1. Home
  2. General Toyota Forum
  3. 95 Geo Prizm

95 Geo Prizm

About two months ago it began running rough and burning a lot more gas than it should. I eventually figured out that it was simply a bad spark plug wire.

Today it started exhibiting the same signs again. I checked the wires and they all look ok. I went ahead and pulled the plugs and all of them look nice with a powder gray look to them except one. The one that doesn't is dark and has oil on it. I checked my oil and I do have slightly too much. Any thoughts as to what I can do to get my car running right again? Thanks in advance.

PS: Both times the check engine light was pulling code 25.

Reply to
Reasoned Insanity
Loading thread data ...

Diagnostic trouble code 25 is air fuel ratio too lean. DTC 26 is air fuel ratio too rich.

The spark plug could have oil on it because one or more of the valve stems for that cylinder is leaking and fouling it, or it could have oil because it isn't firing and burning off the normal oil and fuel in the combustion chamber.

What brand spark plugs, ignition wires, cap, and rotor are you using?

Check the condition and resistance of the ignition wires and check the condition of the distributor cap if it has one.

Regarding the slightly high oil level, it could be that the last person to change the oil overfilled it, you could have a leaking head gasket, cracked head, cracked block, leaking fuel injector, or you drive a lot of very short trips.

Reply to
Ray O

Are you using oil? Is the engine smoking blue smoke? The fouled plug should be changed out.

There are many reasons for plug fouling. Given that 3 other cylinders are OK and you have a oiled wet plug, then the oil control rings in that cylinder probably aren't up to their jobs. A leaking head gasket or a worn valve guide leaking oil into the cylinder can also do it. If you have a plugged PCV system then all plugs will be the same. So this points to a single cylinder problem.

Excessive oil can affect the ability of oil control rings to wipe the splashed oil from the cylinder walls. So drain some out or do an oil change and make sure the proper amount is added. If that cylinder's oil control rings are bad this should help for a while (eventually the rings will wear out). Where did you get this oil change?

  1. Check the resistance of the ignition coil and distributor. A Haynes manual from Pep Boys can help. Or find the engine in the following link. Now, the new wire should be OK, but check the wire resistance (<
25 Kohms, usually 10-12 Kohms).
formatting link
  1. Drain excess oil or do a proper oil change. OIl should be between F/ E marks. This may help any marginal oil control rings.

  1. Replace the fouled plug (or all 4 with NGK G-Power) if center electrode to metal shell measured < 10 ohms (> 10 ohms the engine can be started normally)

formatting link

Reply to
johngdole

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.