my backfiring problem...

sounds like a plan, i think i'm going to try the chandler motorsports cap and rotor since they have a 1 year warranty on it, and nick chandler said he's never had one come back, so that sounds good to me. do you have any links for cleaning the opti? i've found a little about it, but nothing great...looks like i just need to pull it apart (carefully) and shoot some isopropyl alcohol on it (not on the sensor though right?) let it dry out, then reassemble?

Yes, you need to inspect and clean the optical sensor and the transmissive disk. If it is only dusted with dirt I would use cotton swabs dipped in alcohol......

pulled the old opti off last night...epic, catastrophic rotor failure....chunks and slivers of plastic EVERYWHERE inside the cap...glad i picked up that used one from robbie!

PICTURES!

as you wish

[You must be registered and logged in to see this image.]

WhAA!!!

And it ran like that? Wow.

DAYUM! Holy Opticrap Batman....

more like it stopped running like that lol

Doesnt quite explain the blue smoke though.

well, the smoke may have only appeared blue because of the camera...if you listen to the video one more time, toward the end when i was revving the engine, you will be able to hear a nasty miss, where the engine actually bogs. i believe i had a missfire the whole time, and that was causing a lot of the smoke. I also pulled the intake manifold yesterday, and discovered a lot of oil where oil should not be, so i think some of my problem may have come from oil leaking past the intake manifold gaskets and getting sucked into the cylinders...possibility?

WOW

just wanted to follow up on this. I pulled the motor and completely resealed it (minus the headgaskets) and installed a gm opti with a new cap and rotor, and this opti i sealed around the outside at the joints with black rtv. I also painted the engine bay in the process, satin black. The results: the backfire is 99 percent gone, it no longer backfires when i release the accelerator, and then push on it again. The one thing i haven't fixed yet is my "tip in" problem with my BBK 58mm throttle body. I'm pretty sure the damn thing is just too big, and the car hasn't had a proper tune yet, so it bogs a bit if i push the accelerator too fast...like it's trying to trick me, then the revs come up hard.

I've read that it's probably the computer sending a super lean signal when the throttle blades are moved too quickly (not even to wide open). If anyone locally has LT1 tuning software, i'll buy you a case of beer! I've learned to live with it for now, i might try fiddling (with a voltmeter) with the TPS to see if it's just a little too far closed (idle dips low every once in a while), which might contribute to my problem...and i'll check 02's just in case

ps, threw in a couple of pictures from the recent snow!

[You must be registered and logged in to see this image.]

Thats a good lookin engine. I've always thought the LT's looked better than the LS.

Do you have a VSS? Not having one can contribute to odd engine behaviour around idle and tip-in...

huh...never thought about that. I don't have one...do you really think it could cause this much of a noticeable problem?

bluehellfire666 wrote:huh...never thought about that. I don't have one...do you really think it could cause this much of a noticeable problem?

In my case not having the VSS has caused idle issues, stalling when coming to a stop or going to neutral when moving, and some driveability issues from a standstill.
One could suppose that a larger TB, no tune, and the lack of a VSS could combine to cause this issue.
A quick search...
[You must be registered and logged in to see this link.]


Also, have you checked for intake leaks??

i just completely resealed the whole motor, and went over the intake system for leaks with a pretty fine toothed comb. I'll take a look around tomorrow to see if i can spot anything blatantly obvious, but the way that it runs i don't think i have any vacuum problems. I don't have any problems with going to neutral or clutch in, or stopping with the idle...drops right back to where it's supposed to be 99.9 percent of the time. Occasionally it will idle a little bit low, but often corrects itself or i start moving again before it has a chance to correct itself.

It also does this odd thing when it goes from closed loop to open loop (or whatever way it goes when the computer starts using the O2's). If i let it warm up, which i do almost always, it will try to lower the idle a little bit, and will go too low, then the computer will compensate and rev up to about 1500 rpm, then the idle will drop to maybe 500 or so (way low) and then rev up again...but it'll never stall. It'll cycle like this a few times then the idle will settle in very nicely and the car will run beautifully, except for that damned hesitation.

Important fact, the hesitation isn't just from idle, if i hold the throttle at 2000 rpm, and open it quickly it will bog and hesitate hard...not a lack of spark hesitate, i know what that feels like. It will do this at almost every rpm at almost every time.

Go get it tuned! Or put a stock TB back on it and see what happens, I bet your Issues will go away.

okay, just ran out and swapped out the throttle body for a stocker...didn't fix it, but it seemed to have helped with my powerband. If i nail the throttle above (an estimated) 3000-3500 rpm, no hesitation and no miss and she goes like stink. If i blip or nail the throttle below those rpm's the engine tries to stall and seems to miss, then picks up, but not super quick. If i accelerate smoothly, but still very quickly, i will occasionally feel, but often not hear, a little bit of a miss of some sort (kind of a little bump in the core of the car). If I accelerate smoothly but not quite as quickly, up to WOT, no misses, no hiccups, just hard pulling to the moon.

List of recent parts:
Used GM Opti, thoroughly cleaned with alcohol and sealed up with a new cap and rotor
New MSD plug wires separated using plug wire holders every 6-8 inches to prevent ANY arching
New Ignition Coil
New Ignition Control Module
New Spark Plugs, gap checked on all ~6-8 months ago (very few miles on them, just lots of time)
New Coolant Temp Sensor
New intake seals all around, no vacuum leaks as far as i can tell
Less than one year old O2 sensors
Got a fresh PCM and had it mail order tuned, properly this time with No emissions.
Running a LS1 MAF

Could intake tubing size be part of my problem? Right now i have 4 inch tubing...it is larger than the MAF, but the MAF is in front of all of the tubing, so there shouldn't be any problems right?

edit: just had a thought...could i be collapsing a lifter? They're the stockers.

What push rods are you using?
Could be push rod flex if they are stockers.
What injectors are you using?
If they are stock you may have one that is shorting internally, or could be dirty.
GET A TUNER ON IT! They can look at everything and see what is going on.

push rods and injectors are both stock.

When you say get a tuner on it, do you mean do a dyno tune day? or should i invest in a LT1 tuning software? I'm super short on cash right now (i'll show you my bank account balance to bring that point home), i guess that is the life of a college student...i think i need a part time job!

I'd personally really like to get tuning software and tinker with it for a while to see if i could figure everything out. Something like LT1 edit or the likes...it's too bad i didn't go LS back in the day, i could've had a lot easier time with all this crap!

Is it better or worse as the ambient temps change? In other words is the problem more noticeable when it's hot outside? Does it get better when it's cold? It sounds like a tip in enrichment problem. If it was a carburated engine it would be discribed as the accelerator pump function. It sounds like you're not getting enough gas on throttle tip in. The leaness will cause popping. Download a free copy of Datamaster and do some data logging. It will show up. It's tuneable.

Take it to a professional tuner, Don't try it yourself unless you plan to spend some money on parts! There is a reason professionals get paid what they do. One minor blip in a map,which there are quite a few that the motor uses, can screw up parts fast! With a situation like yours , it's not a newbie tuner fix. Save your money, don't drive it unless you have an AR gauge, and get it fixed. If you are running lean, reason for the AR gauge, you will screw some stuff up

Megasquirt 3? Cheaper than a stock opti and you can have all kinds more fun.

Sorry, but a little Hyjacking here,,,,,,

Adam7e, How much of a pain was it to install the megasquirt? Is it user friendly? Did you eleminate the opti and go with something different? If so can you start a tread about it/your bulid?