Here'* the story..
I inherited a 94 Olds Royale from my sister-in-law. It'* got 158,000 miles on it. She just drove it back to MI from WY last week.
The car runs like ABSOLUTE crap. It shakes and shimies very badly. It won't idle smoothly and constantly feels like it'* going to stall. It'* even worse when in gear with your foot on the brake. When trying to accelerate it has NO power. It does have the 2.73 gear ratio, but still it'* noticable there'* a problem. When accelerating hard (and when the windows are down) you can hear what sounds to be chains dragging on the cement (for a lack of a better term). Something sounds like it'* jingling.
I've changed the plugs, wires, air filter and fuel filter. I did an oil change too. None of that helped. So, I took it to my trusty shop and they poked around with it for 3 hours and hooked it up to their GM Tech II system and found no stored codes. They did find that cylinder 4 was throwing errors, but the Tech II wasn't giving a trouble code or diagnosis. Each cylinder has 95 lbs. of constant pressure and holds it. The mechanic swapped injectors with a good injector from another cylinder and the problem still exists. He thought that the cam position sensor could be bad or the crank position sensor. He also suggested that the lobe for cylinder 4 on the cam shaft could be badly worn...causing the rough running.
So, with no codes, fresh tune up and out $70...I'm at a loss for what to do next! The mechanic and I both believe the cat is not clogged. It doesn't rattle when shaken. I also changed the cam sensor (per the mechanic'* advise). That didn't change anything. BTW, I'm still getting 24 MPG and she will cruise down the e-way all day and night without an issue.
The next few things I thought about trying are.... New PCM, crank position sensor, new cat, and/or a new engine (used from the bone yard).
I really hate to keep pumping money in it foolishly. This is making me nuts. I've never seen a 3800 (an L27 at that!) run this bad.