I finally fixed my problem. I actually stumbled on to it today while replacing my waterpump. The pump started leaking on Friday, I figured since the opti-spark and plug wires were only two months old, I better do so before the water/coolant leaked into the components. While I was removing all the parts out of the way to include the pump, I noticed the #3 wire was very close to the idler pulley. I pulled the wire back and saw it was either barely connected or not connected at all to the opti. The inside boot was corroded. Additionally, the wire was almost cut in half. Apparently the wire was lying on the idler pulley. The pulley cut down to the spiral core. After replacing the water pump and wires, I took the car out. Each time the car ripped through 1st, 2nd, and 3rd gear. No missing, breaking up, or backfiring. The car pulls cleanly to 6000 rpm. Just yesterday, anything above 4500 rpm the car would backfire (still rev to 5000 rpm) then totally drop on power. Anyway, the wire was definitely the cause. I even checked the car in the garage at night to see if any of the wires were arcing. I checked gap (.050) and visaully checked all wires two weeks ago. The car idled smoothly and still had decent pwoer. I obviously missed the # 3wire. I guess the pump failing was a blessing in disguise. I wish everyone luck in finding their problem. I suggest looking at the wires carefully. Again, my wires were only two months old. Thanks to everyone for the help.

 

Friggin' AWESOME! It's nice to hear that someone has finally solved the missing problem. I would have to say wires are going to the top of the chart for the leading cause. It's funny how these problems usually occur after a recent plugs/wires change. Thank you for posting your results.

 

awesome. Guess i'll have to check out the wires.

 

I HAD THE PULLEY HITTING THE WIRE PROBLEM ALSO!

i found it when i was pulling the rt side head off! i actually made a peice of aluminum and put it on the stud and bent it over the wires to hold them into position so they would not hit the pulley after they relax! i went from delco to msd back to delco so i know wires are not my problem allthough once i get the new jethot LT's im going over the VC's with the wires so its easier to moniter and looks better!

lt1 edit and maft this sunday! weather pending!

 

well I just took her out tonight to get a soda, and on the way back it hard started to warm up (but still cold, around 140-160) and I opened it up and it revved all the way up and shifted hard. Music to my ears... haven't heard that sound in a while so I guess its time to install a manual fan switch and 160* stat and i'm doin wires pretty quick, so hopefully i'll never have to worry about this again

 

hope it stays that way for ya! i have a 160 stat and pcmforless tune and it stays nice and cool but i still have it.......guage hasnt been over 1/4 in a long time. oh well, like i said, springs i think are the culprit, so i ordered some, well.......they came with my nitrous cam, and complete valvetrain! i have a new opti going in also. oh wait, im broke and cant afford to install it.....shooting for freakin may, maybe even june at this rate........
brian

 

yea I know how that is man. i cant afford to take any blind guesses

 

sold mine! but i know the guy! so if anything new comes up in the diagnostic nightmare i told him ill look at it!

hes not a hot rod fan anyway! an occasional burn out or two but it will probably never see hard driving!!

good luck guys

 

you sold your car over this??
brian

 

I have had the dreaded miss for some time now. I know I have a few things that need done to eliminate them from the possiblities. Anyone know what the plug gap to run on a supercharged set-up is. Also what is a good starting point for the fuel pressure - it is around 40psi currently. I have an MSD 6BTM i will be installing sometime this week (I hope) and have already installed an msd coil. It seems that there has not been any one major problem that has solved the issue for everybody. Like everyone else the problem is more noticable the hotter it gets and the bigger gear number i am in. It seems almost like a rev limiter that you can still accelerate with, but slowly.

Another problem i have is it runs good (except the high rpm thing) when it is cold, but as soon as it warms up (about 10-15 miles - depending on air temp) it starts loading up extremely bad like it is a stuck float in a carbed engine. It starts stinking of gas and blowing black smoke terrible (you wouldn't want to be a smoker and stand behind the car) and the fuel mileage is terrible (around 200 miles or less to the tank). Any Ideas before i take it into the Specialilty Shop?

Here is what i have

95Z Cnvt w/ 80000 miles


96 LT4 (from Grans Sport Vette) unknown internals
assumed to be stock, w/ 36000 miles
No Egr (standard for this LT4 engine)
No Smog-Pump (also standard for the LT4)

Mufflex Y pipe into 4 inch single into Spin-Tech dual 3 inch out
No Frigging ground clearance

Hooker LT w/ o2's installed and o2 harness extensions
No cats
High FLow Thermostat (180-degree)
52mm BBK tb
Adjustable Fuel Regulator
255 LPH plug and play pump with full 12 volt power
50lb injectors
ATI 9lb single intercooler Supercharger
Stock MAF with ATI MAF massager (no clue what this does)
Stock LT4 plug wires
ATI reccommended plugs (AC, i dont remember which ones)
Fastchip programming (Ed Wright)
96 LT4 Knock Module (if this the module that is on the PCM)
96 LT4 Knock Sensor (someone told me this is the worng one
and will set off a code - which it has - i intend to replace it
this week as well. One of the engines had two sensors and
the other had only one - I think the LT4 had two sensors
and we only plugged in the one like it was on the camaro)

Mccleoud Street-Twin clutch (this thing is way too grabby, any
recommendations - it seems to be off or on and right off of
the floor)

Completely stock suspension and brakes (someday i'll put some
good brakes and susupension parts on)

MSD - 6BTM (where in the heck have you guys been mounting
these things?)

Grooved crank hub (keyed)
Stock wheels and BFG Comp TA's in stock 245 size.
Fuel pressure and Boost/Vacuum Guages (autometer)
Stock OptiSpark - but the 96 engine had an extra plug in for the
sensor on the crank - we just left this unused.

I'm sure i forgot a trinket or two but this thing is really bugging me. Thanks in Advance-

 

I know this is a very old thread, but just wondering if many of the 50+ people ever figured out their problem. Mine has the same stubbling for the past year now. One question I have is at the miss (5100rpm) is your car blowing out black smoke?

 

I have no black smoke..........still have the miss. I'm guessing its either fuel or bad springs for my car. Won't know until March when I do heads/cam/n2o..........By that time I doubt (unless its REAL obvious) what was causing this......
Brian

 

Mine was blowing black smoke when it was missing and cutting out.

NO MORE!!!!!

I did a bunch of changes at one time so i can't definetively say what one thing fixed it.

I hooked up the MSD BTM unit (except for the vacuum hose to retard the timing (still waiting to finish it)), replaced the plugs with 2 degree's colder plugs and a considerably smaller gap, put in the correct year knock sensor, and replaced the o2's which were damaged.

I think the main thing was the plugs, gap and the fresh o2's.

I surprised a guy on his newer yellow sportbike (zx6 or cbr6??). As he pulled out to pass me, i downshifted to second at about 55 and broke the tires loose. He already had speed on me so he passed and I wipped in behind him to pass the wife which was in the Surburban in front of me (on our way home). I didn't lose any more ground but he was already a good 5 or 6 bike lengths out. I passed him at 140mph after riding his *** for a bit as i pulled up on him. I'm guessing this is a low 11 second ride maybe high 10's now. It is way quicker (after getting traction) than my tubbed 11.50 68 Chevelle SS is.

Now the only problem i have is massive traction loss in first and second gear. Well, i do have some abs codes and the brakes are way soft. I am getting them fixed now and will be charging the ac as well since i unhooked it to install the engine.

Later,
Sean and Sherry Morley
Kansas Chapter Rep - Welcome to the VMOA!
Member Number #1479
Our Website - Morley's MuscleCars and MuscleBikes

 

I'm in the same boat as Sean........doing heads, cam, springs, fuel pump, plugs, wires, opti, etc in one big bang will probably fix my problem. Thats all that I can say. As mentioned, I've redone my whole ignition already and its still happening, so I'm lead to believe that it is fuel or valve float, both of which are possible with 83k miles. I'm good about my maintenance also, and I've done all of that on top of redoing my ignition.........
Brian

 

So no one has really pin pointed the problem then yet, except for the few with problems with plug wires.

I myself have installed a new Waloro 255 lph fuel pump so the fuel pressure is good, opti spark, and just replaced the coil and still no fix, also the wires checked out good when I first experienced problems with the opti spark. Now what, I'm tired of spending money on this. I haven't replaced the coil wire yet, but that's next.