snunicycler

my oil guage keeps going up and down, usually when i stop or go the needle plunges, sometimes so much that my "check guages" light comes on. but only for a second or so. then it goes back up and stays put until i stop again.

also, this may be related or it might not, my CEL is on, cylinder 3 misfire. i have replaced the spark plugs, the spark plug wires, the distributor cap, and the rotor. i took it to a mechanic who said my head gasket may be leaking but he couldnt tell for sure without taking it apart and looking at it. i hesitate to do that.

does anyone have any idea about what either of the problems is?
thanks guys!

snunicycler

after a little research i found someone who had a problem with whatever their car was, and the problem for the oil part was a bad oil pressure sending unit. so i am guessing that if that is the problem, it is unrelated to the cylinder misfire.

but i still was hoping for some opinions about my misfiring cylilnder. the only thing i could find on this forum is a post by tahoeMD, he helped someone with a cylinder misfire and the problem ended up being a bad crank sensor. my SES light is on most of the time and only blinks while i am idling. other than that it runs fine as far as i can tell.

does that sound like it could be the problem? or am i barking up the wrong tree? anyone?

princessauto

to double check you can hook a manuel guage up down by the oil filter, their is a nut down by the oil filter on the block if it is still going up and down it sounds like crank bearings.
princessauto

snunicycler

oh ok, cool. i dont really know what a manual guage is. are you talking about a tool or an actual gauge? i have a fuel pressure guage, can i use that?

chase050505

My 94 was doing the same thing and a week later it started knocking then it eventually crapped out. The mains were shot, piston rings were gone antifreeze was in the oil. Im not saying for sure that any of that is wrong with yours but its a possibility. If I were you I would start running different test on it to be sure.

snunicycler

good advice, but uh... what kinds of tests do you think i should be running? my oil level is fine, i checked it once i noticed the gauge. it's due for an oil change in about 3 weeks/200 miles, i might go ahead and do it now. other than that i dont know what tests to do. my spark 3 cylinder plug has been getting ash deposits on it so.... coolant in the oil? that is what the mechanic said.

what tests do you suggest?

chase050505

I would do a compression check, ive never done one myself so im not sure exactly how. When you change the oil check to see if its got antifreeze or water in it. If it does it will be a light colored oil. If so it could be cracked heads or blown head gasket. Let the motor warm up and listen for it to be knocking, it will sound like someone is under the truck knocking on the bottom of it. This would indicate worn crankshaft or main bearings. I would also check the coolant to see if there is any oil in it. The last thing is, is it smoking out of the tail pipe? This would indicate worn piston rings and it if is what color is the smoke?

snunicycler

the mechanic i took it to did a compression test and said the compression was fine. so that is good. when i get my oil changed i will ask them to check for antifreeze/water. good idea. i think though that when i checked the level from the dipstick it was the normal dark brown color that used oil usually is when it is close to needing to be replaced. the mechanic wants to open it up to check my head gaskets.

i have not noticed any knocking or any unusual sounds. my coolant is still the bright red it should be i'll check for the smoke next time i'm driving and i'll report what i find.

thanks for getting back to me!

DoubleO7

Redneck headgasket leak into rad tester:
Place household carbon monoxide alarm in plastic bag.
Rubber band top of bag over open radiator opening.
Run engine up to operating temp.
If bad head gasket is allowing exhaust fumes into water jacket, they will set off the alarm.

Just because the oil is not milky, does not mean it is not leaking into the oil. Although if oil is clear, it would be a very small leak. Look under the oil filler cap for droplets. Taste them: if sweet, it is antifreeze, if not sweet it is condensation from not being warmed up enough long enough.
The underside of the oil filler cap should be dry.

You will see plumes of white moisture evaoporating until everything is nicely warmed.
Running only 200 miles per three weeks might not be enough per trip to get everything up to temperature to evaporate off condensation.
You might also have a O.E.M. intake gasket leak at the very back of the block, the 5.7L from the 90's are notoriously famous for that.

DoubleO7

I would not let your mechanic take it apart to "check head gaskets".
If you tear it down to check the head gaskets, you put new gaskets on no matter if they are good or bad.
And if your paying the mechanic the industry standard to dismantle the engine to "check head gaskets" your pushing $750 or more in labor cost alone.

And your oil pressure gauge sending unit could be going bad.
It is cheap and located behind the intake and on the driver side on top of the block.