atlantadan

Hi All -

Ive got a 96 caprice with the LT1. Since I've owned it, it has felt like it's missing, and it's averaging 15 mpg. The car has true dual exhaust (no x-pipe) so the exhaust pulses can clearly be heard.

The previous owner installed a new opti not long ago at all. In the past 2 weeks, I've installed a new ICM, new plugs, new EGR valve, replaced all the rubber lines and seals underhood, different injectors, cleaned the MAF, checked the intake boot for leaks and whatnot, plug leads, and I ran a compression test. Everything was 160-170, so we're good there. Vac test showed a dead-steady needle. Fuel pressure was ok.

The car fires RIGHT up - like within 1/2 rev of the starter. No CEL's other than from when I was monkeying around with plug-leads and injectors. Pulling the leads and injectors for each cylinder affected the idle. The plugs were all acceptable in color and content. Doesn't blow a hint of smoke and doesn't smell rich. Just passed emissions.

From my days of working with a distributor, it almost feels like it's waaaay out of time due to the choppy acceleration and poor fuel mileage. When I romp on it, you can feel the shudder in the car as it goes down the road. Hot or cold - doesn't matter and never changes. Questions are as follows:

- Possible opti again? Any way to test the cap without removal?
- I've read that it isn't possible to install the opti incorrectly, then I've read you can. Would the car run if it was installed incorrectly or would it manifest as a 'no start' issue?
- Would a bad exhaust valve show in this way?
- Could it actually be the lack of an x-pipe in the exhaust and the individual Flowmasters beating me to death?

The car "chuffs" as it rolls down the road, but the dollar-test was inconclusive. This is why I initially thought of a burned valve.

Thanks for your input. I'm tempted to just pull off the opti and see what the hell is going on back there...

mguidry629

iTrader: (6)

You didn't mention plug wires, have you inspected them/changed them?

Do you know what kind of opti it was replaced with? Have you checked the opti harness? I had problems with the opti harness and thought it was the opti.

I would think a 96 caprice would have an O2 behind the cat. Do you have any cats on the true duals? And is there an O2 behind one of them? If you don't have a CEL light, then you're probably OK there, just thought it was worth a mention.

If the opti was off, it would be by 120 degrees, so it wouldn't even run.

atlantadan

Replaced wires and yes, it has cats. The Pre-cat 02 sensors are new, I did not replace the post-cat 02's. Is there an ohm test on the harness or something or should it just be replaced?

Thank you