Lean at idle, rich at WOT, knock from 2k to 3k RPMs. Please help!

streetdsmpwr · 05-05-2012, 08:06 PM

Me and my friend installed FP 1x cams, evo 8 beehives, revised lifters, and all of the timing belt stuff a few months ago on my 99 GSX with 60,000 miles on it. The car ran ok, but it had a little rough of an idle. I assumed it was just because of the cams and needing a new tune. The car sat for a little while after.

A few months later, I installed an FP Exhaust Manifold and decided to re-tune the car for speed density. I had installed the Omni 4 bar MAP sensor and GM IAT a few weeks prior, but I was still just running off the MAF. I re-flashed my ecu with a new tune (I use ECUFlash), but still just ran off the MAF for the time being, as I had to set up my VE table. After the re-tune, my car started running like absolute crap. It is very lean (from 16:1 to 21:1) at idle on start-up and stalls often. Once the car warms up, it will run much better, but it will still occasionally stall.

When I go WOT it will be very rich (10:1 to 9:1) even though I have it tuned for 11:1 AFR. I assume that the richness is due to the knock I am getting from 2000 to 3000 RPM on light acceleration. I did not get the knock before the re-flash. It doesn't happen all of the time, but enough (I assume) for the ECU to switch to the low octane fuel and ignition maps. It seems to be phantom knock, as I don't hear or feel it and it will be large counts like 10-15. When it does knock, the AFR's are around 14:1, so it shouldn't be a lean condition causing the knock.

My fuel trims are now maxed out (positive) even though I had them down to +0.50% before all of this happened.

I have tried a different TPS (off a running car), different front O2 (off a running car), and re-flashed my old tune, but nothing has worked. Please help! Thanks in advance. My profile should be up to date on my setup.

PieEyedPiper · 05-19-2012, 10:51 AM

Can you post a log?
If it matters, I'm experiencing the exact same symptoms. This 2-3k thing is driving me mad! I'm going to be playing around with a stock tune today to try and see if I can eliminate it, otherwise I'm just going back to dumbing down the knock sensor before 3k. ...But I hate that, too many unknowns for a guy with no cash for new pistons.

streetdsmpwr · 05-20-2012, 10:17 AM

Quote:

Originally Posted by PieEyedPiper

Can you post a log?
If it matters, I'm experiencing the exact same symptoms. This 2-3k thing is driving me mad! I'm going to be playing around with a stock tune today to try and see if I can eliminate it, otherwise I'm just going back to dumbing down the knock sensor before 3k. ...But I hate that, too many unknowns for a guy with no cash for new pistons.

Evoscan is blue screening my lap top lately, but I'll try to get a log. Have you done anything to your car recently?

Black95awd · 05-20-2012, 10:32 AM

Mine is running 22.4 at idle and 7.4 under 20-30% throttle and zero boost. If I can keep 5-15% throttle it will run 12.5 or so, still not running any boost. Also my fans do not kick on, 3g ecu, ceddymods for 2g.

PieEyedPiper · 05-23-2012, 08:10 PM

Quote:

Originally Posted by streetdsmpwr

Evoscan is blue screening my lap top lately, but I'll try to get a log. Have you done anything to your car recently?

Nope. It actually seems as though I've always had this knock since I started modding the car. I get the same knock on a stock tune. It's only because of ceddymods that I can now monitor knock directly and it certainly seems to explain why the car is so "hot and cold".
I might just have nasty phantom knock after all. It just seems like that'd be reserved for slap happy je's not oem pistons.

perks563 · 06-04-2012, 09:43 AM

*I am by no means an expert on tuning*

Ok, so have you considered that it is phantom knock? I had the same thing and the guy tuning my car (he has an ad in the Freelancer section) said that it is phantom knock that was appearing. You said that you are at low RPM's and light throttle, so the engine isn't under a large load and should not expect knock at those conditions. How much boost/airflow are you at when you are seeing these counts of knock? I'm guessing not too much. Is there a way that you can adjust the setting on the knock sensor? In Link, you can set RPM and throttle position that it will read the knock. So for example, you can set it to 'turn on' at greater than 30% throttle above 2200 RPM's and below either of those two conditions the knock sensor won't register.

Hopefully someone else can chime in about this. Hope what I said makes sense and helps.

KevinRR · 06-04-2012, 10:01 AM

I had the same problem with my car, it would always knock at around 2.5k. I did what pers563 said and set ALS/Knck >= 2500rpm and >= 25% tps. It been fine and have not knock since I set it.

streetdsmpwr · 06-04-2012, 06:14 PM

In ecuflash you can adjust the knock sensitivity at certain rpm's and loads, so I can get rid of it that way if I want. It is knocking while it is still in closed loop. I am still replacing one possibly problematic sensor at a time to try to get to the bottom of this before I start messing with knock sensitivity.