oneslowz28

ok guys heres the problem.

i have a 94 z28 and ill will be crusing at 50-55 mph and the tach is at around 1700 rpm and ill give it a little gas to bump it up to 60 mph and the car stars shaking and stuttering. is my opti going bad? also my lights interrior and exterior will start flashing and my volt gauge will jump from around 14-15v to 18v and down to around 10v i think my alt is going bad but checked the voltage from the alt and it stays constant at 13.5 volts someone said my batt. is bad but if that was the case wouldnt it die fast if i have my radio on without the car running?

any help is appreciated. thanks

oneslowz28

can i get some help?

got8?

change your plugs and wires see if that fixes it

oneslowz28

plugs and wires were replaced 3 weeks ago

NEED2SPEED

Did you change the distributor caps when you changed plug wires. Does it run fine when cold then after it warms up it starts shuttering and rough running? Check the cat. converter. As far as the volt gages. check all the grounds from ignition to starter.

got8?

how is your high rpm power?

MentalCaseOne

I am very curios about checking the grounds from ingnition to starter. He say his voltage appears to be jumping to 18 volts..... sounds like a loose ground when the engine twistes under load. how does the starter gets involved into this? I have seem my bolt gage fluctuate when the engine is warm. I havent seen and sparks at the new opty or wires/plugs. I a small way I suffered the same problem he describes except it only does it while my car is at idle...

Can you explain how does the starter wiring comes into place while he is in motion?? or is there a ground conection at the starter that may come loose??

Marvin

MentalCaseOne

If the voltage at the alt remains constant it doesnt matter if your battery was dead... the engine will run on alt alone without the batt... if the bat has a short then it would either kill the alt.. of burn something inside the batt... the wild voltage swing is what I am interested on... is it at the gages only or is actually happening from the voltage supply... you said its constant but have you found a way to measure it at the batt while driving it?? is the voltage swing happening at the batt while you drive or is it just at the dash gages??

I have a brand new alternator and I have observed voltage swings of from 12.9 to 14.1 .... 1.2 volts total measured at the alt... I wonder if its the ingnition flashing over at the plugs or something similar whats causing the voltage load to drop some voltage... sometimes I think its that conection that goes with the small wires in the back of alternator..... bad conection or loose ground somewhere..

I will do some checking tomorrow and if I find anyting interesting I will post here.

marvin

oneslowz28

Well guys the problem stoped for a while and i figured all was good. But thats what i get for thinking. Took the car to the track lastnight (read my post bad night at the track) and to say the least the prob. is back. this time much worse . the car stutters under a load again but there are times i cant get over 50 mph. I thought it might be the fuel filter so i replaced it and it needed it the fuel that came out of the tank side of it looked like used oil. so i droopped the tank and cleaned it out and i thgought this would fix the prob. well after finishing up around 8 tonight its still "bogging" or "stuttering" under load. Im hoping its the cats when i check them tomorrow. the voltage is still fluxuating <sp>. we tested the alt and bat. and there both good i checked the voltage at the alt and bat. and there fine but if i check from a accessory like the cig lighter or a tail light its still juming from 16.3v to 10.1 volts. i checked it at a relay under the hood and its fluxauating just like on the inside. i checked all the grounds on the enging and body that were under the hood. is there susposed to be a ground going to the tranny? if there is i couldnt find it..

any ideas on what to check next if the getting rid of the cats doesnt work?
and anyidea what could be causing the voltage spike/drop?

JDman

Dude,
I'm having the same problem, it's the opti. I'm trying to find a deal on one online. Forget about the cats your wasting your time. Change the opti.

TobyZ28

I have had the identical problem your talking about for 2-3 years now. I've done EVERYTHING mentioned to try and fix it.

Opti, Injectors, Plugs, Wires, EGR, Coil, Fuel pump, fuel filter, New Engine rebuild, O2 Sensors, new CAT etc etc.

Still not fixed. The problem was ONLY at the speeds you mentioned and it seems to be more prominant going up hill too. A lot of posts saying check for arcing etc etc. The interior stuff though i don't have... Car runs 100% fine everywhere else right?

Anyhow i'm getting a new alternator put in maybe today and who knows, maybe that will fix it?

There isn't muich more i can replace in this car...

TobyZ28

I didnt see that post! Sounds like your CAT is plugged. I had that happen to me as well IDENTICAL results. be careful, your exhaust manifolds are probably glowing red after a bit of driving, very bad for the head gasket Replace it asap and keep driving to a minumum!

Bad64chevelle

Mine did the same thing....my lights would flicker, the stutter would get me if i gave it gas around 2200, and it lost ALL power. it was the Opti.

oneslowz28

but the opti is less than a month old so i doubt it could be it i dont wanna fork over that kind of $$$ again for a car i only gave 1500 bucks for

Bad64chevelle

Well it may be something else, like a ground strap, however mine did the same thing when the opti went. If it got wet, or maybe it was defective, or not installed correctly. Start checking ground straps and what not....but i have a feeling it is the opti