At WOT you are in open loop no matter what, and above a certain rpm also.. 3500?

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Texlurch - 68 Camaro-LT1 w/Hot Cam, TT & TIC coming soon!
" a little spray never hurt anyone, spank you very much!"
or the old standby:"I came here to race, not sell real estate. You ain't scared, is ya?"

 

Saw this post today. Looks interesting. FYI.
From Dave95Z

Bill

Hi everyone,
After 4 months and losin' a bunch of hair, and trying everything on this board except the OPTI, I changed from AC-Delco platinums, to Autolite 106 standards (gapped .045), (found out my AC's were all gapped diff and anywhere from .055-.065), and put my MAF screen back in (for kicks), and guess what? My yugo killer turned into a Mustang Eater. It runs like silk off idle, and takes WOT al the way to 6700 every time. Now back to Thunder racing for power tuning and I finally get to see what this motor will put out... bout fr**ken time...

Later, Good luck!

 

If all else fails,check the tps(throttle position sensor),can be causing same problems and leaning the motor out at higher rpm's.(Quote from Oneflyn95z28)--07-01-98.Hope this helps.

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93 Formula,98,000mi,cold air,msd 8.5,ngk tr55's,A4 firestone firehawks sz50ep's high flow cat,flowmaster 3 chamber, quakerstate high performance 10-30 ac delco oil filter, 180 thermo,le bellows,tb bypass,gm coil,red with chrome wheels.

 

I know I have no business posting here but after reading 6 pages this is one hell of a problem you got on your hands. I'm gonna check up on this to see what you find out.

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1990 Mercury Sable 3.0
Front Strut Tower Brace
Subframe Connectors

 

well.........i would guess what im gonna tell you guys is both good and bad. im not sure if you guys saw my other post, but i thought my new clutch was f'ing up on me after 200 miles. i mean to me this problem looked and smelled like the clutch......well i took it to the guy that did my clutch and he says he is 100% sure its NOT my clutch, that it is an engine miss/stumble. he should have something for me wednesday in terms of what it is.........here we go again, round two........
brian

 

>>>>>wooooooooohooooooooo<<&l t;<<<<

OMG Brian, grip, Everybody...listen to this ****.

friday after work. i installed a new LT4 knock module in the PCM. and drove the car all weekend and the only time my car did not run like a perfectly tuned bat outofhell.was when the temp gauge gets over 200 degrees!!!!!!!!! it ran good all the way home 25 miles or so and i jumped on it a dozen times or so and had a boner the whole time.. i pulled over just before my house. turned the air on and let the motor climb to 230' and then jumped on it and it missed like a **** at 5100. when engine is under 200 it shifts at about 6000 and rock and rolls.
so im ordering a 160' thermo. manual fan switch. and a new coolant temp sensor ( just incase)

so what do ya think. my old knock module was getting some serious false knock and adding to my heat sensitive problem or what.?

the dealer put a new pcm in the car and no help but in a new pcm you have to install the old knock module. so thats why.????????????

 

I guess you guys can count me in too. I am having stumbles all throughout the RPM range, but I know that these problems are somehow directly related. I replaced my IAC and CTS (coolant temp sensor). Neither of those worked. I have scanmaster and it said both of those were acting up yet it didn't take away the codes once I put the new parts in. Any ideas there? How do you reset computer?

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1985 S-10 LT1
Sanderson Headers
Hooker S-10 V8 Conversion Kit
Comp Cam
Roller Rockers
Ported Heads
Total Seal Rings
Accel 8mm wires
Bosch Platinum Plugs
6 speed tranny
4 inches Lowered
Powdercoated frame

http://lt1s10.home.icq.com

 

i just unplug the - side of the battery. for 20 minutes or so and it works on mine 94 pcm.

probably a stupid question but have you replaced opti yet? my freinds vette had several small misses all the way thrue the rpm range and it was fuel pump? have you checked pressure.

 

So Heath, are you saying your problem has been solved? I have a 160 thermostat currently installed. Major thanks to CANTONRACER for all his help on this!!!

Anyhow, I do not have an LT4 KM or the fan switch yet so if your problem is cured these will be the steps that I follow. Thanks,

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94 Z28 A4 GU5
Currently in the shop
TransGo Shift Kit

 

i had the same stumble but i got lucky w/ the opti!!! i wish the best for you all
the stumble i guess is usualy cause by an ignition problem or so ive been told so id trace back every thing, and on a side note can i just buy a LT4 KM from my local auto parts store???? thanx and good luck!!!

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97' SS vert,white on white,leather,M6, 160stat, 3inch catback, taylor wires, bosch platinum plus 4 plugs, underdriven pullys, holly airfoil, K&N, centerforce dual friction clutch,
ported MAF ends, blocked resonator tube
comming soon: 4.10's, headers, vortech elbow

 

my problem will be cured if i can keep it under 200'

the lt4 km made a hell of a diff.

 

Maybe your rev limiter is set too low.

 

i wish it was as easy as a low rev limiter, but it did it with my OBD2 cpu and OBD1 cpu, and the OBD1 saw 6k on the dyno a few times so i can eliminate the limiter....
brian

 

Well, I may have solved half of my problems. I opened the hood and started snooping around the headers, and there it was, my spark plug wire melted against it. It was arcing badly!! So I zip tied it up to the plug boot above, and I am going tomorrow to get some over the valve cover wires so I don't do this crap again!!

I don't think it is going to be the same for you guys since yours is only over 5K, but maybe! The more load you have on the engine, the more spark is traveling through the wires, therefore more of a chance to arc to something. Bad thing is, you can't just rev it up to 5K in your garage and have that much load on it. You would need to be on the road with real "load." Maybe put it on a dyno in the dark, rev it to 5k and watch for fireworks? Hey, it is only $50 to $75 bucks to dyno, and I know you guys have spent more than that on parts to fix this crap.

Or, you could just try some new plugs and wires that go over the valve covers like I am going to do.

Adam

 

All right guys..... i have been watching and waiting for a resolution on this. i have the same 4800rpm to 5100rpm fall off as listed above. We know not all have this problem, it is probably a self inflicted problem with one of our mods...... like maybe roller rockers, headers etc. creating false knock? SVO injectors? poor battery power and ground for current load conditions? do we want to list all of our mods to see any likenesses? i am in the process of redoing/replacing everything that hasnt been done yet plus some..... i am sick of not knowing.
i have
93 Z28 M6 3.23 ratio soon 3.73's
AFR 190 heads stock 1.45 OD afr springs?
stock intake
cc 7.250 pushrods
crane gold 1.5's
cc305 cam
aeromotive fuel regulator
ed wright chip
taylor wires
delco plugs
stock knock sensor (NO desensitizing)
asm headers
high flow cat
borla cat back
24lb SVO injectors
255lph fuel pump
new opti
stereo amplifier (500W)
maybe more?
any similar??

Rob