Phantom Knock or Something Else?

[98GSX-WI]

It seems like being a DSM owner...eventually things that you read about on these forums seem to eventually happen to your own car....

Please diagnose what I am seeing... First off, yes I have a 2G....and yes, I can read knock...with a keydiver chip that reads knock on the factory boost gauge....

When I am in a high gear (4th or 5th) and at about 2600-2700 rpm....if I slightly open the throttle and let off a few times...I start to see knock...and if the knock gauge starts going up and I give it slightly more gas.....it goes up even more... This effect seems to be the most prevalent when the car isn't warmed up...but still exists even when the car is warm. I do not see knock when at a higher rpm (above 3K).

Other background: I have a FP Big28 turbo, but also have a problem with the turbo not fully spooling to 20psi in 3rd gear until about 3800rpm. So I'm thinking that I may have a boost leak or my wastegate needs to be adjusted....(I do have the 17psi actuator, though).

Question....is what I am seeing, phantom knock....or could a boost leak or a wastegate that is staying slightly open also cause real knock?

I've played around with the SAFC, adding or taking away fuel at the low throttle points....and that doesn't seem to help either. I also got 93 octane gas at a different station, thinking that maybe it was bad gas...that wasn't it either.

This didn't happen before....but recently I got a new downpipe to fit my EVO O2 housing. The flange that the guy had to weld on was not a flat one, but a round one (2 7/8")--they didn't have a flat 3"....so the guy had to weld on the outside and the inside to prevent leaks....but my wife swears she can smell exhaust now....(not sure if this would relate to the phantom knock issue though)...

Could it be that with the new downpipe, my exhaust is now resonating at the right frequency for the knock sensor to pick the noise up?

OK....sorry for the long post....but these are all of the factors that I can think of right now that may help in the diagnosis.... Anyone have a similar situation...please help....

 

[Jimmy Jr.]

I can't read knock but I have a 2g and I have the same type of thing happen. In 4th or 5th gear whenever I get on the gas a little bit a couple times it starts acting up.

 

[Sk8er07999]

I really doubt it's your exhaust. Remember a knock sensor is designed to pick up any metallic sort of knocking noise. With this said a number of things could cause this metallic knock. Since you said it happens when it's cold it could be an ever so slight piston slap that causes this (no biggey). Do you guys vent the bov? Maybe un burnt fuel building up giving you rich knock or a slight miss fire as you let off and push on the gas? As far as boost goes. Maybe the ecu has the fuel maps set to what it sees the driving habbits mostly being in the lower gears and for some reason when you get on the highway your boost builds differently the ecu doesn't know this and supplys fuel differently causing a slight misfire resulting in minimal knock sensor activity since it used to mostly city driving? Just some things to think about but I wouldn't worry about it.

 

[dave99gst]

maybe it didnt happen before because rits now colder out side and your lifters are making more noise? ( causeing phantom knock )
I no ive noticed sort of the same thing on my car ( with dsmlink ) sept' dsmlink flashes the CEL at you when it sees knock. I can at least change the points (both tps and rpm ) that the ECU should ignore knock.

 

[98GSX-WI]

maybe it didnt happen before because rits now colder out side and your lifters are making more noise? ( causeing phantom knock )
I no ive noticed sort of the same thing on my car ( with dsmlink ) sept' dsmlink flashes the CEL at you when it sees knock. I can at least change the points (both tps and rpm ) that the ECU should ignore knock.

I guess that is yet one more advantage of DSMLink. I haven't thought about lifter noise... That makes the most sense to me right now....because at low rpm--less oil pressure--more lifter noise....but I'm still not sure that is what it is.

The knock that I'm seeing occurs when I just barely give it some gas at about 2500-2700rpm (tested it again this morning). I am actually just tapping the accelerator a bit....and then if the knock starts occurring and I give is slightly more gas when the knock starts going up...it goes up some more....very mysterious to me....

To me, it actually is important....because whether real knock or not the ECU still pulls timing...

 

[Syndicate13]

I have been fighting this in my car since I've owned it. I think it's just something that you'll have to live with. In my own car I attribute it to lifter tick since my car ticks like mad when it's warming up. A member on here said he switched to Valvoline and tick went away and tomorrow just so happens to be my oil change so I'm going to try it. Mine usually goes away after the car is fully warm and doesn't come back. Before my chip and now DSMlink I had no idea what was happening. Sometime my car would just spool fully and feel like it was struggling to move. If I let out of it and then get back in it, it would accelerate normally. Like Dave said, DSMlink gives you the option to ignore the knock sensor at low RPM and throttle position. I'm a bit hesitant to try this on my car since it doesn't really bother me. I wonder what Kyle would have to say about this as he's pretty familiar with the ECU code. I used to think it had something to do with the BCS flicker that happens between 2300-3900, but since DSMlink is supposed to remove that and I still get it I don't know what to think.

 

[98GSX-WI]

Update:

Problem has been solved! First I tried Valvoline oil treatment...didn't help a bit...still had lots of knock between 2500-3000rpm. Then put in a can of Restore Oil Treatment....and no more knock at lower rpms.... I was skeptical that the knock was due to lifter tick....but I am believer now...

I'm still amazed that the stuff actually worked...but nevertheless, I am very happy now....that low rpm knock was a big pain in the $ss....and was very annoying....

Now I just need to get rid of an apparent boost leak or wastegate problem...

 

[ukyo]

Interesting... My GSX does the same thing with the knock in the 2K RPM range. I've about had it, so I'm willing to try anything to make it go away. I was just about to drop some cash on a new knock sensor, but I'm going to give this Restore Oil Treatment thing a shot first. I'd hate to replace a good knock sensor and still have the same annoying issue.

I'll post back with results...

 

[ukyo]

Well, I'm speechless. Literally.

I've been dealing with this stupid PK for... ever??? And now, with one little $5 can of snake oil, it's gone. *POOF* In to thin air like it never happened. I expected it to take a few days, and it would slowly get less and less until it was gone. Nope. I poured the Restore in, cranked the car (car was dead cold), drove about 1/2 a mile, and never had the CEL come on from timing being pulled (DSMLink). Car pulled smooth all the way up to 4K RPM while it was still below average operating temp. Something I haven't felt in years.

It's too good to be true. There has to be some kind of a seriously bad side effect to using this stuff...

 

[ukyo]

Looks like I spoke a bit too soon. While the PK is much, much better, it's not gone. I still get it every now and then. While it's no where near as frustrating as it used to be, it still sucks.

Since it's obviously something with the engine being cold (almost 100% oiling issues until it's warmed up), would it be beneficial to run something like Sea Foam or BG Clean on it?