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Old 06-27-2017, 08:17 PM   #1
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94 Z28 Camaro High rpm knocking Huge Adv Retard Knock

Alright so I am back this will be long so bare with me I have been threw alot with my car i will most likely put a forum of building my car as i need to update my sig
The story of the car and engine:
I no longer have my red car well i do but its a long story for another forum, but to get the short story I had a drunk kid who lived around my block who totaled my girl at 3 in the morning while she was parked outside my house the frame was ruined could no no longer drive the car straight i work at a body and paint shop trust me it was irreversible he hit my car at 40mph plus he said anyways so everything in my sig is still accurate i took out the engine of my car bought another 1994 camaro Z28 that was blue that didnt run except i got it too run by changing the optispark because we all know thats usually what it is haha anyways so after my car was totaled I got the second blue camaro took out the automatic lt1 even tho i got it running because i wanted a manual car which my car that was totaled with the engine im running now is still my lt1 m6 1994 also **Im still running my original m6 lt1 engine from my old red car just put it into the new body so now i have the automatic lt1 in my garage for when my m6 lt1 goes or just to build on it while im running my m6 lt1. Alright so after the engine drop in i took it to my paint shop. I now have my 94 Z28 Camaro with Kandy Brandy Wine Paint with flake and 2016 Z06 Corvette replica rims Car is really nice now but thats not the point of this thread.

Issues with the motor leading up to this point:
So after the motor drop this happened during school and i turned a shell camaro with a non running engine into the car i have today in 2 months because i wanted to have it done before school ended which i did just recently I was doing tune up work on my engine checking things noticed that number 6 spark plug wire was burned fully threw no way was there spark, I drove my car like this with 7 cylinders i would say for a solid month because i didnt no, and no i didn't feel loss of power nor did the car sound weird to me. Ok so once i found this problem I stopped driving my car and ordered the custom length OTVC MSD 8.5 mm wires and replaced the spark plugs because the spark plug that had no connector on it was definitely shot when i pulled it it was the only spark plug that was fully black and you could tell is wasn't firing for a long time. After i was done with the installation the car fired right up perfect but when i drive any acceleration you can just feel the car like it feels bad to the motor to accelerate its tumbles and has no power WOT makes no difference and Im honestly afraid to go WOT because of the way light acceleration feels its thats bad Im confused because my car ran way better when it was only on 7 cylinders ran perfect but now i cant even go down the block without it backfiring and stumbling i could most likely drive the car anywhere i would have to be really light on the throttle and it would take a long time to get to highway speed starts fine idle is a little weird sounds like its missing at idle too anyways sorry for the long post here is the log file
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File Type: csv DLOG-Save-2017Jun27-173446-2G1FP22P1R2192304.csv (354.5 KB, 7 views)
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Old 06-28-2017, 09:37 AM   #2
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Re: 94 Z28 Camaro High rpm knocking Huge Adv Retard Knock

Maybe, just maybe if you replaced all of the wires you have a couple of them on the wrong location on the Optispark Distributor. Just take your time and do a double check to make sure, if you haven't already done this. It wouldn't be the first time somebody accidentally did this.

And, check the wire routing again. Did the new wires end up against the manifolds and get burnt again ?

Do a double check, and make sure they are all secured at the Optispark Distributor and at the Spark Plugs.

Last edited by gaedbo; 06-28-2017 at 09:41 AM.
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Old 06-28-2017, 04:48 PM   #3
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Re: 94 Z28 Camaro High rpm knocking Huge Adv Retard Knock

Yes that is what I was thinking to just checked today sadly they were fine.
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Old 06-29-2017, 03:53 PM   #4
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Re: 94 Z28 Camaro High rpm knocking Huge Adv Retard Knock

Bank 2 (passenger side) is pouring in a huge amount of extra fuel to prevent it from running lean. Cell 16 (idle) is 137 Left/160 Right for LT's and 127/141 for ST's. The resulting multipliers mean the right side is adding 38% EXTRA fuel, compared to what the PCM thinks it should need. Left side is adding only 7% EXTRA. For most of the other cells, the passenger side LTFT's are close to being maxed out at 160. Driver's side are close to 128. Definitely a passenger bank problem.

Knock retard accompanies any significant movement of the throttle. From fractional degree to 5+ degrees retard. Could be the possible lean condition on the right bank. Misfires can cause the PCM to add extra fuel, and that can cause it to actually run rich (not "huge" - can range up to 15-deg, just frequent). Best thing to do is inspect a couple passenger side plugs, and compare to a drivers side plug for signs of a rich or lean condition on the passenger side.

The engine is on not excessively warm side at 200-degF with one fan running all the time (?? - program change?), and intake air is running hot at 122-126-degF, which can contribute to knock. Periods of max knock retards coincide with the high IAT.
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Old 07-12-2017, 03:51 AM   #5
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Re: 94 Z28 Camaro High rpm knocking Huge Adv Retard Knock

I have always seemed to have issues with blms and the car running rich on my car but it had never made the car knock or have no acceleration. I just recently extended the harnesses containing the O2 wires ABS plug wires starter, ground and knock sensor wires to move them away from the header and closer to the accessory bracket I heat shrunk and soldered everything but, I DID NOT solder anything to the o2 wires i had to use two 02 extensions due to fear of reading past problems with the soldering of 02 wires so could the 2 extensions on the passenger side vs no extension for the driver side throw the blms off that much? The o2 sensors themselves are in the same place relative to each other and same distance from engine

Checked plugs passenger side definitely seems to be running more rich then driver side.

Hmm yes I have done quite a few program changes to the car trying to get better gas mileage Ive always had bad gas mileage most recently i came across this site.
Free Online Tuning Service ? fbodytech
Its where i got my definition file for tuner cat anyways i used the free online tuning software to try to attempt to get better gas mileage i checked the option to have fans temps lowered i guess it lowers them a bit too much because your right i have notice the fan is excessively on.

Im not sure whats up with my IAT will look into it

So I decided to just replace the optispark with the one from my other lt1 and see if it fixed the problem and what would you know it did car no longer is missing light acceleration missing is gone can beat on the throttle now with no problems

The new log file right after a couple warm cycles to fill the coolant up. It seems my blms have cleared up better then before could this indicate an issue other then the optispark was fixed during the replacement?
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File Type: csv DLOG-Save-2017Jul10-200056-2G1FP22P1R2192304.csv (2.18 MB, 3 views)
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Old 07-12-2017, 10:23 AM   #6
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Re: 94 Z28 Camaro High rpm knocking Huge Adv Retard Knock

Downloaded the file and set it up. Work on it today if I can.
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Old 07-13-2017, 11:16 AM   #7
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Re: 94 Z28 Camaro High rpm knocking Huge Adv Retard Knock

Appears you have solved the LTFT problem, except at idle. Everything other than Cell 16 is within +/-3 of 128. Exceptional. Cell 16 is 140 Left/129 Right. Must still be some sort of small vacuum leak or small exhaust leak on the left side.

Only found three instances of knock retard. Two of them are insignificant, only a fraction of a degree. Seems to happen when you roll slowly into the throttle. Isn't affecting the engine's performance. One incident when you went 100% throttle, amounting to a max of 5.06-degrees retard. Check your advance tables above 4,000 RPM with MAP above 80 kPa. You are running about 40-degrees advance when the KR starts. See how that compares to the stock tables.

When you do enter power enrichment mode, to me the O2 readings look to be on the high side... not unusual with the stock tune. Recognizing that the narrow band O2 sensors are not particularly accurate at 900+ millivolts, its a somewhat subjective observation. But I would expect them to be closer to 900 mV for max power. Have you ever tweaked the target A/F ratio, using the PE mode tables? Stock PE tables usually produce a target A/F ratio of 11.7:1. Usually make better power/torque closer to 12.8 - 13.2:1.

Your IAT is a more reasonable 100-102-degF in this log.

And a disclaimer.... I am NOT a tuner. I can only base my observations on what I have seen in hundreds of data logs over the years.

Last edited by Injuneer; 07-15-2017 at 12:15 PM.
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Old 07-14-2017, 07:32 PM   #8
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Re: 94 Z28 Camaro High rpm knocking Huge Adv Retard Knock

That sounds great, I will check for leaks.

Are you saying that this knock could be do that my PE tables are modified?

No I have never modified any PE tables or AFR at least purposefully, Ive never understood it enough to trust my self to try to tune my car myself in that way. However from the site I listed I may have checked an option like improved throttle response or something else that may have tweaked the PE tables im not sure it was a while ago that i have loaded a tune and i tried many different tunes to try to fix my speedometer issue as i put the Corvette replica wheels on along with at fact that the rear end now has different gears than from when it was in my true m6 car right? I never did fix this issue with the speedometer just been dealing with it.

So during that time i was trying different options on the tuner site and i am not sure what options I winded up keeping so it is possible some tables could be tweaked.

I can reload a stock fresh tune to be sure nothing is modified then i can modify it to help fan temps egr delete vats etc ive done this before on the car but i would never try modify PE tables and other tables like that myself. And thank you for you advice and help this whole time.
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Old 07-15-2017, 09:54 AM   #9
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Re: 94 Z28 Camaro High rpm knocking Huge Adv Retard Knock

Sorry.... in the edit, I went back and added the sentences starting with "Stock PE tables...." to the wrong paragraph. Those two sentences should have been added to the next paragraph regarding running rich in PE mode. I'll correct that when I get back on my PC.
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Old 07-15-2017, 12:39 PM   #10
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Re: 94 Z28 Camaro High rpm knocking Huge Adv Retard Knock

Corrected post #7.

The paragraph on "knock" suggests that you may have aggressive timing in the tables. It doesn't appear to be due to running lean, since it appears to be running a bit rich in PE.. You are at an elevation where barometric pressure is only 88kPa. So it can't be a problem with compression ratio. At that elevation, the stock 10.5:1 produces combustion chamber pressure that is equivalent to 9.1:1 static compression ratio. On the other hand, what is the octane of the fuel you are running? Is that the max available in your location?

So that leaves too much timing, or a mechanical noise.

As far as timing, the auto tune program may have advanced it a bit. I have a partial spark table in my Scanmaster writeup, primarily as an illustration. It is only the portion of the table that extends up to 4,000 RPM. At 85 kPa and 4000 RPM, the table, which I believe is stock, shows 37-degrees. You are at about 40-degrees in the data log (advance + knock retard). Maybe the auto tune program doesn't reflect altitude adjustments?

The main part of the knock doesn't appear right away. Initially you get 1.31 degrees of knock retard, in response to an increase in knock count from 3261 to 3356. That appears to be a response to reaching 100% throttle. The retard starts to decay, until knock count again increases, from 3356 to 3570. That kicks the retard up to 5.06 degrees. Interestingly, that is at the exact moment you let up on the throttle, from 100% to 85%? Is it possible something is generating an impact noise, like a loose motor mount? The passenger side mount is right next to the knock sensor.

I would try pulling a bit of timing advance out of the tables. No more than 3 degrees initially.

As far as the PE tables, there are online guides on how to change them. This site has some interesting advice on tuning, and covers the PE tables in the "WOT" section.

LT1 PCM Tuning - Tips & Tricks for DIY Tuning!

And if you are going to be doing your own tuning, a wide-band O2 controller may be a wise investment.
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Old 07-15-2017, 03:16 PM   #11
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Re: 94 Z28 Camaro High rpm knocking Huge Adv Retard Knock

I had a knock retard problem with my Z28. Injuneer suggested that it may be noise generated, possibly with my exhaust system or motor mounts. I found that the threads on one of the exhaust pipe clamps was contacting the frame, and the sheet metal piece between the muffler and the gas tank was making contact. I corrected these 2 issues and the knock retard almost totally disappeared.
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Last edited by gaedbo; 07-15-2017 at 03:21 PM.
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Old 07-16-2017, 02:33 AM   #12
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Re: 94 Z28 Camaro High rpm knocking Huge Adv Retard Knock

Ok i will look into the site. Im running 87 octane where i live i believe 91 is the max my town has.

Well from both of your points i could definitely see my headers being a issue generating mechanical noise if one of the primary's are resting against the k member? I had clearance issues putting the headers in which had me shaving down part of the k member and having to use a oil filter relocation kit i believe there is still some primary tubes with very minimal to no clearance at all resting on the frame and or k member, could this generate it?
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Old 07-16-2017, 08:11 AM   #13
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Re: 94 Z28 Camaro High rpm knocking Huge Adv Retard Knock

Try running the 91 and see if the knock retard goes away. If it doesn't, that may make mechanical noise the primary suspect.
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