Rodinator1234

I finally got to drive my car today for a good amount of time, 70 miles or so. It started off all well and good car ran great. After a couple hard launches and runs my exhaust started coming undone or getting loose and banging under the car. Then it started cutting out at random points when the banging was bad. I assume, that it's pulling timing and causing a miss a random miss?? Is this the right assumption?? It idles fine and when it's on smooth pavement doesn't seem to do it. Also, there is a cross member right behind the trans cross member, it's just a little bent thing that goes under the drive shaft and tourqe arm. I guess it's called the tunnel brace? That's where it's banging. I have tried to clearance it and cut a portion of it off, and spaced it down with washers. Is this bracket necessary? Has anyone removed it?? 97 z28 M6 pacesetter lt y pipe, cc502, scorpion roller rockers, PMC for less tune, energy suspension motor mounts, tranny mount, torque arm mount.

Big Al

iTrader: (1)

My 95 does the same thing, but it does not cut out. The long tube headers set off the knock sensor and I have not tuned it out. I'd check the plug wires and see if they are stuck to the exhaust.

Al 95 Z28

moehorsepower

iTrader: (3)

Any type of "Noise" will alert the PCM to pull timing, Some roller rockers will cause it, banging exhaust ect, How much? depends on how much your tuner modified those parameters. Will it cause it to miss and cutout? No, your power will just be less, When your engine is torquing over, it may be a wire arching against something, this happened to me,

Mystery Bird

iTrader: (7)

I removed that brace a few years ago and replaced it with a driveshaft loop.

Rodinator1234

Thank you all for your replies. I really enjoy this forum and have learned a bunch. I was wrong and right, it's banging the torque arm hard. So I have clearanced the y pipe with a few strategically placed blows and hope this is all behind me. A miss may not be the right way to describe what it was doing when it was banging hard. Maybe a pop back through the throttle body is a better description. It was banging hard, and loosing power, I continued to keep it floored and it would just pop. I hope it's timing. I have over the valve cover wires, and a lt4 module. It's raining here now so I'll have to wait to test it. This car is a fun car for me, my winter project. I really like it though.

greenformula94

All u gotta do is buy a lt4 knock module and throw it in ur ecu, its very easy n cost like 25$ or so

jaycenk

iTrader: (1)

They are not 25 anymore. more like 75 now. GM stopped making them. Prices BLEw the freak up lol.

Big Al

iTrader: (1)

My 95 has the LT4 module and it still gets knocks. The long tubes and burn outs are a deadly combo

Al 95 Z28

Zlow28

iTrader: (11)

same here. Ive got a lt4 KM and i still get knock. A little less but its still noticeable.

greenformula94

I dunno I never had a problem with knock after I put in my lt4 km, well maybe its time for a tune then?

1SWT95Z

So the increased noise from headers will be enough noise to pull timing out? I've often wondered about this. It feels like mine might be pulling out timing especially at 3500-4000. I've only got mid length Pacesetters but I have a stock LT1 KM. Is this a common enough thing that tuners are compesating for it?

Zlow28

iTrader: (11)

yep its a common thing. My computer would pull timing after i installed a gmmg exhaust. The drivetrain was completely stock. So pretty much anything that makes the car louder, is capable of pulling timing including rockers.

greenformula94

I wouldnt say louder, but more vibration rather.

It can be a new catback, headers, new roller rockers, stuff like that....

1SWT95Z

That's good to know because I loaded my tune and it seemed to run great for about 2-3 weeks then seemed to feel like it got lazy at that certain rpm range. Maybe a retune would fix it? A DataMaster scan should record timing increases and decreases correct?

Rodinator1234

I have a LT4 Knock Module already. I paid $87 for it on flea bay free shipping. It was banging pretty hard, and yes what started it is a John Force burn out if front of a friend of mien's house. We are old men, and are easily thrilled. I think when I dumped the clutch and eased on the brake it torqued up the exhaust and banged it hard which started working it loose, I didn't have my cat back on real good as I have discovered. I'll run down my mods. I bought the car in Aug, and have put in the engine. Comp Cam 502, alex parts drop in spring kit, hardened push rods, scorpion roller rockers, LT4 KM, catch can, pacesetter long tube headers and off road y pipe, PMC for less tune, Lingenfelter cold air, new radiator and opti and water pump spark plugs, over the valve cover wires with heat shields, energy suspension motor mounts, tranny mount, and torque arm mount. Hurst shifter, and a Ultimate rear end cover with ARP studs, bilstien shocks all energy suspension bushings, sub frame connectors, shock tower brace, adjustable lower control arms, tubular panhard bar, SS wheels with NT05's. It's a pretty nice car and I really enjoy it. I have read so many post on here, and I know most choose the CC503, but I didn't want any surge, and this cam still surges a bit. Everything is still on the car and working except the air pump and the cats. I'll drive it tomorrow and report back, I welded up the mid pipe tonight and I have installed a couple bumpers if you will it should be squared away.

Rodinator1234

Didn't fix it defiantly missing at about 2500 and 4000. Above 4k seems to pull fine. Exhaust is defiantly not banging now. I'm thinking either opti, or O2's. Not throwing any codes, car seems to run fine till it warms up, but it smells really rich at idle and when it's warm the idle is eratic, when it's cold it idles fine. The opti is new, it's a ebay unit I bought it before I found this site. The O2's are new as well when I put on my new headers, I couldn't get the old 02's out of the old manifolds. I've read many post about 02's crapping out after new headers, but I thought 02's will throw a code? Give me some feed back please.

LT1RAY

iTrader: (21)

Sounds to me like your Engine Coolant Temp Sensor or ECT (located on the water pump). Check the wiring going to the sensor and make sure the plug is not corroded. On Shbox's website he has chart if you want to test your current sensor. If not then just buy a new ECT from your local parts store. Make sure the sensor has two terminals, the sensor with one terminal is for the coolant gauge located on the driver side head. If the sensor tests good, the next step would be your O2's. Start cheap

Link to the chart: http://shbox.com/1/4th_gen_tech2.html

Ray

moehorsepower

iTrader: (3)

O2 will only throw a code if its completely dead, will not detect lazy ones, this you have to see with a scanner. But you describe exactly what a lazy and or bad O2 will do. Fine when its cold in OL but when it warms up and goes into CL runs bad..

Rodinator1234

Thank you for the replies. The saga continues. I'm on to something simply by stupid stance. So tonight I changed the plugs, waste of money they all looked fine, but I changed them anyway. Ohmed the plug wires and checked the condition of all of them, they all checked out ok. Noticed I had a little leak from the coolant overflow hose, cut a little off and put it back on. Put everything back together hooked up a fuel pressure gage, held 40 psi for 10 min. Started the car stayed at 40 psi unhooked the pressure regulator went up to 45. Car sounded good thought got it right? Went for a drive, ran great then when it got to temp went to crap bad, low coolant light came on, pulled back in the shop and coolant is everywhere, I defiantly have a coolant leak that's blowing back on the opti, and causing a miss fire. I just hope I haven't killed the opti. I'm not ruling out the oxygen sensors, I have brand new ceramic coated headers and I could not reuse the old oxygen sensors, I couldn't get them out of the old manifolds so I put in new 02's they still look brand new, I pulled them and blew them off and put them back in. I know new headers will kill 02's. Will post back tomorrow after I address this coolant issue.

Rodinator1234

Coolant over flow has a crack as well, ordered a new one of those.