally do so every spring in prep for my emissions inspection. I have never seen anything on the plugs. I have a picture chart for reference use, and my plugs are almost like new at every change. I can take pictures of past plugs & post'em....but I swear there is no fouling, no heat discoloration, no metal pitting or/and transfer & no insulator erosion or pitting....although this set in there now will have been in service for about 8 or 9 thousand miles by now and I shall pull them & look. The fuel filter is in service for two yrs now. The pumps tested okay last year, but I'll run a test now to lock that down.

Thank you Gentlemen, Bob and Dom, for help!:thumbsup:

:cheers:
Tom
Forgot this, I use delco 41-602's gapped at .035

[Kevin]

could be tip in knock, but i'm not sure

[tomtom72]

I took a little timing out of my Haibeck calibration right around 3800-4500 rpm in the middle Kpa map ranges. I used the tuner pro smoothing function to ramp the values. I left the 2000 and under range completely stock VE and spark etc for emissions testing and catalyst lifespan. I also cut back on AE in that range as well.

It still makes power at full throttle past 5000 rpm, just the 91 octane and 90 deg weather at dead sea level didn't work with the generic tune (not knocking Haibeck at all- pun intended), but nobody can possibly tune for all elevations and fuel blends across the country. The off-the-shelf tune did work well in Phoenix (1100 ft elevation) in 90 deg spring time temps- go figure- I think the LT5 is Kpa/ map sensitive, especially since 92 octane was the norm 20 years ago.

Mike, thank you also for sharing your knowledge!
:o I should say that to be honest, when you and Dom start speaking in "tongues" ( read that as ECM speak! ) I struggle to understand most of what you are saying. I left cars & went to boats in the late 70's just about the time electronic carbs came in so to say that I'm behind the curve is not accurate....it's more like I can't even see the curve from where I'm standing. :redface:

[XfireZ51]

I took a little timing out of my Haibeck calibration right around 3800-4500 rpm in the middle Kpa map ranges. I used the tuner pro smoothing function to ramp the values. I left the 2000 and under range completely stock VE and spark etc for emissions testing and catalyst lifespan. I also cut back on AE in that range as well.

It still makes power at full throttle past 5000 rpm, just the 91 octane and 90 deg weather at dead sea level didn't work with the generic tune (not knocking Haibeck at all- pun intended), but nobody can possibly tune for all elevations and fuel blends across the country. The off-the-shelf tune did work well in Phoenix (1100 ft elevation) in 90 deg spring time temps- go figure- I think the LT5 is Kpa/ map sensitive, especially since 92 octane was the norm 20 years ago.

Mike,

R U saying you cut back AE on the <2K range or in the 3800-4500rpm range?
The LT-5 uses a Speed Density system, so I guess it is MAP sensitive. The calibration you had may have been fatter in the higher kPa range since the motor would be operating there more often in Phoenix. Drier air too. Moving to SoCal, the VE could have been a bit lean in the lower VE range.

[mike100]

Mike,

R U saying you cut back AE on the <2K range or in the 3800-4500rpm range?
The LT-5 uses a Speed Density system, so I guess it is MAP sensitive. The calibration you had may have been fatter in the higher kPa range since the motor would be operating there more often in Phoenix. Drier air too. Moving to SoCal, the VE could have been a bit lean in the lower VE range.

yeah, I cut back or totally zero'd AE in the range which I believe the CA state inspection system runs their IM-240 equivalent (4 minute dyno test- really it's about a minute nowadays). That's all below 2000 rpm mostly at light loads. This also tends to keep the mixture leaner during light cruise which should help with economy and Cat lifespan.

Then I reduced/smoothed out the timing in the range it pinged and where I believe the load points to be KPa wise. I didn't take a lot out

the only mods I have done since was to go to a 2.5" Corsa from a 3" B&B I traded and it 0-60's ever so slightly quicker, but I haven't re-dyno'ed it or anything. I doubt it would be leaner- but that's really a guess.

I will probably be buying an emulator gizmo soon because I want to datalog or at least hit trace a few maps just to be sure where it really operates in certain modes.

[scottfab]

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.

[tomtom72]

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

[XfireZ51]

tom,

You shouldn't expect a DTC because of knock.

[secondchance]

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?

[Paul Workman]

I took a little timing out of my Haibeck calibration right around 3800-4500 rpm in the middle Kpa map ranges. I used the tuner pro smoothing function to ramp the values. I left the 2000 and under range completely stock VE and spark etc for emissions testing and catalyst lifespan. I also cut back on AE in that range as well.

It still makes power at full throttle past 5000 rpm, just the 91 octane and 90 deg weather at dead sea level didn't work with the generic tune (not knocking Haibeck at all- pun intended), but nobody can possibly tune for all elevations and fuel blends across the country. The off-the-shelf tune did work well in Phoenix (1100 ft elevation) in 90 deg spring time temps- go figure- I think the LT5 is Kpa/ map sensitive, especially since 92 octane was the norm 20 years ago.

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! ;)

[tomtom72]

tom,

You shouldn't expect a DTC because of knock.

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

[mike100]

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! ;)

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.

[tomtom72]

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

[Mystic ZR-1]

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

[XfireZ51]

Tom,

What do you torque the plugs to?

[tomtom72]

Tom,

What do you torque the plugs to?

Dom, I use the T/Q spec in the FSM. If memory serves me, and usually that's not the case as I look it up before I do the change. I think it's around 19 Nms or maybe 22 Nms.

This is my first aluminum motored car so I will admit to a larger percentage of error on my part. Putting plugs in an iron head vs an aluminum head the 'feel' of the threads to me is different when bringing the T/Q to spec. I know that is preposterous, but to me the 'feel' is different in your hand from the wrench.
:o

Anyway, all's well now and I'm back in 'love' with my girl! She ran very well on Sunday. :sign10:

:cheers:
Tom

[tomtom72]

I'll tell you this much Cliff, the car ran so bad past say 4k that I was thinking that I had really big problems. It was just terrible to hear! Strange as this seems the plugs that I took out showed no signs of anything wrong. The electrodes and center insulator were intact, no pits or anything amiss. They were a uniform medium brown color shaded on one side. I will post pictures if it would be of use?

To look at the old plugs you would say maybe the fuel was a wee bit fat, maybe as my plugs usually on an annual change schedule look about what new plugs look like.

I also say this much too. I'm fairly sure I will never get the hang of using antiseize. I used to check the plugs at random intervals and I would find them a bit loose. It was annoying. That's why I switched to what was on the OEM plugs, just a light coat of oil. I got better results with the oil for getting them not to be loose. I suspect that I will buy one of those new T/Q digital wrenches for future use. I have this fear of pulling the threads as the feel to me is so different than tightening the plugs in an iron head. I know, I'm just nucking futs!

:cheers:
Tom