DAVE00

iTrader: (10)

Okay guys, still can't figure out my knock and severly split BLM issues. Here's what I've done so far:

• Changed all spark plugs and gapped at .45
• OHM'd all spark plug wires and all check out
• Cleaned MAF
• Checked for Vac Leaks with Propane - not a single one found
• Zero Exhaust leaks at headers or collectors
• New Knock Sensor
• Fuel pressure holding and new fuel pump (Racetronix) and Racetronix hotwire kit
• New O2's and they are fluctuating normally
• Tightened down alternator
• NO CODES being thrown

Okay, now that I've said that, my problems are I am picking up knock (not audible) on datamaster and its pulling upto 12 deg timing - ONLY AT IDLE. The IAT, MAP and IAC are all responding and parameters within spec. The only thing that is new is the injectors - FAST 42's.

Do my problems seem like they could be sticking or leaking injectors? It's hard for me to see if they are leaking as I can't lift the rail with it pressurized as these injectors won't allow the clips to be installed and the pressure pushes them out when I lift it from the manifold. I'm inclined to send these suckers off and get them professionally flowed and cleaned. Is there anything else that could cause these issues?

Big Al

iTrader: (1)

I believe you have a spare knock sensor. If you do unplug the one on the block and plug the spare in. Wrap it in a rag and see if you still get knocks. You may be chasing a different problem.

Al 95 Z28

LSWHO

iTrader: (1)

split blms are probably from your throttle body.

DAVE00

iTrader: (10)

Problem is you have to ground the sensor?

DAVE00

iTrader: (10)

BBK 58mm - and new gaskets. This didn't really start until the injectors?

stevo9389

well the TB is something to consider anyway. i just read this a couple days ago
http://www.noid.org/~lj/PCM%20Tutorial/SplitBLMinfo.htm
would be worth a shot considering it would be a lot cheaper to experiment with than injectors.

DAVE00

iTrader: (10)

Thanks for the help man, but I've been down that road and my BBK is an earlier model that doesn't have those cutouts into the throttle openings. Mine has a single hole very similar to the stock tb and I've already drilled out the IAC passage to match the stocker. My IAC counts are well in check and around 30-40 once hot. This is not my issue and the split BLMs are coming from somewhere else.

DAVE00

iTrader: (10)

Anyone????

purpleflamzz

do you have solid lifters? mine was throwing knock real bad due to my valves being a bit loose once i adjusted them it was fine.

DAVE00

iTrader: (10)

Nope - ls7 hyd lifters.

LSWHO

iTrader: (1)

Switch out the injectors then. If it goes away, it's pretty straight forward from there.

DAVE00

iTrader: (10)

My question, is does my issues sound like they could be caused by the injectors?

purpleflamzz

K was reading last night about the fast injectors and came across this,
*Note: low-impedance injectors can not be used with OEM computers
do you have high impedence or low impedence injectors?

purpleflamzz

heres this too. think this is definitely your problem call FAST and they can tell you.

Low impedance VS high impedance –which do you need?
FAST™ offers fuel injectors in both low and high impedance versions to cover all of your EFI performance needs. So which is the correct impedance to run? As a general rule, you will need to run high-impedance injectors whenever you retain your factory Engine Control Unit (ECU). Failure to use high-impedance injectors with a factory EFI computer will cause severe damage to the ECU, necessitating a costly replacement computer. FAST™ offers high-impedance injectors up to 60 lb/hr, so we’ve got you covered for nearly any performance scenario where you would still want to use your factory computer.
Need more information about fuel injectors? Contact our EFI HELP™ specialists at (877) 334-8355 for some expert advice.

DAVE00

iTrader: (10)

They are the High Impendance so that's not my issue. Actual part number is 304208.

Bad94

iTrader: (1)

im having this same exact split BLM problem. but i dont have the knock

im pretty sure we have the same exact cam 230/236 on a 108LSA

i thought i had it fixed yesterday. i moded the intake and monoblade to use the IAC passage. drov eit around a good while came back and it was idling with both BLMs at 120(still base tune, trying to get the split figured out)

today they are as bad as last week. the only change made after driving it yesterday was i took the made in japan denso O2s and put in made in usa delcos. gonna go drive it a while today and see if it straightens out.

one thing i noticed with the denso O2s was the KOEO scantool showed .08v delcos show .450v

what is your idle RPM? at first i was at 800 then tried 700 for more lump on the idle. i just bumped it back up to 800.

how much split do you have is it only at idle like me?

right now i have 158 on bank 2 and 130 bank 1

have you checked your cylinder temps with an IR gun?

what do your plugs look like? front 4 on mine are lean back 4 look good. no real noticable difference side to side

LSWHO

iTrader: (1)

I'm gonna go ahead repeat myself and say it's your throttle body. And it's obvious you didn't read what you were linked otherwise you'd see your fix involves much higher iac counts to try and correct the split BLMs in some aftermarket TBs and higher overlap cams.

DAVE00

iTrader: (10)

I have read this same post many times when I was trying to correct my split BLM's in the past and if you search my post history you will see that. How do you suggest I fix my TB as it matches up perfectly with the IAC passage and as stated does not bleed into the TB openings as most aftermarket TB's? Here is a pick of mine:



Honestly, this major split blm - 100-160 just recently started - close after the injectors and that is why I am thinking it could be them?

DAVE00

iTrader: (10)

Yup, our cam is very similar if not the same LE cam. I went with the 42 injectors as my 30's were maxed out at 100 at WOT. My idle is set at 950, higher than yours, and I have a very large split at 100-160(passide) and I'm starting to think that the lean condition on the passide is actually causing it to detect some knock but not sure. With my IR gun the cylinders don't look that diff in temp, but Cy 7 is a little cool as well as Cy 2.

Same here on the plugs and I replaced them anyway to make sure one was not fouled.

LilJayV10

iTrader: (39)

I could be wrong but I think it's because of the intake design when using a larger camshaft. The way the air resonates inside the intake causes one side to be different. I believe that there are ways to help the situation buy adjusting your throttle body. Which may have been mentioned in a previous post but I didn't read the link.

There was a good thread about this on camarz28.com a while back. I will see if I can find it.


Well crap. I just read the link posted earlier and that's exactly what I was talking about. Carry on.