KR on '92 LQ1

[Shaun]

Hi guys. As some of the 60degree/W-body cross-forum members know, I recently picked up a '92 284-equipped Z34. One of the first things I did was toss a chip from Ben in to liven up the the car a little. I was out toying with my Tech I trying to solve an idle problem (and fixed it. thanks idle relearn!) when I decided to make a few quick runs scanning for knock. Through first and most of second I was seeing a near constant 4-5 degrees of KR and near the end of third, I was beginning to see 7 and even 8 degrees.

I'm mostly from the LG5 and L67 world where knock is a very, very bad thing. Are these motors prone to knock or should I begin to try and track down where this is coming from? Any help would be much appreciated.

[SappySE107]

These motors are prone to not knock actually. Maybe the injectors are clogged up or the knock sensor is touchier than others. I have seen a memcal swap fix the issue before, but the only thing I can say for sure is the tune isn't doing it. Clogged fuel filter possibly as well. Maybe cam timing from a stretched belt? You should be able to run regular gas without a problem, but midgrade for sure.

[RedZMonte]

i would start looking at maintence items, plugs, wires, timing, fuel filter, like ben mentioned. turboed with basicly a stock tune i don't have any knock.... "Hemi" style engines (plugs come in from top of head) tipically don't get KR unless something is wrong..

S

[pocket-rocket]

I would run some GM Top Engine cleaner too, before you swap out the plugs.

[Shaun]

Thanks for the advice, guys. Yeah, this is with 93 octane on a 30 degree night. Something is certainly off. I'm gonna replace the plugs, wires and fuel filter next week. Hopefully it'll clear everything up.

T-belt was checked before I even bought the car. Good shape, good tension. i doubt it slipped a tooth.

If it ends up being the MEMCAL I just give up on these damn cars. You know my story, Ben. hahaha

[SappySE107]

Belt can look fine, but stretch. Did you check the timing of the cam gears? It doesn't have to slip a tooth for it to be off. In time, it should idle smooth. With it stretched, you will start to notice a slightly rougher idle. Without experience, you might still call it smooth since it won't be real bad.

A cracked plug will cause all kinds of issues as well. I have had that happen.

[Shaun]

Plugs, wires and fuel filter and still showing 5-6 degrees of constant KR. Strangely enough, if I row through the gears, it only starts getting bad in 3rd gear. In other words, through first I might see 1 maybe 2 degrees, about the same in second, and then once I hit third it's 4-5-6 degrees. Don't know if it could be some false knock from the tranny or what (but I doubt it). Removed Ben's chip, put stock memcal back in, no difference. Don't know how to check the timing. I'm wondering if it's either a hyperactive knock sensor or a weak fuel pump.

[IsaacHayes]

Check the FP with a gauge, with vacuum and no vacuum on the FPR. What are the BLM/s and INT's showing? lean?

[robertisaar]

What are the BLM/s and INT's showing? lean?

X2...

and knock generally won't happen as much if at all in lower gears due to the engine not getting loaded enough to cause it.

[pocket-rocket]

X2...

and knock generally won't happen as much if at all in lower gears due to the engine not getting loaded enough to cause it.

I want to comment on this, but I won't...

[robertisaar]

I want to comment on this, but I won't...

wrong loaded, but pun has been noted.

[pocket-rocket]

wrong loaded, but pun has been noted.

Lol. I guess I shoulda put that smiley in my first post

[Shaun]

Well, I had a great scan of the car, but TunerPro decided that it wasn't important or something and deleted everything. Fucking hell.

Anyway, of the 2 seconds it actually did record, the BLM was 144 and the INT was 129. Not sure what that means or if it's good.

FWIW, we went out and scanned Chris' Z34 tonight and it showed very similar KR patterns. His car runs like a raped ape compared to mine, but I attribute that to mostly lower mileage. My engine was put in after the 60K mile LQ1 blew up and the last owner has no idea what the mileage is. I have a bad feeling it's pretty far up there. Anyhow, I'll be picking up a fuel pressure gauge on Sunday so we'll see what happens then.

I think the lower performance is just the symptom of a tired LQ1.

[robertisaar]

BLM of 144 means without O2 correction, the motor was running 12.5% lean, roughly 16.5:1 if it was in closed loop and attempting a target AFR of 14.7:1.

[Shaun]

BLM of 144 means without O2 correction, the motor was running 12.5% lean, roughly 16.5:1 if it was in closed loop and attempting a target AFR of 14.7:1.

Ouch. Let me try and get a good scan tonight.