Engine surge/cut-out and Code 45

[kustomkyle]

I have a 1986 Buick Regal Limited with the original 307 Olds V8 and 200-4R with approximately 97,000 miles on it. I've never really had much of an issue with fuel/spark, but recently the car has become hard to drive. Basically, it runs decent at lower speeds (in lower gears) but once you get to about 50-55MPH it starts to miss and then starts cutting out/surging. In other words, accelerating and reaching 50MPH, you can start to feel the engine start to miss and it starts to get worse if you stay in the gas; then at 55MPH it just cuts out. To get to work and wherever else, I can aleviate the symptoms by being very easy on the throttle and very slowly work my way up to 50-55MPH without too much trouble, but it doesn't work all the time.

So far many things have been checked/replaced and nothing has helped. Here is a list of what has been replaced relating to fuel/spark/emissions:
-fuel pump (replaced 2 years ago, the old one was still good and was misdiagnosed as the problem, which was the catalytic converter)
- fuel filter
- gas tank (replaced when rear frame rails were replaced May 2009)
- sending unit
- rubber fuel lines on sending unit
- Oxygen sensor (once 2-years ago and again today)
- Distributor cap
- Rotor
- spark plugs

Checked the trouble codes and it flashes Code 45. My repair manual said this meant there was fuel in the oil, the oxygen sensor was reading rich, air filter clogged or fuel in evaporation tank.

For whatever reason I really thought the oxygen sensor would fix the problem, but it didn't do much of anything. I've been told it may be the thermostat, but the car really doesn't have much of an overheating problem at all. The car seems to be running very lean, since the spark plugs were white and the engine spark knocks a bit, but the Code 45 seems to

 

[megaladon6]

the O2 is reading rich due to a misfire--you have unburnt fuel being dumped down the exhaust. the ECU is leaning out the A/F ratio, thus the white plugs. check your ignition system. first check the timing, according to the manual. then check the ignition module, this is the most likely problem, but it could also be spark energy.

 

[kustomkyle]

Ok thanks. I forgot to mention the timing is right where it is supposed to be. I've also heard of the ignition module like you said, as my dad's 1992 Roadmaster had to have it's replaced (but I think it had totally different symptoms).

 

[megaladon6]

modules don't also die in the same manner. the good thing is that they're cheap.
btw, if you need a coil, i recommend the module also, as a weak coil can be hard on it.

 

[Blake442]

I see plugs, cap and rotor on that list, but no wires...

Replace your plug wires and also make sure they're in the correct locations.

 

[kustomkyle]

Would a "mixture idle control solenoid" go bad, and what kinds of symptoms would it cause (looks like it is just an electrical connector)? Or a "idle stop solenoid"?