Experts- need some serious help - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

Camper · 10-07-2013, 05:45 PM

Ok, my car is doing some wierd crap between 2500-4000 rpm when attempting to throttle through that powerband. It almost feels like im lossing ignition and will buck/stutter really hard. It reacts better if I just stab it when im in that range but still has a stutter. Its almost nonexistant on the dyno due to being wot at an earlier rpm range(2k) and it will just push through.

Tuner has looked at it 3 times and swears there is a mechanical issue as he has added fuel/removed fuel, advanced timing/removed timing etc. I have replaced plugs, plug wires, coils, throttle body(TPS sensor), checked fuel pressure. Im not sure where to go next... I thought maybe it was in the harness, but im throwing no codes. Help!?

attached is a snap shot of whats going on in the datalog. You can see fuel trims going super positive and Knock going through the roof while pulling 4-10 degrees of timing. We have checked everything physical and cant seem to locate anything causing the knock.

one common I noticed going through my log and reviewing every event is that it happens at the 38-41% TPS everytime no matter what gear

Car is on E85 & meth

2SS45th · 10-07-2013, 06:15 PM

Have you checked anything in the fuel system yet? And have you filled up since the issue began?

When I was involved in the import game E85 was the fuel of choice for lots of STi owners, and a bad batch of corn can lead to symptoms very similar to this.

Camper · 10-07-2013, 06:25 PM

Ive dropped the filter and it was clean, have also had my ID2000 injectors cleaned. I have been on about 6-7 full tanks of fuel from 3 different stations.

2SS45th · 10-07-2013, 06:33 PM

Gotcha, I really thought I was on to something there. What plugs are in it?

Camper · 10-07-2013, 06:39 PM

currently BR7ef gapped at .028, previously had TR7ix and did it with them only after head swap/retune.

Motion427 · 10-07-2013, 07:20 PM

Little weird how the map spikes just before you got that big knock

Fluidmachine · 10-07-2013, 07:32 PM

Have you tried replacing/cleaning the MAP/MAF sensors yet?

Camper · 10-07-2013, 07:46 PM

Brand new maf sensor. Was gonna swap the map with a known good one tomorrow.

Fluidmachine · 10-07-2013, 07:51 PM

Quote:

Originally Posted by Camper

Brand new maf sensor. Was gonna swap the map with a known good one tomorrow.

Solid plan. Like motion427 said, that little MAP spike just before the big KR kick-in is slightly iffy-looking. Let us know how that ends up going for you.

2SS45th · 10-07-2013, 08:39 PM

You could also try a warmer plug, if you are mostly just driving the car, try the ZR1 plugs. I had random misfires, car breaking up, coughing, etc. and it went away with the plug change to ZR1s.

realcanuk · 10-07-2013, 11:18 PM

The timing is probably being pulled due to the knock. I don't really get why your AFR stays the same while your going into boost. It looks like it just stays at 12.5 right through that log.

Unreal · 10-07-2013, 11:21 PM

It isn't hooked up is why. Warmer plug would not solve this. It isn't a slight misfire, it is breaking up pretty badly.

realcanuk · 10-07-2013, 11:30 PM

Quote:

Originally Posted by Unreal

It isn't hooked up is why. Warmer plug would not solve this. It isn't a slight misfire, it is breaking up pretty badly.

Why log and look for this issue with no wideband. If its lean it would show the symptoms described. Knock and breaking up.

blake-b · 10-08-2013, 02:08 AM

My car did something similar and it turned out to be a loose passenger head ground... It would just fall on it's face and then pick right back up and buck back and forth.

It doesn't sound like you have the exact symptoms I did but it is something to think about. I replaced plugs and wires in my quest... turned out they were fine.

10-07-2013, 05:45 PM	#1
Camper Banned Drives: 10' 2SS LS3 M6 Join Date: May 2012 Location: Phoenix,AZ Posts: 1,370	Experts- need some serious help Ok, my car is doing some wierd crap between 2500-4000 rpm when attempting to throttle through that powerband. It almost feels like im lossing ignition and will buck/stutter really hard. It reacts better if I just stab it when im in that range but still has a stutter. Its almost nonexistant on the dyno due to being wot at an earlier rpm range(2k) and it will just push through. Tuner has looked at it 3 times and swears there is a mechanical issue as he has added fuel/removed fuel, advanced timing/removed timing etc. I have replaced plugs, plug wires, coils, throttle body(TPS sensor), checked fuel pressure. Im not sure where to go next... I thought maybe it was in the harness, but im throwing no codes. Help!? attached is a snap shot of whats going on in the datalog. You can see fuel trims going super positive and Knock going through the roof while pulling 4-10 degrees of timing. We have checked everything physical and cant seem to locate anything causing the knock. one common I noticed going through my log and reviewing every event is that it happens at the 38-41% TPS everytime no matter what gear Car is on E85 & meth Attached Images

10-07-2013, 06:15 PM	#2
2SS45th Drives: 11 Seconds or Faster Join Date: May 2012 Location: Arvada, Colorado Posts: 2,797 View My Garage	Have you checked anything in the fuel system yet? And have you filled up since the issue began? When I was involved in the import game E85 was the fuel of choice for lots of STi owners, and a bad batch of corn can lead to symptoms very similar to this. __________________ I Ain't About That Stock Life.

10-07-2013, 06:33 PM	#4
2SS45th Drives: 11 Seconds or Faster Join Date: May 2012 Location: Arvada, Colorado Posts: 2,797 View My Garage	Gotcha, I really thought I was on to something there. What plugs are in it? __________________ I Ain't About That Stock Life.

10-07-2013, 08:39 PM	#10
2SS45th Drives: 11 Seconds or Faster Join Date: May 2012 Location: Arvada, Colorado Posts: 2,797 View My Garage	You could also try a warmer plug, if you are mostly just driving the car, try the ZR1 plugs. I had random misfires, car breaking up, coughing, etc. and it went away with the plug change to ZR1s. __________________ I Ain't About That Stock Life.

10-07-2013, 11:18 PM	#11
realcanuk Drives: 2007 Corvette C6 983 RWHP Join Date: Dec 2011 Location: Montreal, Canada Posts: 690	The timing is probably being pulled due to the knock. I don't really get why your AFR stays the same while your going into boost. It looks like it just stays at 12.5 right through that log. __________________ 2007 C6 vert, auto, F55, LT3 LME LS402 , WCCH 245 Heads, Pat G. Custom cam YSI / 3.0 pulley, ARH 1 7/8 headers, NPP Dewitts / dual spals, A&A dual pump fuel system. 3.42 polished gears, hardened shafts, Alky control meth, Cartech line lock, ECS axle loops, Trans brace, 6L80 built by me. ID 1000 injectors, comp rockers, Morel lifters, BT springs, Trend 3/8 pushrods, ATI 10% OD Damper Circle D Triple Disc stall 1009 RWHP @ 7000, 817 RWTQ @ 6000,

10-07-2013, 06:25 PM	#3
Camper Banned Drives: 10' 2SS LS3 M6 Join Date: May 2012 Location: Phoenix,AZ Posts: 1,370	Ive dropped the filter and it was clean, have also had my ID2000 injectors cleaned. I have been on about 6-7 full tanks of fuel from 3 different stations.

10-07-2013, 06:39 PM	#5
Camper Banned Drives: 10' 2SS LS3 M6 Join Date: May 2012 Location: Phoenix,AZ Posts: 1,370	currently BR7ef gapped at .028, previously had TR7ix and did it with them only after head swap/retune.

10-07-2013, 07:20 PM	#6
Motion427 Account Suspended Drives: 2010 2SS/RS Red Jewel L99 Join Date: Jun 2011 Location: NB,Canada Posts: 834	Little weird how the map spikes just before you got that big knock

10-07-2013, 07:32 PM	#7
Fluidmachine Drives: Soon to be - 2010 Camaro SS Join Date: Sep 2013 Location: Saskatoon, Saskatchewan, Canada Posts: 24	Have you tried replacing/cleaning the MAP/MAF sensors yet?

10-07-2013, 07:46 PM	#8
Camper Banned Drives: 10' 2SS LS3 M6 Join Date: May 2012 Location: Phoenix,AZ Posts: 1,370	Brand new maf sensor. Was gonna swap the map with a known good one tomorrow.

10-07-2013, 11:21 PM	#12
Unreal Drives: 2006 Z06 Join Date: Oct 2010 Location: Gilbert, AZ Posts: 5,712	It isn't hooked up is why. Warmer plug would not solve this. It isn't a slight misfire, it is breaking up pretty badly. __________________ Nick Corvette Z06 -1200ish rwhp

10-08-2013, 02:08 AM	#14
blake-b Drives: 2009 ZR1 Join Date: May 2010 Location: KCMO Posts: 3,205	My car did something similar and it turned out to be a loose passenger head ground... It would just fall on it's face and then pick right back up and buck back and forth. It doesn't sound like you have the exact symptoms I did but it is something to think about. I replaced plugs and wires in my quest... turned out they were fine.