General GVR4 Heavy knock under load

[seth98es]

This has been going on for a long time, so long I cant remember when it first started. Basically under a load, say 5th gear 60-70mph, going into boost is fine, at about 10-12psi I get a violent knock from the motor, it shakes really bad. Its not like its a misfire, I know what a misfire is, this is by far more violent.

For a tune, I am using a Keydiver chip on a 95 ECU, which is spot on 11.4AFR under full boost(not under a load).

Heres a few logs, only logging from the Pocketlogger for now as I need a laptop to log both the Pocketlogger and the Zeitronix at the same time.

http://www.iamsethmo.com/Logs

I couldnt see much wrong with the logs but timing looks to drop real bad when it knocks. Not sure if the knock is causing that or if its just because I lift the throttle as soon as it does knock.

Only possibility I can think of is that the knock is detonation or something. I had a timing belt skip on me awhile back, valves hit the pistons. I just smoothed out the sharp spots and got a new head. I cant remember if the problem started before or after the new head. Could it be hot spots on the piston tops detonating? What should I check for? Im just at a loss as it only happens when the car is under a load

 

[GVR4592]

I'd check the mechanical things first, boost leaks, fuel pressure, ignition timing, cam timing, knock sensor condition and torque, spark plug condition and gap and anything else you can think of.

Does the condition only occur at part throttle?

 

[seth98es]

Its not only at part throttle, if I floor it at 60mph in 5th gear, it will knock at 10-12psi. Im just too scared to floor it through the knock as its pretty violent. If I downshift into 4th at 60mph it pulls fine untill redline.

This has been going for at least 8 months. I have changed spark plugs several times, FP is set to 38psi with vacuum on the Aeromotive, knock sensor is about 2 years old I will check it of course.

 

[GVR4592]

Fuel pressure is supposed to be 43 psi with the vacuum line off on a 2g car.

 

[Module Unknown]

This sounds very similar to my problem that I've been fighting for months. Knock in 3rd gear through 5th gear under load to WOT. Sometimes I can make a 3rd gear pull starting below 3k and be good until 6k when it starts knocking. However, if I try and go WOT at say 4k or above it knocks instantly and continues to climb. Cruising in 5th on the freeway if I give the car a bit of throttle to speed up or try and pass a car it may or may not start knocking. I can't figure it out and it's driving me mad. Being a 2G I can't get an exact knock count, my my keydiver chipped ECU shows me that I am in fact knocking.

My wideband reads rich as hell at 9.0 to 9.5 a/f r, but leaning the car out only induces knock sooner and more of it. However, my narrowband O2 reading seems a little low at around .94v (not that I should be tuning off that), but then the car was running perfectly at 20 psi daily and a 10.5 a/f r it was reading .98v.

Since the beginning of this issue I've replaced my fuel pump, fuel pressure regulator (stock one wasn't working properly). Replaced my knock sensor. Done some headwork due to a snapped balance shaft belt. Balance shafts are gone now, 170psi in every cylinder, installed HKS 264 cams (had them and I was there). The cams surprising helped the issue a bit. Running 100 octane seems to get rid of the knock for the most part, but the only part of the fuel system that isn't new is my injectors. Fuel pressure was set at 43psi on 91 octane, currently 45psi base and still no help. Changed spark plugs many times since this has begun, wires, timing is dead on (base), cam gears are currently zero'd, cleaned my MAF sensor, there's no audible knocking from the engine. It just sucks that I can't safely run 15psi (lowest I can get my boost right now) when I used to be able to run 20-21 daily without any issues. I know your frustration!

A boost leak test last night found a leak from my throttle body shaft seals so I do need to replace those before I can test the system further.

I'm also thinking there may be an exhaust leak, possibly fromt he gasket between the exhaust manifold and turbo but haven't tested that theory yet.

Anyway, I guess I just wanted to subscrobe to this thread and share my problems and what I've done to try and adress them so far. In no way do I want to hijack the thread so to everyone, please don't reply to any of my issues to me in this thread.

I also have DSM link standing by, but have yet to install it before I clear up this issue in fear of this making it difficult to impossible to properly setup and tune DSM Link. We'll see... I might throw it in this weekend and hope that I can get a decent base tune and possibly get some more insight on the issue with the logging capabilities that will become available to me. If I figure anything out, I'll of course add to this thread.

 

[seth98es]

Thanks for your input man, glad to know that I am not alone! My motor is a 6bolt, FP is about 38psi with vacuum, 43psi without.

 

[FORMONTOYA]

Simple stuff first.

Do a boost leak test and fix any issues.
Check for exhaust leaks pre O2, a can of Seafoam works great for this.
Look at your fuel......log3 looks extremely wild: STFT = -13, LTFT = 13 at ~3K.

Your maxed out on your LTFT (+/- 12.5%, yours rounded off at 13) the whole way in the positive direction, yet the STFT is pulling fuel at anything above 2500RPM.

You rarely went WOT in any of those logs.

When you log do RPM, timing, STFT, LTFT, TPS, O2 (bank1), and knock. Plus include the WB readings even if you have to write them in; and since you have "boost readings" on your display. Write them in at the same RPM points as the log.

Do a 3rd gear pull from around 2500-3K and just floor it, we should see a TPS of 95ish or above if you're going WOT.

 

[seth98es]

My laptop comes next Thurs so I probably wont log anything untill then. Ill definitely make some better WOT pulls of this knock and get the wideband logged as well.

 

[seth98es]

Just to update things, I still havent figured it out. I have a new set of plugs, NGK BP6ES plugs along with 8mm Acell plug wires. The car runs perfect under boost with no gear load. What I mean by gear load is say your in 5th gear going 40mph, the knock will come into play when I ease into throttle and hit 6-10psi and then I let off as its violent, I dont want to brake something. If I am in 2nd or 3rd gear at 40mph and ease into WOT, I have no problem pulling to readline.

I still need to do some logs on the wideband, but I still need to order a USB cable from Zeitronix because my laptop doesnt have serial

It doesnt really affect my dailey driving as I can predict at about what point the knock will start, so I will let off before it happens. Or if I really need to speed up I will just downshift a gear and everything is fine.