I have been dealing with an abnormal amount of detonation or pinging on my 1989 ZF6 L98 with 147k on the od. I've talked to a few members on this forum and they've given very helpful and thought out advice but so far nothing has worked.

Here's my situation: at any more that 1/4 throttle i get extreme pinging, it occurs at all rpms and temperatures (unless the car is really really cold). The pinging is a little better if the car is cooler than 190 ish. I also have a Code 32 (egr).

I have tried:
Higher octane fuel (93)
Octane booster
Fuel system cleaner (detergent based)
Checking knock sensor torque (14 ft/lbs)
Unplugging knock sensor (suggested by members to force a set spark advance)

So far nothing has effected the severity of the detonation. I have an aftermarket knock sensor and am working on getting a oem sensor.

I made a list off all the thing that I've read can cause detonation:

Egr
Egr solenoid
Egr temp sensor
Egr vacuum leak
Pcv valve
Carbon build up
Fuel filter
Fuel pump
Clogged injectors
Bad/off timing
Bad/inaccurate knock sensor
Ignition control module
Bad ecu
Too low octane
Mechanically advanced timing

My pcv valves do seep oil (is that a sign that they are possibly clogged or stuck open?). I do have an egr code. My knock sensor isn't oem which could cause it to be inaccurate. I don't know when the last time the fuel filter was changed. Ive almost always run premium (91 or higher octane). I'm really not sure where to go from here. A final detail that ive always ignored since its been happening since i got the car 7 months ago was it takes a while to crank up in the morning, but fires right up if its been run recently. Not sure if that could be related either.I have tools, I just don't know where to start. Any ideas would help.

My airbox is cut with a k&n filter, i have a gutted cat, and flowmaster 40 mufflers. The detonation was not occurring when these mods were new.

Sorry for the longer post im just trying to give as much information as possbile because i need my trusty (or maybe not so much) c4. Its my only form of transportation besides feet.

 

I would say its probably fuel or timing being bad, not going to be EGR. Do you have a scan tool or cable to connect to your laptop? It should be showing knock counts in real time.

Verify the timing, 6* BTDC is the base. Check Fuel Pressure, should be about 43-45psi. Pull the plugs and look at them, is one side abnormal? Wet? burnt white?

 

Sorry, didnt read it all but are you sure it is pinging? when my FPR went out, it ran like crap - but would run.

 

Which cable would i need to connect my laptop to the the car? Is there an app i need too? I thought the timing could be off too but I've never touched it before. Can it somehow untime itself? I will verify regardless. I will pull plugs and check fuel pressure aswell.

it sounds like this:
It still runs/idles fine. I drove from Northern Nevada to Southern Arizona (VERY carefully) with this happening luckily it still is fine below quarter throttle so i could avoid pinging. It hurt but i had no choice.

 

From the driver seat, pinging will sound like a rapid fire of little bells going off.

Are you noticing a loss of power when the supposed pinging is occurring?

In your other thread on this subject it was recommended to check your spark timing. Have you done that?

Also, check it with a dial back timing light so you can verify it at higher engine speeds besides idle. Checking it your driveway.... It'll all be a very low engine load, but you can still verify you're getting correct timing. For example, I'm looking at the spark map calibration on a Vette of your model year, at 2500 rpm and low engine load you should be getting ~47° BTDC.

The ignition control module has a role to play in the ECM determining ignition timing. Aftermarket modules can actually produce a different amount of timing than the factory one. For example, my Petronix module was causing the ECM to command 5° less than the factory module (which I found out by using a dial back timing light in my driveway). Other aftermarket (performance or stock replacement) modules may induce more timing. This is independent of engine load, so it can be diagnosed in your driveway with the car in neutral.

Below is the spark map for a 89 Corvette. The circled area is about where you'd be if you're reving your engine up in your driveway. If you find you're getting well over 50°, then there's some issue with distributor commanding more timing than the ECM is telling it to.

Also, your spark plugs might have tell-tale signs of pinging... damaged electrode, salt & pepper appearance on the ceramic, etc...

 

Ive watched a bunch of videos and read a few descriptions of what detonation should sounds like (mostly in denial). But it's definitely detonationing. It sounds kinda like a bunch of pebbles hitting the firewall, or something rattling harshly, like the video above.

There is a lost of power, not as drastic as i would've exspected, but it's not running as well through 2000+ rpm

Not yet. I've never used a timing light and I've been on the road the past couple days driving/sleeping. Its on my list now that ive arrived. In the middle of moving so i don't have alot of tools or a place but im gonna find a good parking lot by an autoparts store and go through the list of ideas given to me.

Its in the low 110°s right now so I'll pull plugs tn once it cools down and try to get my hands on a timing light.

I hope you're right in your doubt of pinging. It would make my day What do you think it would be if it's not actually detonating?

Thanks

 

Well, I'm not saying that I doubt its actual detonation. If you're actually hearing something, it needs to be addressed.

I do know that I had a battle with a false knock condition recently, but it took a careful review of operational data using Tunerpro, looking at my spark plugs, and past experience with pinging (when I was trying to run ~10.2:1 compression) to determine that it was false knock being recorded by the ECM... partially due to a bad knock sensor, which I ultimately replaced with a Delco sensor torqued to 13-14 ft-lb.

If you had the ability to record data, you could see what the ECM is detecting via the knock sensor.

 

So far I have pulled plugs 1, 3, 5, 6, 7, and 8. 2 and 4 are blocked by ac and other stuff so I'm gonna fight them after this response. 1, 3, and 6 look perfect. However, 5 looks very white/gray on the electrodes. I believe this means lean. 7, and 8 have the "salt and pepper" look. Not as bad as it would exspect however (yay!). I'll attach pictures



Not sure how well it shows up

Im very curious about 2 and 4. Will update soon

 

Those don't look terrible but there are signs its running hotter on 5 & 7.

You need an OBD1 cable with USB connection and TunerPro or DataMaster software.

 

from your list, #6 should be at the top.
The spark plugs are crusted up, and that build up is also on the heads, valves, piston top, and when it heats up enough it will cause random detonation.
Way way back in the day, we had car engines with carbon build up and it would cause the engine to still run after turning off the key, it was dieseling.

I usually don't believe in a fix-in-a-can, but in this case I recommend you check around for some engine treatment designed to directly burn off carbon from combustion chambers, needs to be a lot stronger than a fuel system cleaner.

 

Where could i get a good obd1->usb? A couple different sites offer something like that

This seems weird to me but "steam cleaning" by using a squirt bottle to spray small amounts of water into the intake (through a vacuum line probably, I don't like the idea of my maf getting wet) came up alot when I looked up cleaning carbon deposits. Goes against everything I think I know about engines but people seem to swear by it. My other thought was spraying intake/valve cleaner through spark plug holes and down the intake. Thoughts?

 

yes indeed that water spray steam cleaning is a real thing and can be a fix. Easy to do on a carb engine and I even did it on the mother-in-law's cadi Northstar engine heh, no harm. But still, I would prefer a can of cleaner chemistry instead of water, and suggest spraying it into the intake with engine hot and running for max effect, whatever the directions on the can say.

 

Before you do anything more, check the timing. This should be your first step in diagnosing a detonation issue.

 

Finally checked the timing. It's 21° advanced with the brown wire pluged in, 6° with the brown wire unplugged. The knock sensor isn't plugged in so I suspect that's what's causing the 21° advance at idle

Any recommendations for a ob1 reader usb?

 

21 looks about right according to that spark map.