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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. I only changed the one that was bad.

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.

Update: The problem turned out to be that I was in need of new plugs and wires. One weird thing is that my check engine light turned off on its own. I thought that on vehicles that are 95 and older, that the battery or fuse had to be disconnected to reset the check engine light.

Reply to
Reasoned Insanity
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Chances are your '95 already has OBDII in the ECU. I had a '95 Tercel and it was OBDII compliant, but they still had to do the old style emissions test, because 'oficially' OBDII didn't start until '97.

Good thing, since the ECU kept throwing a P401 code, and did it every third time I ran the car. When inspection day would come around, I would unplug the ECU power cable, reset the ECU and send it in for the test. Passed every time!

Reply to
Hachiroku

Oil too high? I would either check the oil to make sure there isn't fuel in the oil. If a plug wasn't firing right, the fuel could leak past the piston rings and into the crank case. Oil diluted with oil doesn't lubricate well.

Jeff

Reply to
Jeff

Trouble code 25 is an OBD I trouble code.

Reply to
Ray O

Some trouble codes are self-clearing. As for the engine running smoothly now, that means that the spark plug fouling was a symptom, not a cause. You may have a leaking valve stem seal. Watch for lots of smoke from the exhaust when starting the engine after it has sat overnight.

Reply to
Ray O

I could do it either way on my Tercel: I could short the Diagnostic connector under the hood and read the flashes, or we could plug into the diagnostic connector under the dash with a code reader and read the OBDII code!

Reply to
Hachiroku

Hmmm, I didn't know that any cars were set up that way.

Reply to
Ray O

I thought it was odd, too! I saw the "Diagnostics" connector under the hood, but when I took it to a guy who had a shop, he gets out the code reader and plugs it in under the dash! It spit out the P401 code.

Maybe because OBDII wasn't 'official', htey still included the connector under the hood just for us Ol' Timers.

Reply to
Hachiroku

True, a fouled plug, unless the center-to-case resistance is > 10 ohms should be changed out.

Keep an eye on that plug. If the source of the problem (eg oil leak) isn't cleared the plug could foul again.

Reply to
johngdole

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