flexus

After many many service hours car has new plugs and wires, clean injectors, new fuel filter, runs pretty decent if i drive it calmly. When i want to floor it it starts loosing power, especially noticeable while in 2nd and 3rd gears, when it feels like it has power gaps while going up in the RPMs. After this, the car feels like it's running in 7 cylinders. In idle the engine shakes, bangs, feels bad, when i accelerate it bangs all the way up and feels powerless. This can only be cured by shutting down the engine for 5 minutes or so and starting again. It then goes back to normal and runs in all 8...

I can only immagine this is from the opti... So, what i would like you to suggest is how it is best to fix it. Should i buy a cap and rotor kit or change the whole unit. Should i go with ACDelco (or stock), Accel, MSD, they all have both kits and whole unit. Cost is an issue, as i've spent A LOT on repairs recently and i'm going into debt...

Thanks!

Bawls

I just had this exact problem. I went with a stock replacement optispark. Only $305 for the unvented from Jason Cromer. The vented version is even cheaper.

93yellowta

well I thougt I would throw this out there, have you replaced the coil yet? coud be a cheap fix before the opti replacement...

flexus

Do you think my problem could be caused by the coil only? I need to eradicate the problem not make it "a little better"...

My main concern is the choice between cap and rotor kit OR whole opti. I may buy a MSD or Accel coil anyway as it's only 50ish$...

udlose94z28

How many miles is on the car?

flexus

50k something almost 51k. Car has been very poorly serviced up to now by previous owners, i assume nothing has been ever changed...

Injuneer

You seem to be indicating that it runs fine after a cold start, and only seems to act up after its been warmed up, you push it hard and starts losing power. You also indicate if you turn it off and start it up, it runs fine for about 5 minutes, then starts the problem all over again.

I'm thinking its related to the PCM going into closed loop, which typically takes about 3.5 minutes after startup. Have the O2 sensors ever been changed?

Another possibility would be things that might break down when they get hot - coil, IC Module, opti optical sensor, wire insulation, injectors

flexus

You got things a little mixed up. First off, it doesn't always start up fine from cold...sometimes it does sometimes not! Then, if i drive the car around it works fine even for an hour, but the instant i push it up to 5k+ rpms it starts running in 7 cyls. After that even if i cruise nicely it won't stop banging unless i shut it off for 5 minutes. If i shut it off for 5 seconds, pull the keys and start it up again it won't work fine again! While it's running bad if i rev it up sitting still it produces backfires in the exhaust too!

Guest47904

Why are you dead set on it being the opti?

Have you tried forcing it to open loop by unplugging one of the front O2s?

Have you tested the response of the MAF by measuring the yellow wire for 3.7 volts or more when you snap the throttle while it's running?

Did you scan it for codes?

Did you look at what the fuel trims or the O2s are doing?

What portion of the opti do you suspect is the problem? Low voltage or high? Set up a test for it.

93formula

as for your cap and rotor or whole opti choice i would replace the whole opti, your gonna tear it apart to go that far you may as well replace the whole thing. as for the opti being the culprit, im not sure till you do the above tests.

flexus

To be honest i wanted it to be the opti so i could have a fast and easy solution, and not too expensive... I don't have any *competent* people to service this kind of cars aroud here... i don't have the knowledge or equipment to do what you said myself. Every service i've been to keeps charging heaps of money for things that so far improoved my ride but no-one seems to be able to make it run right. I'm trying to take matters in my own hands and find the problems myself...have them only replace the parts i think are faulty.

I will try what you said there, i'll try to make the ppl at the service try them, maybe i can find something.

flexus

I've been to a service, they put the tester on the car and it showed normal O2 readings, the MAF seems to work too... I think i'll go ahead and buy a cap and rotor kit and new coil, with the fact in mind that they have never been replaced anyway, and may be worn even if they are not the reason for my recent problems.

Please recommend a manufacturer for cap+rotor kit and coil too. and maybe an online store as well. thanks

93formula

if your going thru the trouble to get to the opti you may as well replace teh whole thing, get a gm opti from dal or jason, and get a stock gm coil.

flexus

I would but i'm low on cash and a 300$ opti will cost me 500$ to buy from where i live. But a 120$ cap+rotor will cost about 250$ only. And as far as i know they are the only moving / sliding pieces inside the unit so the rest of it shouldn't wear...right?

Sorry for not mentioning, but i live in europe, and need a store that ships worldwide... I found Dal's but i don't think they'd ship to me...i'll call there anyway...

Bawls

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