2500 rpm knock!

[Black94DSM]

Ok so I searched for a bit and still dont know whats going on here.

I have a 92 GS-T as a Daily Driver, and this car knocks like crazy when I hit 2,500 rpm. It does this always.

I could swear that I put the balance shaft belt on correctly as far as lining everything up, but is it possible if it is off, will it make the engine knock at a consistant rpm? It goes away around 3,000 rpm...or a little later.

The spark plugs are new, the spark plug wires look good. There are some slight boost leaks ( but ive never had this type of problem with boost leaks). Will a hacked MAS do this ? The previous owner put on a hacked 1g mas.

I need opinions on this please.

Thanks for the help.

 

[hatch]

Does it do it just revving the engine in neutral? Or does the engine have to have a load on it for it to knock? It sounds weird that it would only do it at a certain RPM. When you say knock do you mean as in some kind of interference in the motor or do you mean knock as in early detonation? I'm assuming the later. Does it just hesitate as in like a misfire around those RPMs? Have you pulled the plug wires to make sure there isn't oil or water in the spark plug wells?

 

[JayRolla]

Yea do you mean a knocking sound or detonation on the logger. If you are detonating that low of rpm and not in boost I would guess its phantom knock.

 

[BUCK]

I could swear that I put the balance shaft belt on correctly as far as lining everything up, but is it possible if it is off, will it make the engine knock at a consistant rpm? It goes away around 3,000 rpm...or a little later..

- Any Oil Pressure changes lately? - Within in all likelihood it;s your Balance Shaft rattling in it's BEARINGS - Which is why you ABSOLUTELY should have deleted them while you were "in there" ....

 

[Ravenous]

I just ran into the same problem and for the life of me couldn't figure it out. My base timing had wandered or I messed up when setting it the first time. I was running a base of 15 degrees advanced, which made my car knock in almost all situations. I'd check it to just be safe.

 

[Black94DSM]

- Any Oil Pressure changes lately? - Within in all likelihood it;s your Balance Shaft rattling in it's BEARINGS - Which is why you ABSOLUTELY should have deleted them while you were "in there" ....

Bolt-on Modifications
PTE 50 Trim turbo, Slowboy Racing Exhaust Manifold, Victory Performance SS o2 Housing, Tial 38mm External Wastegate, Buschur Racing Down Pipe / Test Pipe / Cat Back, 255hp Fuel pump, Maf-T w/3" Maf, 850cc Injectors, DSMLink, JM Fab SMIM, Slowboy Racing Race IC Kit, Tial BOV, Shep Racing Trans, Autometer Gauges,.....im sure there is more.
Engine Internals
Comp 200's, 5 Angle Valve Job, Mild Port Job, Multi Layer Head Gasket, ARP Head Studs.

Not trying to sound like an ass here, but if you read my first post you would see that this car that I'm talking about is my 92 GS-T. The specs you pulled from my profile are from my summer 94 AWD car.

This GS-T is stock besides an exhaust system.

Yes by knocking im talking about detonation. The logger shows that around 2,500 rpm under normal driving conditions the engine will go from lets say 35-40 degrees of timing all the way down to around 10.

My base timing is set to 5 degrees btdc.

It does not pull timing out at a free rev in neutral.

No oil pressure lose that I know of.

Does have lifter tick..., but im sure thats not the problem. Ive had motors with far more lifter tick than this one and not pull any timing.

 

[BUCK]

Sorry about that - I'll edit - I DID read the Post but obviously I didn't ABSORB the Post ~! - & my bet is still B/S Bearings.

 

[Ravenous]

Just covering all the bases here, did you inspect the knock sensor. I had one that was actually missing all of the black goop... read knock fine though .

 

[JayRolla]

Not trying to sound like an ass here, but if you read my first post you would see that this car that I'm talking about is my 92 GS-T. The specs you pulled from my profile are from my summer 94 AWD car.

This GS-T is stock besides an exhaust system.

Yes by knocking im talking about detonation. The logger shows that around 2,500 rpm under normal driving conditions the engine will go from lets say 35-40 degrees of timing all the way down to around 10.

My base timing is set to 5 degrees btdc.

It does not pull timing out at a free rev in neutral.

No oil pressure lose that I know of.

Does have lifter tick..., but im sure thats not the problem. Ive had motors with far more lifter tick than this one and not pull any timing.

What do you mean it pulls timing? If you have a logger log knock! Timing can cylce under normal driving conditions. Also usually your car wont knock under normal driving conditions and no boost, expecially on the stock rich fuel curve.

If you dont see any knock under boost I would suspect phantom knock when cruising.

 

[Defiant]

I'll put $20 on Buck's bet. At 2500rpm, the balance shaft is hitting 5000.

 

[Black94DSM]

Defiant is probably right.

This morning when I drove to work a few times going through the gears it didnt have any problems at all. I would say that for the most part 90% of the time it knocks and pulls timing. Would the balance shaft do this? I would think it would be all the time..but maybe not.

I know that while at a cruise the timing cycles. Thats not the issue here. I actually get knock and then timing gets pulled.

The Knock sensor is good, nothing is leaking and its not gooey.

 

[Defiant]

A failing balance shaft bearing could put out a sound that would mislead the knock sensor.
In the olden days, when knock sensors were just starting to be used, it was great fun to sneak around to the rear of a car a fellow mechanic was trying to tune and start tapping on the exhaust pipe with a wrench. The sensor would kick in, timing would go haywire, and he'd not hear you over the engine. We would laugh and laugh, until someone lost an eye.

 

[AlphaAssault]

I have a similar problem. However, my car just started doing it the other day, out of nowhere. One day it drove fine, the next it knocks at 2500 rpms and I get a CEL. If i rev the engine in neutral, everything seems fine. If I drive it normally, it stutters every time i stray into boost territory. I drove it past 2.5k rpms in 1st gear a few times without the lurching, but I didnt have any boost built up either. Could my problem be similar to the OPs, or are we talking about 2 different things here?

 

[Black94DSM]

I have a similar problem. However, my car just started doing it the other day, out of nowhere. One day it drove fine, the next it knocks at 2500 rpms and I get a CEL. If i rev the engine in neutral, everything seems fine. If I drive it normally, it stutters every time i stray into boost territory. I drove it past 2.5k rpms in 1st gear a few times without the lurching, but I didnt have any boost built up either. Could my problem be similar to the OPs, or are we talking about 2 different things here?

Sounds like we have the same problem here. Every once and a while my car does break through the barrier and not knock.




Defiant - Thats just wrong man...

 

[Littlebeeper]

my car is doing the same damn thing. it idles fine and runs perfect. it knocks at around 2000-2500 rpm. i think its a bearing but my balance shafts have been removed. well thats what i was told. the front one is gone because it has a bolt where the pully went but the rear one might just be in there. the damn car Vibrates like crazy when its idles lower than 1000rpm (it has always shook, even before the noise). guess its time to drop the pan and check. there are metal filings in the oil in the head so i know it ain't nothing good.

 

[AlphaAssault]

I dont really think my problem is the balance shafts because the whole car shutters upon entering boost. Its not just the engine vibrating, I can feel the whole car shuttering and bucking. Do you guys feel the whole car shutter, or can you feel the vibrations coming directly from the engine?

 

[Black94DSM]

Bringing this back up.

My car actually started to pulsate while driving in the 2500 - 3500 zone. Its like it loses power then gains power kind of like this if you have a creative mind.

ooooOOOOOooooOOOOOoooooOOOOOooooOOOO

I think my issue is more realted to the maf sensor or fuel related.

But man it is annoying.

 

[AlphaAssault]

You and I have a similar isue, i think. Obviously, Im not there to see for myself what your car is doing. I figured out that the MAF is dead/dying on my car, so I bought another one, all stock. Cant tell ya if it was the MAF, since the 'new' one hasnt gotten here yet, but Im willing to bet that the MAF is in fact your problem.

 

[Black94DSM]

I'll be trying my friends maf here shortly to see if it was in fact the maf. I'll let you guys know when I do this.

 

[wannarace]

Don't know if you figured it out yet or not but I just went through the bucking when boosting and knocking while cruising. Changed out my FPR and fixed bucking problem. I'm still knocking at cruise (5th gear 50-60mph) 42-43 counts. trying knock sensor swap tomorrow.

 

[AlphaAssault]

new MAF fixed my problem. Car drives like a dream now. new MAF is worth a shot.

 

[wannarace]

The only thing is that i'm using the MAF-T and 3.5" gm sensor. i found a way to do a round about test on it, it's either that or i see it could possibly be the EGR. At cruise, from looking at MMCD. it looks like some of the knock is comming from lean spikes. the higher counts are unexplainable. which brings us back to MAF or EGR. will let you know what i find. thanks for the feedback bud.