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LT1 stutters under load, breaks up at 5k+

9.3K views 29 replies 10 participants last post by  DMC-4OOEX  
#1 ·
Hey guys.

Over the past month, my car started to break up around 4900rpm and up. When I go to hammer on it, it would pull smooth and then almost act like it's hitting a rev limiter at around that range and slowly work it's way up higher but breaking up and hesitating the whole way.

Just recently, it started breaking up under a load too. When I get around 2000-2500rpm it will start stuttering. Most of the time if I jump on it, it'll rev up smooth. (Until the 5k cut) but daily driving it stutters pretty bad.

What do you all think this could be? I haven't touched the plugs or wires, even when I bought it. It always ran fine so I never bothered.
 
#2 ·
Sounds like the Opti failing. Mine sputtered and back fired sporadically, like your describing. But eventually it gets worse. You won't be able to start the car, then the next day, you fire it right up, but it won't move without bucking etc. My Opti ended up having a chunk taken out of the top of the cap which sucked moisture right in.
 
#3 ·
How long since the fuel filter has been changed?
That's the first thing I would do.
 
#4 ·
Those are the symptoms mine had when the Opti was on its way out. They don't like the high RPM's. Is the check engine light on?
 
#6 ·
But if it's the opti, wouldn't it do it all the time? When the motor is cold, it runs fine. Only when it gets to operating temperature the symptoms occour.

I don't know if the check engine light is on for that. It was always on because the AIR pump for emissions has been bad since I got the car, so I unplugged the bulb so I wouldn't have to see it all the time. haha.
 
#7 ·
Don't know about the fuel filter. I bought the car at 73k miles. The motor was replaced by the previous owners in the mid 60's because the waterpump failed and messed up the motor. So a motor from a 95 camaro went in which only had 59k on it. I have no clue what has been changed and what hasn't as far as plugs/wires/filter. It's very unlike me to do that but the car always ran so good I never bothered.
 
#8 ·
But if it's the opti, wouldn't it do it all the time? When the motor is cold, it runs fine. Only when it gets to operating temperature the symptoms occour.
That is either the opti or the ignition control module.
 
#9 ·
mine did exactly the same thing before the opti went completely bad 2 weeks ago.....i replaced coil and the ICM but it was still running just like yours then...........dead..........wouldn't start anymore, just replaced mine this past weekend and what a pain, but the car is running really good now.....i would almost put $$$$ on it being the opti
 
#10 ·
Yep, mine only acted up in traffic (hot) when it was going out.
 
#11 ·
Damn... you guys are depressing me. Haha.

I'm going to go ahead and replace the plugs/wires anyway. Since ill need too even if I change the opti. If the problem persists, looks like ill be saving for a new optispark.
 
#12 ·
The opti really isn't that hard to change, it just takes a while
 
#13 ·
I'm not worried about changing it, I'm very mechanically inclined and good at doing my own work. What I am worried about, is cost. I wouldn't want to put a cheap eBay opti in and have it fail, and quality ones are pretty costly..
 
#14 ·
i know it's not the most preferred thing to do.......but i got a brand new one from autozone made by cardone, until i can afford a really good unit like the dynaspark, btw.....i just got a email back from Bob the sales guy at dynaspark and they have rebuilt ones they upgrade for $375 with the same warranty as their new $600 opti's, anyway i know mine isn't that good, but it does still at least have a warranty on it
 
#15 ·
I really don't see the need to shell out the money for a big brand name Optispark unless you drag race every weekend. If your car is just your DD/street cruiser like me, you'd probably be fine with a unit from Autozone or Advance unless you just floor it everywhere you go all the time. I paid $225 for mine from Advance and it has worked perfectly for me.
 
#16 ·
I'm just going to replace the plugs and wires at the moment, since I should probably do them anyway. (Like I said, never changed them) and I have a good feeling they're the original AC Delco plugs.
If that doesn't work, looks like I will be saving up for an opti.
 
#17 ·
Do you think it could possibly be my coil? I was doing some research and quite a few people had the same issues that the coil fixed.

I'm gonna try and ohm out the coil today.
 
#18 ·
I JUST solved this problem. I dumped money into all kinds of things to try and solve it. It was my opti in the end.
 
#20 ·
hmmm, i know they are 2 completley different vehicles, but my 5.0 done that when the fuel pump started going out. it would shutter under load and at high rpms, then the longer you drove it the more it did it. dont know if the fuel pump in a camaro will do the same thing, mine aint gone out yet lol.
 
#21 · (Edited)
Clogged / dirty fuel filter will cause the same thing.
 
#22 ·
It seems like as the hotter/less humid weather got here, it's been running a lot better.

It still has a wandering idle, but I haven't had an hesitation/stutter issues recently and it's running pretty much back to normal up top.

WTF
 
#24 ·
usually when fuel psi is low it either won't run at all or you can barely get it above idle before it shuts down, thats the first thing that went out on mine and those were the symptoms, could also be the icm getting hot and breaking down