LT1 Puzzler
05-20-2014, 09:10 PM
#1
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LT1 Puzzler OK so i installed headers about a week ago and everything has been fine till a couple days ago [5/18/14]. on the way home from work the car stalled out in an intersection, which was super awesome 
. i had it towed home. today i checked fuel pressure and the regulator. regulator is good. fuel pressure is 40psi key on engine off - 44ish with the regulator vacuum hose pulled at idle - and 36 at idle. i have a new fuel filter ready to go in if need be. the problem is that sometimes the car starts misfiring (and in my case stalls out) out of nowhere once it reaches operating temp. but it seems intermittent. the plugs(acdelco) and wires were replaced and zip tied out of the way when i put in the headers, and i checked them again today - no fouling. i'm stumped, any insight would be much appreciated. i just want to drive my car again 
please and thank you
. i had it towed home. today i checked fuel pressure and the regulator. regulator is good. fuel pressure is 40psi key on engine off - 44ish with the regulator vacuum hose pulled at idle - and 36 at idle. i have a new fuel filter ready to go in if need be. the problem is that sometimes the car starts misfiring (and in my case stalls out) out of nowhere once it reaches operating temp. but it seems intermittent. the plugs(acdelco) and wires were replaced and zip tied out of the way when i put in the headers, and i checked them again today - no fouling. i'm stumped, any insight would be much appreciated. i just want to drive my car again please and thank you
05-20-2014, 11:45 PM
#2
Did you replace the o2 censors when you installed the headers? These are usually the source of problems during/after header swaps when
A). The original part is reused but somehow damaged
B). The original part is replaced with a crappy autoparts store brand censor
C). Wiring extensions (for longtube headers) are somehow damaged, dirty, not functioning properly somehow.
Just some things to think about. Usually problems aren't "coincidental" after a modification (your header install likely didn't damage an injector, FPR, and it probably didn't just "happen" coincidentally after a modification)
I've never had an issue personally, but based on others posts the o2 censors can be quite finicky/sensitive.
A). The original part is reused but somehow damaged
B). The original part is replaced with a crappy autoparts store brand censor
C). Wiring extensions (for longtube headers) are somehow damaged, dirty, not functioning properly somehow.
Just some things to think about. Usually problems aren't "coincidental" after a modification (your header install likely didn't damage an injector, FPR, and it probably didn't just "happen" coincidentally after a modification)
I've never had an issue personally, but based on others posts the o2 censors can be quite finicky/sensitive.
05-21-2014, 08:06 AM
#3
My $0.02... ...the problem is that sometimes the car starts misfiring (and in my case stalls out) out of nowhere once it reaches operating temp, but it seems intermittent. The plugs (acdelco) and wires were replaced and zip tied out of the way when I put in the headers, and I checked them again today - no fouling. I'm stumped. Any insight would be much appreciated. I just want to drive my car again
Hot = Issues
If that is the case, the problem may not be directly related to the header install; it could be your Ignition Control Module (ICM), located near your coil, once heat-soaked, is failing.
I could be wrong (maybe someone else can chime in), but I don't think that particular part can be tested at Autozone/Advance/<insert the name of your favorite local auto parts store here>/NAPA/etc... ; so you can replace it or (easier / cheaper still) try the washer spacer mod first (i.e. - adding a washer between the head and the ICM mounting bolts) and see if that helps / resolves your issue.
Maybe (and this is just a guess on my part) the headers have allowed too much heat under the hood, and that extra heat is slowly cooking your ICM.
Good luck and keep us informed of what you find.
: )
05-21-2014, 06:10 PM
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Are we talking up to temp as in thermostat open temperature, or are we talking closed loop operation? Open loop, no O2 sensor input, closed loop, O2 sensor input. Also, wires replaced? Have you checked them for arcing? Some of the supposed good wires have the worst track record for arcing put of the box...
05-21-2014, 08:35 PM
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replaced the fuel filter just in case then drove it around about 10 miles. looked under the the hood when i got back (it started misfiring right as i got back) and i found a leaking radiator hose leaking right at the connection to the thermostat. i have replaced the hose and coolant. and now the car won't start. it will crank tho just not fire up... >
Last edited by MedicinalCreamDogs; 05-21-2014 at 09:23 PM.
05-22-2014, 10:24 AM
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replaced the fuel filter just in case then drove it around about 10 miles. looked under the the hood when i got back (it started misfiring right as i got back) and i found a leaking radiator hose leaking right at the connection to the thermostat. i have replaced the hose and coolant. and now the car won't start. it will crank tho just not fire up... >
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05-23-2014, 02:54 PM
#8
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even if it's an unvented opti? maybe i'm just being delusionaly hopeful, sigh.
how would i go about diagnosing an opti? i really don't want to pull that if i don't have to...
update: i don't know if this means anything but i unplugged the ICM and tried to start the car, results were no different than plugged in. same with the coil.
how would i go about diagnosing an opti? i really don't want to pull that if i don't have to...
update: i don't know if this means anything but i unplugged the ICM and tried to start the car, results were no different than plugged in. same with the coil.
05-24-2014, 07:55 AM
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The basic difference between a vented vs non vented opti is on the bottom. If anything the vented is a much preferred option to allow for "venting" of corrosive gasses created from the arcing from the rotor and pins. The seal between the cap and opti body is a tiny seal and combine that with the heat from being connected directly to the front of the engine, its easy to see why its not great. Residual coolant from bleeding, water from washing, and oil from leaks easily ends up inside there. If you had a leaking coolant hose directly above....
Do a search on diagnosing the opti and you'll locate a few methods in doing so, also remember they opti often fails intermittently and with varying degrees of severity. Can be frustrating. PM me if interested in a eBay opti that was know good when I removed it for my 24x conversion. Cheap option.
Do a search on diagnosing the opti and you'll locate a few methods in doing so, also remember they opti often fails intermittently and with varying degrees of severity. Can be frustrating. PM me if interested in a eBay opti that was know good when I removed it for my 24x conversion. Cheap option.
06-03-2014, 07:28 PM
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Ok so i went about testing and found the coil and icm to be bad(injector pulse was good). So i replaced those and the car started right up! ...but ran really rough. Like it had a HUGE cam in it - Blowing black smoke out the back, all that good stuff. Would this be because of the fuel left in the cylinders from the times it was cranked? It runs smooth above 1100 rpms or so, what's next guys?
edit: it's not black smoke like a diesel, more like running super rich.
edit: it's not black smoke like a diesel, more like running super rich.
Last edited by MedicinalCreamDogs; 06-03-2014 at 07:35 PM.
06-04-2014, 08:27 PM
#12
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I think i'll put the money I would've spent on a tester toward a new opti. AC Delco the best choice? i know it costs lots of moneys. i've read some things about the sensors not being cool in other-than-AC-Delco opti's. Thanks for all the assists guys I love you(s)! 
06-04-2014, 10:34 PM
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I think i'll put the money I would've spent on a tester toward a new opti. AC Delco the best choice? i know it costs lots of moneys. i've read some things about the sensors not being cool in other-than-AC-Delco opti's. Thanks for all the assists guys I love you(s)!
