went to track saturday and only ran best of 14.2 but icant keep it cool enough normal cruising its at 170' sitting in lanes and burnout box it would crawl up to 230 real quick. ill install a fan this week to help[ that 160 stat out. it only missed three times all weekend and all three at track when boiling hot. it was humid as hell
other than being at track it has ran strong all week long. i think i might be good to go if i can keep it cool enough. who has the best link for cooling fan switch install.
oh yeah one of the guys from mofba.com is going to scan and program it for me the week after labor day.

 

Kewl. Wish that I could find someone in the Akron/Canton/Cleveland area that could program my fans to come on earlier. I've installed the 160 but really need to do the fan switch in order for the T-stat to really do it's job. Glad to hear that it seems to be working out for you. I need to get on the ball and start looking for my problems.

 

ok, 2 things to address:
1) a torque arm stock connects at the rear the tranny (tailshaft) and runs to the rear, runs right next to the driveshaft and deals with torque transfer/traction. upgrading to an aftermarket one (BEEFY, LOL) allows for better transfer and more traction, hence cutting 60 ft times and 1/4 mile times in the process. a drive shaft loop is a loop that goes around the driveshaft that catches it if it breaks, instead of impaling your car. its mandatory at a lot of tracks if your car is running like 13.99 or better.
2) www.pcmforless.com.........get a tune and a 160 stat and you will be in cold heaven with me, with my temp guage NEVER getting higher than 1/4 after bryans tune. its cheaper and better then anyone else. i opted for an obd1 tune since there is 5-7 rwhp more for whatever reason over an OBD2 tune.....
will report back tonight!
brian

 

well, progress was made but the gremlin persists. car runs much better after plugs/wires. however, the miss was still present at ~5400 in 3rd gear, though not as prevalent. im beginning to feel like its fuel related.....car seems to idle and drive fine, just chokes a lil up high. also, got my torque arm in and its great! did everything it was advertised to do, except that its vibrating up against my exhaust, so that sucks. at least i got the Z back....if i come across anything ill post...
brian

 

Brian,
I have had the same exact problem since modifying my LT1 to a 396 stroker. The stumble occurs at 5100rpm, and is worse with increased hp. Part throttle, no problem. I have been chasing this for two years and 30000 miles. It has never had this problem on the shop dyno out of the car. That rules out mechanical stuff. Sure is frustrating, but am determined to find it.

Alan

 

If you havent replaced the coil, I recommend replacing it because thats what fixed mine! 5,300 rpm miss.

 

OMG!!! back from the grave!! FWIW i still have it, and the thought being if its ignition i may have gotten a bum opti from GM. so i have another, that 100% works with 5k miles on it so if the miss goes away it was a bum opti. if not, it is most likely fuel related or some other gremlin. if i can figure it out your damn well assured ill be posting back...
brian

 

mines only did it once in the last month,, i do have a lt1 scanmaster data file on it if anyone wants to read it , i can mail it to them we recorded a 1/4 mile pass on it and you can see the right side is going really lean when it misses. lt side 750?mv's?
and the rt side like 53?mv's? don t ask me I have no idea but now that its cool it runs damn good... the problem isnt fixed but just temporarely gone (like summer),,

next up STB,SFC, vig 2800 TC, and Hooker LT's for the winter project. look out!

any one else killed this gremlin yet , hey Brian?

 

i have an opti with 5k miles on it that was working perfect waiting to be installed, other than that i still have it. eventually ill get it in, and hopefully thats it. i HEARD that GM had a recall on a bad batch of optis around the time i bought mine, so maybe thats the problem. if not, i dunno what im gonna do.
brian

 

I would go with timing...although I have an A4 with similar probs...my fix was all ignition (wires,coil etc.).....slap some 1.6s on there and see what it does...I have seen some guys here have problems like yours....but after they did some mods it was fixed....and the 4 people who had the prob. all had 1.6s as a mod...so who knows....just a thought.

 

TTT im back, and i was with the club yesterday and We Dynoed the cars! I dynoed mine 3 pulls, and the Air/Fuel ratio is all jacked up WHY?????? but im at 15.5-16 on the graph all the way through my pull !!! i should be at 12 or so! so im running dangerously lean??? im doing LT1 edit in a few weeks so hopefully it will change that and Possibly this might have something to do with my high rpm miss!


hows it goping guys anybody kill this RAT yet???

TTT

 

i heard GM had a batch of bad optis go out. at any rate, if it is the opti you have a 12 month 12k warranty anyways.....thats my thing to try this spring....
brian

 

I have been following the threads from everyone with the same problem. I recently purchased a 95 M6 LT1 only to have the motor spin a bearing with 100,000 miles. Unfortuantely, I could only afford a used long block 60,000 miles on it. Anyway, to make long story short, prior to receiving the car back, I replaced the plugs with denso iridium's, taylor wires, new opti-spark, fuel filter, coil, ignitor, seafoamed the motor, flushed the injectors, flush the fuel lines from the tank forward, and the list goes on. Immediately, I noticed popping (back fire) from the used motor, missing and so on from 5100 rpm's on up. Some days it's not there. In any case, when the motor is cold it pulls like mad. I have asked around and the consensus is valve springs. It appears when the motor heats up, the metal springs become soft, thus are not able to control the high rpm valve events. The cost $350.00 in labor only. The motor before (one that died) did not have this problem. I also noticed this problem occurs on mostly high mileage LT1's. One last note, I checked the valve lash on the used recently installed motor and removed some of the tension (at least one full turn on each rocker). The motor liked it and felt better. The miss is not so bad now. 50/50. I am going with the valve springs. I have to say, with the money I paid for the car and repairs that I extremely disappointed with the car.

 

my original miss occurred after a bunch of 6k dyno pulls.......thought it was opti, and it was. BUT, i put in a NEW opti and it was still there. i think springs may be the problem, and that the new opti might have been bad from the get go. im getting a cam and valvetrain and have a used opti that was working 100% and has 5000 miles on it. while i probably wont have it all installed until march i will be sure to post back if it goes away. best of luck to all, and to the newbie (lol) dont get discouraged, the car is really worth it and unfortunately what you are going through is common, but also fixable.
brian

 

First time posting on this thread and unfortunately I'm in the EXACT same boat as the rest of you...

I can't even begin to tell you the number of things I've fixed/replaced on my 25th in the last 2 years... the car ran well until about 3 weeks after I bought it and it's been a constant problem since...

FINALLY last summer I got it running right with the exception of this high RPM missing... had a couple more bumps in the road along the way... but it was and is my only constant problem.

Heath, I know this is 6 months late... but I used to have the EXACT SAME problem with the RPMs around 500 or so jumping up and down... it went away for awhile only to come back later with a vengence... it was just like before for a couple of weeks then slowly got worse until it started actually stalling when idling... turned out my CAT was clogged... I cleaned her out and things are back to normal... no more problems idling but my 5000+ RPM "rev limiter" keeps kicking in...

It's barely noticeable in 1st, and gets worse through each gear... finally in 3rd I just let off the gas instead of pushing it...

I'm going to try the LT4 KM like you've done... apparently with low temps it solves the problem...

BTW, my car stays at low temps just fine with my 160 deg. stat... I have the Hypertech Power Programmer III and it let me reset the temp my fans kick in at to compliment the low temp stat... just figured it might be worth a try for the next time you're sitting in the heat at the tracks... I haven't gone over 200 deg in a long time, even when I was sitting at Norwalk Raceway for the Pontiac Nats last August...

It's extremely hard to keep interest in your car when all you can do is worry about what's going to break next or how to repair the problem you're having that seems completely unrepairable... but it's nice to know that I don't have to feel frustrated by myself anymore...