2001 4.3 Vortec sensitive to timing

[gnnova]

I have a 2001 4.3 vortec in a S-10 Blazer that I have that seams to be very sensitive to timing. It is stock except for a cam from a mid 90's CPI 4.3 and 36lb injectors for a tail pipe turbo that I want to do down the road. I have been trying find a missfire under lite load also that be causing my issue also but not sure. I have replaced the 02's, distributor, cap, rotor, cam sensor, wires and plugs with new ones. Swaped out the MAF, throttle position sensor, IAC, EVAP soleniod and MAP sensor with known good ones. Set cam sensor to 0deg. Smoked the intake for leaks and found none. I have pulled as much as 12degs of timing out from the stock tune in places to prevent knock. Could someone look at my tune and see if there is something that looks like it could be causing my knock issue?

[blindsquirrel]

I am not a V6 guy, but... your injector data looks hinky. You have a flat flow rate table, but the offset vs volts vs VAC is sloped, as it would be only if it had no rising-rate regulator (which I believe they do stock, as stock files have both IFR & offset tables flat).

What injectors, and where'd the data come from?

[blindsquirrel]

Also... if you go ahead and apply one of the speed density OSes you won't need to have the high & low octane spark tables the same. That probably doesn't help if it's knock-sensitive.

[gnnova]

I am not a V6 guy, but... your injector data looks hinky. You have a flat flow rate table, but the offset vs volts vs VAC is sloped, as it would be only if it had no rising-rate regulator (which I believe they do stock, as stock files have both IFR & offset tables flat).

What injectors, and where'd the data come from?

I bought the Injectors from AUS Injection (part 10722-380) and the injector data they gave me did not ask whether I had a return type fuel system or not. So I just put the data in from the table that matched my X and Y labels for the offset table. I looked at my stock offset table and you are correct that it is flat from 0 to 80Kpa which lines up with what you said for a return type fuel system. With that being said, what column's numbers should I pick to populate the table with. From column 0 or a different column?

[blindsquirrel]

With a referenced regulator, both the flow rate & offset use only the 0 kPa column for the whole tables.

[Alvin]

I have a 2001 4.3 vortec in a S-10 Blazer that I have that seams to be very sensitive to timing. It is stock except for a cam from a mid 90's CPI 4.3 and 36lb injectors for a tail pipe turbo that I want to do down the road. I have been trying find a missfire under lite load also that be causing my issue also but not sure. I have replaced the 02's, distributor, cap, rotor, cam sensor, wires and plugs with new ones. Swaped out the MAF, throttle position sensor, IAC, EVAP soleniod and MAP sensor with known good ones. Set cam sensor to 0deg. Smoked the intake for leaks and found none. I have pulled as much as 12degs of timing out from the stock tune in places to prevent knock. Could someone look at my tune and see if there is something that looks like it could be causing my knock issue?

As knock sensors age they either get crazy over sensitive or go completely quiet. 22 years is long enough to maybe try a new GM set of knock sensors

[gnnova]

With a referenced regulator, both the flow rate & offset use only the 0 kPa column for the whole tables.

Looks like I have more tuning to do. A huge Thank you.

[gnnova]

As knock sensors age they either get crazy over sensitive or go completely quiet. 22 years is long enough to maybe try a new GM set of knock sensors

Point well taken. I'll try a new one.

[blindsquirrel]

Did lowering timing affect the amount of KR it showed? Generally, if you change timing (and octane, best to do both at the same time) and the KR doesn't change, then it's picking up some noise that isn't spark knock.

[gnnova]

Did lowering timing affect the amount of KR it showed? Generally, if you change timing (and octane, best to do both at the same time) and the KR doesn't change, then it's picking up some noise that isn't spark knock.

I have searched for anything that could be rattling or contacting the motor to cause false knock and did not find anything. The knock is odd though because it was only 1 or 2 deg. I would pull that amout of timing out of those sells and it would still be there until I got to were I'm at now with some cells being as high as -12deg from the factory tune. Some cells are not down at all from factory. I have a new sensor coming from rockauto. We'll see when it comes.

[STAGEUP]

I have searched for anything that could be rattling or contacting the motor to cause false knock and did not find anything. The knock is odd though because it was only 1 or 2 deg. I would pull that amout of timing out of those sells and it would still be there until I got to were I'm at now with some cells being as high as -12deg from the factory tune. Some cells are not down at all from factory. I have a new sensor coming from rockauto. We'll see when it comes.

Another thing that can cause too much preignition is carbon buildup on the piston surface. Just something else you can look into.

[gnnova]

Changed the Offset table yesterday to blindsquirrel's recommendation of the same values from 0 to 80 kpa due to having return type fuel system. When I tuned for the change in SD mode the ve table did not change alot but it felt better.. When I re-enable the MAF, the misfire was back. Did not hook my scanner up to see how bad it was. but the torque converter unlocked when it should not have, so more to come with that. I put it back into SD mode and tried putting the timing back to factory settings. The motor was able to tolerate the factory timing settings now. Something I notice during this was that in SD mode I do not feel the misfire but with the MAF enabled I can feel the misfire. I have previously tried a different MAF and it made no changed to the misfire. So thanks blindsquirrel's for the offset table suggestion. It is nice having it running much better now even if I can not enable the MAF for now. So if anyone has any ideas on the misfire. I'll get the new knock sensor in and see if I can actually be able to add some timing. Thanks everyone for trying to help.

[gnnova]

Finally got the Knock sensor in and my knock sensitivity has gone away. Thanks Alvin for the suggestion. Now that I can add some timing, I was looking at the stock timing tables at .68 and .72 Kpa areas (WOT area on my engine) and above 2600rpm. They look conservitive at a maximum of 23 deg's. Does anyone have experience with the 4.3 Vortec if it can tolerate more timing than this at WOT. The combustion chamber is the same as a 96 to 2000 vortec 5.7 V8. My experience with old SB chevy heads, we would run from 32 t0 36 degs of total timing but I know the chambers are more efficent on the newer heads.

[silowrado]

how do you like the aus inhectors? been looking into them as opposed to a marine intake for when i turbo my 99 4.3 silverado

[Life is an Enigma]

Here's a tune I've been working on for my 2004 Chevy Blazer with 4.3 just got the timing mostly worked out. No knock. Maybe it might help you.K&N cold air intake and no cats. Off-road tune /track only. The EPA & C.A.R.B are always watching nowadays. You're not paranoid if they're really out to get you.
DL 07-29-23 Timing + MAF.hpt

[Vbb1994]

The EPA & C.A.R.B are always watching nowadays. You're not paranoid if they're really out to get you.
DL 07-29-23 Timing + MAF.hpt

Right? Im shocked people come on here asking for help deleting their cats and such lol

[TheMechanic]

Right? Im shocked people come on here asking for help deleting their cats and such lol

A lot of swaps with vehicles that did not come with catalysts. So asking for one for your 1967 C10 is not breaking any laws. Nor is tuning for it.

[Life is an Enigma]

The thing that sucks about the 1998-05 S10/ Blazer, GMC, Sonoma/ Jimmy, etc. Is the catalystic setup unlike the 4.3 Silverado that has dual cats one for each bank, the S10 trucks go's two in to one for the exhaust, putting both cats on the same pipe. The pre-cat on the S10 trucks are prone to failure and it will usually take out the second cat when it does fail. I had to replace my cats about every year to year and a half that starts getting expensive. Only mods I had was the K&N cold air intake and hypertech. And after looking at hypertech programming through HP tuners, they only modify the high octane timing curve not by much over stock timing. See picture. So cats delete for track use wasn't to gain power it was to stop wasting money hand over fist on replacing the cats. And yes I even replaced them with the magna high flow direct-fit and that set me back just over $1100 and they still failed after a year and a half. And all data log said everything was all good the fuel trims were all perfect until the loss of power then the PO420.
Hypertech Timing
Screenshot (9).png
My timing mods
Screenshot (31).png


4.3 Silverado
s-l1600.jpg

S10
51n04K5i0KL.jpg

[Vbb1994]

A lot of swaps with vehicles that did not come with catalysts. So asking for one for your 1967 C10 is not breaking any laws. Nor is tuning for it.

Right...... i know how laws work.
However asking for helping deleting emissions devices from your 2000+ whatever like 70% of the "help me delete <this>" is what i was referring to on this forum

[Life is an Enigma]

Right...... i know how laws work.
However asking for helping deleting emissions devices from your 2000+ whatever like 70% of the "help me delete <this>" is what i was referring to on this forum

There's lots of videos out there that show you how to get rid of the kitty cat how to shut down the extra fueling for Kitty cat protection (COT) under engine/fuel/temperature control and how to disable the 420 and 4:30 in engine diag. And if you're running a MAF with 02's just retune then after that, retune idle for you don't smell like a 1967 C10 truck. Rich as hell burning people's eyes out of their head behind you in traffic. Wide band is recommended for retuning for MAF or speed density. You can work around it but it is a royal pain in the back side and takes forever. I don't know how your smog laws are in NC, but here in California even on a smog exempt vehicle like a 1967. If you put a newer motor in the vehicle, the smog equipment that it was equipped with in the car it came out of. Must be there also . There is some exceptions like a crate motor straight from GM that comes with the ECU and there's only minor smog equipment that needs to be added.