For about the last week my car has been stumbling/hesitating/missing at all rpms in open and closed loop. It gets worse under light acceleration, but isn't as bad if I put My foot to the floor, though it still doesnt run like it should. When this started I had a set of Taylor 8.5mm wires ovc, they were pretty burnt up and I thought replacing these might fix my problem. It didn't, the wires I have now are like the stock setup, my plugs are about the same color as all the other plugs I've pulled out of this car in the last five years, however I havent checked for cracks. I replaced the fuel filter because it was old. The gas that came out was almost black. This made a tremendous difference, but the problem still persisted. I searched this site for a while and tested the cts(one on the wp) but its working fine. I hooked up freescan, however I only have a desktop so I can only get info at idle, or while sitting still in neutral or with my foot on the brake. I couldn't get the data to log to excel correctly, so I wrote down what I saw incase it would help. TPS and IAC look good from what I have researched, I haven't had a chance to check fuel pressure yet.

TPS, volts, wot: 4.51
IAC sits at around 33-36 at idle
Map volts 1.25-1.37
Spark advance is between 17-22*
BLM contents was 117-118 (I have no idea what this means I have an idea how it works though)
BLM cell #16
O2 volts L .042-0.97 Integrator : 134-138 (I also have no Idea what this means if someone could explain that would be great)
R .09-.89 Integrator: 121-129
Air Flow at idle: 6-8
at wot: ~294
I'm sure someone is going to say its the opti, as its the original and at 157,000 it probably is the culprit.

Any help is appreciated,
Kenny

 

I would replace the opti. Opti can pretty much do anything to the car, and making it run like crap is one of them. Thats alot of miles for the opti to still be running jes dandy.

BLMs should be 128...Lower numbers mean the computer is using the BLMs to subtract fuel..whatever that means lol. I jes know they should be 128.

 

sounds like my problem.. running rich at lower RPMs with a miss... been chasing it for a year...

I've replaced:

wires (twice)
coil (twice)
plugs (a couple times too)
PCV valve
O2s with Delcos (just today actually)
Fuel pressure regulator
Coolant temp sensor
prev. owner replaced optispark

and checked:
maf numbers seem good & maf is clean
Fuel pressure (its perfect, and doesnt bleed down)
EGR closes fine
no vacuum leaks
Injectors dont drip
checked & re-did my valve lash
pulled belt to rule out load on engine from possible bad pulley

datalogged with datamaster and everything looks great aside from the BLMs that like to sit 10-15 below 128.

I do have a broken manifold bolt & associated exaust leak, but that would raise BLMs not lower 'em. my PCM is reflashed by PCMforless, tried my stock PCM, still does it.


so there's some stuff for ya to try.. maybe one of 'em will work for you.
I'm with ya man... if I get this fixed I'll let ya know what did it.. I'm about to drive this thing off a cliff though. My bud just bought a 2006 S2000... nice, shiney, revs to 9k, but I just cant hang with the whole NO TORQUE thing. I dont wanna have to buy a new car. I like my big nasty boat.

-Ryan

 

I guess I'll check into leaky injectors and then if thats not it, I'll be getting a new MSD opti.

95BlackTA: thanks for the blm info.

Tripkidd: thanks for the list, I'll do the same and let you know what if anything fixes this. Those 9c1's are way more cool than any s2000 ever will be. My dad used to drive one with the local sherrifs dept. when they first came out. It would get up and go, and that was with light bar and cage in the back, plus about 200lbs misc stuff in the trunk. Does yours have the digital speedometer? I remember that being cool when I was a kid.

It is horrible the way these cars run if somethings not working right. Couldnt pass a honda if i wanted to right now.

Good luck to all
Kenny

 

the opti is probally fine since the car still runs and you have no DTCs, i bet your cap and rotor is real nasty though, i would pull it off and open it up and see whats going on inside. a cap and rotor is almost half the price of a complete unit.

 

I second the cap&rotor idea....I replaced mine at around 250,000 miles and it made a WORLD of difference....no more stumble.

 

Im in the same boat i have a new 383 less than 2 weeks old all new sensors,new opti, exept for MAF the car will backfire from the intake constantly and at a stop i would have to gradually tap on the gas so it wont backfire but get on it half way there it goes again now after a week driving the car something gave out completely cuz now it sound like a boat in low gear and smells like i spilled gas inside my car its running reallllllyyy rich and i cant get any answers why

 

In order to do just the cap and rotor, does the entire front fo the engine have to be torn-down, wp, hub, balancer?

playa7970: sounds like and interesting setup, I would like to do a 383 myself one day. It seems alot of Lt1 cars have this stumble and each one has its own cause.

Kenny

 

in your case it sounds like a bad MAF, once when i was playing with the MAF tables in tuner cat and it did almost same thing, backfire in the intake, horrible sputtering and what not. use datamaster to see if your AFGS look normal

 

I ordered a MSD Opti from Thunder Racing yesterday(yeah i know its probably overkill for my car), its on backorder at the moment. I went ahead and got the whole opti since mine has 157000mi on it. This is my daily driver, so I dont want to tear down that much only to do it again if the seal on the old opti were to start leaking. Thanks for everyones input and help.

Kenny

PS Since it is a new product I'll keep updating after the new MSD opti is on the car.

 

thanks for the info !

 

So its been a month and still no Msd Opti, they are still on backorder. So I got a great deal on a Delteq bare bones setup(read less than msd opti ). I didnt want to tear down the wp and hub/balancer asembly again anyways. I cant wait until it gets here. Woo Hoo no more Opti!!!