Replaced plugs, wires and coil packs - 4 plugs still look burnt?

I just had my engine replaced and started to notice a misfire and surging while idling. I replaced my wires and plugs but still noticed the same problem. I then replaced all the coil packs and the car ran perfectly for about a week!

Now, after a week of driving, the car has begun to have a slight hesitation after pressing the gas. I pulled the plugs and noticed that the front 4 plugs (cylinders 2,4,6,8) looked burnt as if the car is running rich, but the back 4 plugs (cylinders 1,3,5,7) still look brand new. What gives?

How can the front 4 plugs look so burnt and the back 4 plugs look as if they are brand new?

Is this a FPR problem or an oxygen sensor gone bad or maybe Fuel Injectors? I do notice a tink, tink noise around the exhaust system after I shut the car off... could the exhaust systmem (cat) be a problem???

Thanks in advance!

I know someone on here can help me?

I spoke with a mechanic (friend) today, who said it is most likely the O2 sensor for that bank, which sounds correct, since the 95 has two O2 sensors (one in front just under the exhaust manifold and one in back somewhere??).

I will try my luck with replacing the Front O2 sensor, since this is where my plugs are getting that burnt look and then repost my results.

Wouldn't a bad O2 sensor turn on a check engine light?

Jeremy

Jeremy, Thanks for the reply!

I am not sure about the Check Engine Light; It has not come on at all? however, I will go to Advance Auto and get it the computer scanned today and post my results later!

Another Question: Is it possible for the O2 sensor to go bad without the Check Engine Light coming on? If not, then what would your assumptions be?

my guess if fuel presure regulator - the FPR usually won't set a code and the O2 sensor will.

The FPR will also dump lotsa fuel directly into the intake via the vac line; making run rich.

He's probably right...I don't have an Aurora, so I don't know too much about them...I have an Alero.

Jeremy

Thanks, I will check the FPR, but now onto my latest fiasco...

Ok, Here's the latest scoop on my vehicle. With Codes:

I went to Advanced Auto to have my car scanned but they could not get it to read properly, so I bought the O2 sensor anyway. As soon as I drove away, My Service Engine Light came on and the car drove horribly and would not shift into higher gears.

I replaced the o2 sensor when i got home and drove the car; again, the same shifting problem?

This morning, I took the car to a mechanic with a better scanner. Luckily, they didn't charge me for the scan, but I found out that my solenoids in my trasmission may be bad. Here are the codes they pulled when they did the scan:

Codes:
29 - Shift Ratio
39 - Torque Converter Clutch Malfuntion
36 - EGR Pintle

I had the solenoids replaced last summer, could this be what the problem is again?

BTW, the car does seem to idle alot better now sence the O2 sensor was replaced...

Check your Mass Air Flow sensor. Tranny shift problems along with engine hesitation can be symptomatic of MAF sensor issues.

FPR is a good simple thing to change out, but it wouldn't typically give you tranny issues. Could be a fuel issue and a tranny issue...two separate things.

Another issue with idle on some of these cars(including mine) is the backfire gate on the intake doesn't seal and the fuel/air mix is off and plugs can run hot.

anyways.... just some ideas. Good luck.