backfiring/stammering below 1700 rpms wtf?
#1
backfiring/stammering below 1700 rpms wtf?
my LTFT's are within 2% at any given time (SD mode). i've messed with the timing manually also, but the car has no ***** below 1700RPM's and backfires/stammers when i throttle up with the TCC locked.
zero KR
i'm running a stock LS6 timing table right now.
setup:
2002 OS
LQ4
823 heads with .040 head gaskets (.035 quench and 10.2:1?)
226/231 .598.601 on a 114
LT's and 3" X-pipe
FAST 39# injectors
TR-6's. i cleaned them and re-gapped at .040 from .060 with minimal effect
running a catch can, so the plugs are bone dry.
zero KR
i'm running a stock LS6 timing table right now.
setup:
2002 OS
LQ4
823 heads with .040 head gaskets (.035 quench and 10.2:1?)
226/231 .598.601 on a 114
LT's and 3" X-pipe
FAST 39# injectors
TR-6's. i cleaned them and re-gapped at .040 from .060 with minimal effect
running a catch can, so the plugs are bone dry.
Last edited by rumblebox; 05-22-2013 at 10:11 AM.
#3
As in, it will barely accelerate. This cam is way too small to be this gutless below 2k..... especially since i've had way bigger cams in this same engine with more off-idle torque than this.
Maybe if i were running a 260@.50 cam in a 4.8. lol
It idles smoothly at 800rpms and pulls 10# of vacuum with the AC on. It also has a KILLER midrange pull all the way up to 6500.
Maybe if i were running a 260@.50 cam in a 4.8. lol
It idles smoothly at 800rpms and pulls 10# of vacuum with the AC on. It also has a KILLER midrange pull all the way up to 6500.
Last edited by rumblebox; 05-22-2013 at 04:45 PM.
#4
Keep in mind you have a 3500 stall with a 114 LSA cam. It wont very peppy under 1800 RPM unless you goose the throttle a bit. Does it always sputter and backfire? How does it idle?
#5
LS1TECH & Trucks Sponsor
iTrader: (34)
Can I ask why you're locking the converter and accelerating with it locked at such low rpm?
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#9
I have a much bigger cam with an a4 as well. I have a extremely tight fti 3000 stall. I have 3.27's so my car lugs around. I agree the stumbling is an issue that needs to be addressed, but part throttle and wot your rpms should jump up above 2k at the bare minimum. I've never his the gas and had the car start accelerating at such a low rpm.
Curious about going with a hotter plug as well. I run tr6's with a .032 gap for nitrous but wont be spraying it for a while. A cold plug is nice to have though.
Edit: just read you have the tcc locked, why? No reason to accelerate from that low of an rpm when you could just give it some gas and have the car downshift in my op.
Curious about going with a hotter plug as well. I run tr6's with a .032 gap for nitrous but wont be spraying it for a while. A cold plug is nice to have though.
Edit: just read you have the tcc locked, why? No reason to accelerate from that low of an rpm when you could just give it some gas and have the car downshift in my op.
#10
In bumper to bumper traffic with a 3500 stall(even a tight one like this), it's nice to keep the verter locked with tad more throttle instead of downshifting constantly. I have it set to unlock at about 50% throttle.
I tuned it to lock when i hold it in 3rd for slow traffic also.
With all my prior setups(more radical), it had enough torque to keep the TCC locked all the way down to 1200rpm's in traffic with no lugging or stammering issues.
The main difference between this setup and the old setup are the LS3 heads(vs 317's) and higher compression/tight quench..... I knew I'd lose a little bit of torque down low with bigger heads, but i thought this cam would make up for it.
EDIT: i advanced the timing at low RPM's under heavy load to 1*/100rpm's. I'll flash that tonight and see how it does. I'll also see if i can get the trims a tad bit closer to zero.
I tuned it to lock when i hold it in 3rd for slow traffic also.
With all my prior setups(more radical), it had enough torque to keep the TCC locked all the way down to 1200rpm's in traffic with no lugging or stammering issues.
The main difference between this setup and the old setup are the LS3 heads(vs 317's) and higher compression/tight quench..... I knew I'd lose a little bit of torque down low with bigger heads, but i thought this cam would make up for it.
EDIT: i advanced the timing at low RPM's under heavy load to 1*/100rpm's. I'll flash that tonight and see how it does. I'll also see if i can get the trims a tad bit closer to zero.
Last edited by rumblebox; 05-23-2013 at 09:36 AM.
#11
TECH Enthusiast
iTrader: (1)
IIRC the TR6 is colder than stock and at lower rpm and lower loads the engine is producing less combustion pressure and heat than a stock engine would. I would venture to guess that the spark is breaking down a little bit in these areas.
I had a similar situation one time when I swapped out plugs to run nitrous then forgot to swap back. Then I tuned for hours trying to get rid of what looked like a lean stumble. Kept adding fuel and adding fuel and it didn't get any better. Changed the plugs and viola, no stumble but then it was rich, had to take fuel back out.
Might give it a try, it's cheap and easy.
I had a similar situation one time when I swapped out plugs to run nitrous then forgot to swap back. Then I tuned for hours trying to get rid of what looked like a lean stumble. Kept adding fuel and adding fuel and it didn't get any better. Changed the plugs and viola, no stumble but then it was rich, had to take fuel back out.
Might give it a try, it's cheap and easy.
#12
^^ Good story lol, sucks you had to go through all that. My tc unlocks with 40% throttle. I can cruise at 1200 rpms and never bucks or surges. 232/239 .617/.624. Which my car has gears though.