I have a 1990 cadillac deville northstar. Recently it started to run rough, and was shaking pretty bad. Decided to do some routine maintenance, since it was my father's car before me. I checked the plugs, and found black soot on cylinder #8, so I changed all the plugs. I ended up getting the same result, a sooted up plug on #8. I tried a wire from a dif cylinder, and got the same results. I then decided to pray, so I changed the air filter, no luck, then the fuel filter, no luck. I then went the more expensive route, and changed the fuel injector on the cylinder, and again got the same results. I then changed the coil, and got no results.

I'm getting to the point where I am stumped. I have talked to my dad, and he gave me a few more facts. The battery has had to be changed 3 times in the last two years, because the cells fail. The battery would die if you leave the car for 4-5 days and not drive it, and it would need to be charged/jumped before it would start.

So...could it be that this battery drain is messing with the ohms and making the fuel injector misfire? Or where else should I start to look? I have spent alot of time working on this, and am trying to get some new ideas. I can change alot of things on cars, but I have never messed with the fuel/electrical system on a car until now. Any help at all would be greatly appreciated.


Thanks,
Detra319


..........
mod edit title

 

can you pull codes? how many miles? have you changed the plug wires? let the forum know at what point did the car start running bad? what were the conditions, weather, driving conditions, highway, intown, etc.
is it a dead miss all the time, or at certain rpms does it go away?
welcome to the forum, and get back with a little more info.
rickyd

 

I have not changed the wires, but I tried a wire from a different cylinder and still got a misfire on the same cylinder. I could prob drive it to autozone and have them pull the codes.

The car was being driven by my brother exclusively highway miles. He would drive 11 miles to work and back, and that is it. He claims to never have driven it otherwise, as his girlfriend has a car. I think the first time it happened was driving to my house, on the highway, in clear conditions. No water getting splashed into the car that I know of.

 

Just want to be clear on the engine in the car. You say it is a 1990 Deville with a Northstar. Something is not right. Northstars were not made until 1993. If the car is a 1990 then what engine are we discussing? If it is not a 1990 then what year is it?

About the only things you have overlooked are vac*** leaks and emmission system parts.

 

Hmm i r not so smrt. Heh...anyways. Its a 1990 deville 4.5v8, but not a northstar.

So what am I checking for vacuum leaks, and what should I be doing to check the emissions systems?

 

I've reread this all, I think you need to get new wires, that's the only thing you did not address. If these are original then they are long overdue to be changed. On the plugs, are the properly gapped ? A misfire is usually in the ignition parts, plugs, wires, coil.

Vac*** leaks, you just need to look at all hoses and make sure they are not cracked or split, make sure no open ports.

 

Alright, I have new wires that I will install in the morning and get back to you. I also gapped the plugs myself, as I never trust that anymore. Thanks alot for the help!

 

So I changed the wires today, and restarted the car. It is really idling rough now. I put it into gear to adjust how it sat (was on a small hill), and it started to race after I put it into gear. I moved it 10 ft or so, and put it into park. It then revved very high, prob 4-5k rpms, but then dropped back to its rough idle. It would rev a bit, then slowly idle down, rev a bit more, and repeat. I did notice a hiss that I can't remember hearing as well. I went back through and checked everything I have installed so far, and nothing appears to be out of place or installed incorrectly.

Now I am getting stumped. Should I risk the drive to autozone to have them pull the codes?

 

Check the link. Can you get the codes yourself?

http://myweb.accessus.net/~090/dtcobd1.html#ide

 

All I got was e52, but I also had the battery disconnected to prevent power drain. Should I restart the car and run it for a bit before I attempt to pull the codes?