hey guys ? did some datalogging and was getting some knock counts, if i get real knock counts should i see the timing retard, will roller rockers give false counts thanks geo.

what engine? I have heard that rollers can cause this.

sorry bogus 1990 corvette L98 1.6 roller rockers

Good question, I was going to ask this myself. I heard a lot of LT1 guys swap in a LT4 KM. Can you do that on a 92?

Yes, the knock module is located on the bottom side of the PC board of the PCM on the LT1/4 cars. I just ordered an LT4 knock module for my ongoing project.

Additionally, I have read that you can desensitize your knock sensors by using teflon tape on the threads. This could be bad though, in the event you might get some real detonation going on somehow.

Have you had any problems with your 383 in regards to retarded timing due to knock? Just wondering, because I ordered the LT4 module just for insurance since it was listed as a supporting mod for the top-end engine work I'm doing.

You might want to read this thread over at Brand X:

Why does the LT4 knock module work WORSE than the LT1 KM?

Quote:
No
Quote:
No its not, that is 94-96 only. 92 and 93 use a different ECM.

Well damn :sad7:

What do I do now? lol

Quote:

Case - thanks for correcting me. I made a bad assumption that the earlier 92-93 had the same ECM

No mate, the 94-96 have a PCM, its substantially better than the 92-93 ECM. Can be programed an unlimited amount of times via the ALDL connection, can control a 4L60-E transmission, and can allow varied injector pulse width for each injector to potentially allow alot better tune, that and many other little improvements.

ok back to my prob. if the knock sensor on a 90 L98 detects a knock should you see timing retard if your are datalogging, I saw the knock count around 14 but never saw where ecm retarded timing, so i am thinking its my roller rockers that sensor is picking up what everyones thought thanks geo.

geogolf

The following is advice on an '85 to '89. I do not know what setup your '90 is or if the following mod will work for you or not. If not, it is still good information for others so I figured I'd post it here. I am personally going to do this mod before I run my new combo this year.




Tech Tips >> C4 Related Tech Tips >> Upgrade your
'85-'89 ECS module.
Tech Tip

Upgrade your '85-'89 ECS module. -- 1 of 1
Date Published: 2001-09-09

Submitter's Name: James Kovitch
Email Address: jgkov@msn.com
Corvetteforum.com Member Alias: 65Z01

Background The '85-'89 L98 uses an Electronic
Spark Control (ECS) module to listen to the Knock
Sensor and report ping to the ECM (on '90-'96
Corvette motors the ECM listenes directly to the
Knock Sensor). When the ECM detects knock counts
it pulls timing till no knock is reported and then
gradually increases timing to the current
setpoint. Problem Even with base timing at +6deg
and running the stock MemCal chip, my '88 L98 was
plagued with false knock counts under WOT
operation (seen on my AutoXray scan tool). These
were causing timing to be pulled, which I felt was
hurting 1/4mi performance. Solution When I
discussed this issue with Gordon Kilebrew, at
Corvettes at Carlisle 2001, he told me to replace
my stock ECS module with the upgraded unit: GM P/N
16038331 (AC Delco P/N 216-35). Verification After doing this upgrade a
short WOT run on the highway showed no knock
counts on my AutoXray. Subsequent testing at the
local drag strip showed an improvement in trap
speed of about 1 mph. No other changes had been
made and trap speed data was normalized for
weather conditions to provide a valid comparison
with prior time slip data. Equipment Safety This
upgrade is safe for the motor since the ECM checks
the ECS module occasionally by advancing timing
till a knock count is registered; if no knock, the
ECM would record a code 43. Just to be sure all
was well, I advanced my base timing to about
+12deg and made a WOT run on the highway; 7 knock
counts had registered on my AutoXray.

dan mine is a stock 1990 ecm so i think it gets info from the knock sensor directly ,like i said i was seeing knock counts but was not seeing my timing retard, so i am thinking it is a false knock caused by my roller rockers

Yeah, I wasn't sure how the '90 was set up. I do know that even false knock can cause the timing to retard, if it is severe enough, on any of our cars. Sounds like yours isn't that bad if it isn't retarding the timing.

Quote:Knock counts cause the computer to retard the timing. The ECM can't discriminate real detonation from falsely triggered knock counts. The knock counts are the same, regardless of the cause. Your timing should be being retarded if you are getting counts. Possibly you don't have your scanner set up properly or your prom has been reprogrammed to ignore knock counts, (if that is possible).

RACE ON!!!

Wow, I just saw your location is Brookville, PA. I spent all summer working between Brookville and Hazen. I was the superintendent on the Rt. 28 project going into Hazen. You must know the Lindemuths and their dirt track racing team.

dan yes i know them, do you work for ia or hawbaker i used to haul asphalt for Hri then ia bought them out, now i am semiretired only work two days a week

cfi not using scanner have a laptop and tunerpro which is working fine, everything else shows up. so will have to search a little deeper

Quote:

I work for Hawbaker. The job I did ended right at Allens Mills Road if you are heading towards Hazen from Brookville. The company is actually getting ready to start construction on another piece of 28, just before going down into Brockway. I'm not doing that section tho, I'm already slated to start a 2 year job on 879 in Clearfield.

With the knock, again I'm not sure on your year of car, but I am pretty sure the computer doesn't pull timing for every knock count. I think you have to see a certain amount of knock before it starts pulling timing, and you might be under that limit. You could retard the timing back to near 0 or 2 degrees and see if you get fewer knock counts. If they stay about the same then it is false knock. If the counts go away then it it real knock. If it is false knock you could try removing the knock sensor and putting several wraps of teflon tape on the threads to see if that helps "deafen" it.

dan i am going to get a new sensor and try that, i doubt sensor has ever been replaced. maybe iwill see you at a vette show sometime, good luck in clearfield prob a little less drive geo.

(channeling CFI-EFI)

Make sure you're not just killing the messenger by replacing the sensor ...

j3 not sure i get your meaning. but whatever the problem it is not retarding timing so will change sensor and keep a eye on it thanks. geo.

What he is saying is, it doesnt appear to be an issue with the sensor, and i tend to agree.

In order of preference:

Have a good listen around your engine with a stethascope, around the heads, rocker covers, timing chain cover, and pulleys.

Then consider checking around your headers for leaks, ive heard small leaks between the header and the head make ticking noises.

Check the wiring to the knock sensor, and be sure its not going near any spark plug leads or anything else simular. Make sure your plug leads are not arcing to ground and causing a ticking noise. Check the plugs dont have cracked insulators, allowing them to arc to ground.

Consider doing a compresion test, but more so a leak down between adjacent cylinders. If there is a leak between 2 adjacent cylinders, this could create a ticking noise or minor knock.

CFI-EFI and TopTechx6 will probably be able to give some other very good examples of where you may want to look for a false knock (if indeed that is what it is) There is a hell of alot of knowledge and experience between the two of them.

Some of those may sound like a way out there last ditch test, but its better to try them before you go and start wasting money of parts that may not help (i havent read every post here yet, but i just dont feel youve done enough diagnostic testing to go ahead and replace a part, and im having trouble finding enough evidence here to suggest youre looking at the right part to replace). If the parts dont help and you get stuck for ideas, youre then up for the cost of someone else doing the diagnostics.

Quote:That doesn't quite apply, here. There is no code and therefore no messenger. But the caveat still applies. The knock sensor is working. You have detected knock counts that proves it is working. It is a waste of money to replace it. If anything, the old knock sensor may have lost some of its sensitivity over the years. A new knock sensor can only make matters worse, besides wasting of money.

If you are sure it isn't retarding the timing, then apparently there are insufficient knock counts to trigger the ECM into retarding the timing. In that case, there IS no problem. You are trying to fix a nonexistent problem. If you want to test your ESC, try advancing the timing to increase the knock counts, and check to see if the timing gets retarded. If it doesn't, there is a problem somewhere else. Unless you can't increase the knock counts by inducing real knock, you have evidence that the knock sensor is working.

RACE ON!!!

(sorry to call you stupid CFI, but I don't see an "I agree" smiley.) I am 99% sure your knock sensor is fine as it is sending it's message to the ecm, and you are seeing it. I would first, as I mentioned above, retard the timing and repeat the driving test you did before to see if the knock showing up is less or the same. If it is less or eliminated then you have real knock. If it is about the same reading, do what CFI said. Advance the timing to induce knock, then watch for the automatic timing retard to happen. If it doesn't then something isn't working right. If it does, then all is fine and again it is probably false knock. Case gave you many good places to look for it once you determine if your knock is false or real. Also, roller rockers and headers and such can give you false knock counts that can't be eliminated, so the teflon tape on the sensor can help to make the sensor less sensitive, just don't overdo it and compeletly deafen the sensor, and don't do that till you are 100% sure it is false knock you are getting.

As a side note, if you do end up finding that you think you have a bad knock sensor (like I said I don't think you do), I have a brand new never installed knock sensor for an '89. If it will work in your '90 (I'm not sure, you would have to check it out) and you determine yours is bad I can ship it to you to try, then you can either replace it by buying me one or just ship mine back to me after you decide if it fixed your problem or not.

thanks dan cfi is prob. on the right track, i am not seeing to many counts most i saw was 14 so might not be enought to trigger timing, but thanks everyone for your help. will wait till i can get car out and run it a while then check again hope for a short winter geo.

As a follow up, when I found knock counts in my car, I drained my 85 octane gasoline and filled up with 91. Then I set my base timing to zero. I was still getting knock counts, just revving it in neutral. That convinced me that my knock was false. I promptly disconnected the knock sensor at the ESC plug. Now, after 1/4 mile testing, I have my base timing set at 14° BTDC and I get no knocking.

RACE ON!!!