Ive replaced my tired tbi 350 with a 350 HO wanna be.....gmpp alum intake, vortec heads, headers.....cams a weee bit milder than the HO. It ran lean as hell as expected with the stock chip so ive burned about 30 ...at first i just adjusted the VE tables and i got improvement and now ive been tinkering with the "pumpshot" tps and mav vs accel....i have gotten these values ENOURMOUS...over 200% and it still knocks under high load..whether i mash the pedal or put it in 4th when i should be in third do get a "load effect". nothing seems to help....fuel pressure is the stockl regulator cranked and so now i begin to wonder if im not getting enough fuel....i didnt think i would need bigger injectors for these few mods....any ideas???

 

If changing the fuel doesn't or has stopped making any changes in what you're doing, then look at the timing. Try ramping the timing down faster.

Thou, you might not have enough fuel in the 80-90 K/Pa areas.

Might look at dropping the TPS PE thresholds.

Things are a balancing act, and the lines blur at times.

 

Does it knock all of the time you are into the go-pedal? Or just the first time?

From your description I'd venture a guess that you are using the '7747 ECM? This ECM forces the engine to knock as part of the diagnostic routines.

If it is continous knock I'd back off the timing tables until it stops. Or the engine doesn't run correctly and another problem has been found (IE: switched or arcing plug wires. . .).


RBob.

 

it is a 7747 and im not sure i understand what you mean about knocking all the time.....i cant really get on the gas cause when it gets a load on it....above 70 kpa ...sounds like theres marbles in the engine....were not talking about my computer screen saying the engine knocked....i can hear it loud and clear....if i do it real slowly i can hear it before the knock sensor kicks in. But in any situation if I floor it it knocks.......knock sensor retards timing and then my ses is on. like i said earliar i cant imagine it needing this much extra fuel, my tps and map vs accel values are over double and it seems that the stock spark advance is mild enough i wouldnt have to retard it any more....one othe thought i had was everything ive read said my stock motor is 8.3:1 compression......im 9:1 now, could that cause that much of a change??i think a wideband is going to be the most help but any advice will gladly be taken.......thanks a lot guys. hopefully i can get this pixed before my rings are non existant

 

Going from 8.3:1 to 9:1 CR is significant enough to matter. You might also recheck your base timing...if the distributor has slipped, you might have a lot more spark advance than you think.

The WB will be a big help in determining if lack of fuel is involved.

 

Sure sounds like a mechanical problem, or a missed item in tuning.
If your hearing knock, that means it's more then the limits of ecm can handle to you're talking of like 20d of excessive timing.

Fuel filter, plugs, wires cross firing, check all of it again, would be my advise.

 

Your description of the problem is what I meant about knocking all of the time. Hmm, SES light too. If that is a code 43 . . . Do you have a data log that shows knock counts during this period of time?

I am wondering if this is the forced knock and the knock detection system isn't working, so the ECM keeps trying. It is either that or there is flat out too much timing. What octane gas?

Does the knocking stop once the SES illuminates and you get into the pedal again?

Can you post a data log (that covers the knocking) and your bin.

RBob.

 

i did some checking and if the compression ratio stock was 8.3:1 im up over a full point to 9.35:1 hmmmm??? checked plugs, wires, dist, everything was good.....i will change fuel filter and log the spark counts tomorrow and post them asap...about getting on the pedal after knock and ses and ecm retards timing....havnt really tried it, ive gotten in the habit of driving like a granny in order to save the motor, but i will give it a wing in the morning.....gas is cheapo 87 octane...when i put the motor in i ran nothing but 90 but it made no difference and the bank account wasnt liking the price.

 

well i tried to see if it would do it after it flashed the code 43.....the first time i opened it up it knocked as expected and i felt the timing retard at the ses came on.....then i did it again and no id didnt knock like it does before...but it has no power whatsoever probably cause it has no timing after the code 43, garage is warming up as we speak to put in fuel filter(im in alaska buuurr) the spark table is a stock ASDX bin....what my truck originally ran. doesnt seem to me that there is some major mechanical problem cause it only does it under high load, just cruising around town its not so bad...allthough it could be better.....might go back to stock ignition.....this motor never ran on the stock one, when i switched motors i put an msd 6a in, i cant say why that would be a problem but its just another thing to try. Oh yeah, the distributer is right on soooooo......i still have this feeling that im not getting the fuel i need. seems like a lot of people doing the same mods i did switched to 454 tbi's and injectors and i havnt got an email reply from the wide band pcb guy.....i think that will help narrow it down a lot....if that reads good ill have to make sure i didnt put the cam in backwardsand i didnt forget about those logs.....couple hours and they will be up
thanks a lot guys

 

oooooooooook.........totally lost as far as knock goes, with win aldl i only get 1 or sometimes 2 and thats on startup.....dont get em anywhere else not even when it sounds like there a whole bag of marbles in the cyliders........all i get from that when its extreme is a code 43....and i dont even always get that unless its real bad. why wouldnt it count that as a knock??fuel filter had no effect. how do i go about posting my logs on here??

 

This is what I was afraid of. Remember that I don't have data logs and such to examine, even WinALDL doesn't give enough info. However, I do know what goes on inside of that '7747 running your engine.

The '7747 ECM forces knock in order to test the knock (ESC) system. From what I am reading/seeing the ECM is doing just that. The problem is that the ESC system is either not reporting that knock, or the ECM isn't seeing the report of knock.

After two failed attempts to force knock the ECM will set code 43.

Does it seem to you that the first two times (with the engine up to temperature) that the engine is pushed it knocks?

If so then I would check/test the ESC system. Check that the knock sensor wire & connector are in good shape.

RBob.

 

now that you mention it it does seem that i can get it to knock audibly the first time with out it throwing the code and then it throws the code on the second one....it will also pop the code when i go on long drives where im in OD for a long time at a constsant rate...those times it doesnt do it enough for me to hear it...also throws the egr code in those situations sometimes.......i just got all kinds of problems i have an extra esc that came with an ecm i got on ebay.....those things are the same on everything im hoping...and i will probably get a new plug for my knock sensor...i know the plastic cracked but it was still on there ok so i let it go. Im still puzzled why it would knock that extreme and only when its under a high load???

 

It is all in how the ECM does it. The forced knock test is only done in PE mode. First time adds about 12 degrees of timing, if that fails, next time in PE mode will add in 22 degrees of timing (cal dependent). That is a lot of timing to just add on top of whatever timing there is.

There is a patch to eliminate the forced knock test. Over on the diy-efi incoming area the file is called ESC_747.ZIP (may be in lower or mixed case, UNIX box). The patch is called ESC_DONE and everything including instructions to apply are included.

Apply that patch along with repairing the ESC system and your good to go.

RBob.

 

No there're not.
There's an easy 4d level of detection difference between some. You need to be good at plug reading to play the ESC/Sensor swap game. Make that real good.

Not to mention running too rich, and changing the acoustic signature of the engine to where things get really kinky.

 

well........i have had that motor in my truck almost exactly 1 year today and for the first time ever i got to mash the pedal to the floor and feel some ponies!rbob........you were about 100% right on, put a new knock sensor in and she runs like a champ, i still have a lot of tuning to do on the fuel and timing but man......1 year of frustration and it all came down to a 40 dollar sensor. I dont care how much you guys hear it but its not enough.....THANKS A LOT....not only for this help but reading all the imformation on here has taught me so much......rbob, grumpy and craig moates......man the world needs more people like you!and everyone else that is so helpful here! you guys ROCK:hail: