Used '94, comes with one Gremlin

[NuggetSlapper]

I just picked up a '94 ragtop two weeks ago with low miles (77k) and according to the DMV records, the last ten years shes been garaged/car-parked as a Sunday cruiser with only about 1000 miles a year average. It's been running great with all original parts except tires and vinyl top. But here is this one Gremlin.

Last week the check engine light comes on. The oil pressure I note is low (I'm in 5th doing 70mph). I swing into a station and pop the hood. Plenty of oil. I have the guy run an OBD check for $20 and nothing is there. No errors at all. I pull out and within a block the gauge pops back up (from 10 o'clock to it's normal 12 o'clock position) and it has been fine since.

Yesterday morning while driving six blocks from the house (still a relatively cold engine) the "Coolant Low" warning light comes on. I swing over to my mechanic. Plenty of coolant, nothing on the scan. I restart the car and there is no error. It idles to mid-warm and you can hear the fan switch on and see the gauge lower as it cools. The coolant levels stay in specification in the filler can from cold to warm. The problem just went away.

As I understand it, these OBD1 cars wont save a trouble-code or store pending codes?

Any trouble-shooting suggestions? I feel a little negligent running a vehicle with warning lights just so I can read a code some time later.

 

[Blakonblak94]

My check engine would come on at times when the car would be warming up, happened to be o2's. How is he tested the obd check because you could do it yourself for free my friend.

 

[teal94gt]

low coolant light is caused by the sensor in the overflow tank my only does it when i has been driven for a couple weeks when temps are below 60 degrees

 

[BruhBrahBrad]

This kinda happens with my 96... it gives me a low oil light...I check it and its good... the gauge stays constant at the A in Normal.

 

[JDwhite98gt]

My oil pressure gauge flutters based on my throttle position lol but its because there's a little wire that just pushes onto a threaded rod on the oil pressure sending unit. It gets loose ver very often and every now and then Ill find it hanging off with my gauge reading no pressure. Dont know if 94's have that or not. Also check in your coolant overflow bottle and make sure that the floater moves freely and nothing is making it stick.

 

[Mustanger]

the oil pressure sending unit goes bad frequently and causes the pressure to flucuate wildly at times. Only a $13 item & a few minutes to change. Mine is steady as a rock...but will add a true gauge soon.

 

[Addermk2]

Is your mechanic smart enough to know to scan the CEL from under the hood?

Also, before starting and driving the car, check the level of the coolant in the overflow bottle, not the radiator. As the car warms up, the coolant expands, going out into the overflow, and the next time you start the car (engine warm) there will be coolant in the bottle and the light will not come back on.

as fopr the oil pressure, like Mustanger said, replace the sending unit that is next to the oil filter. They get clogged up with coked oil and go bad.

 

[BruhBrahBrad]

Are the oil pressure sending units for 4.6 the same way?

 

[NuggetSlapper]

...How is he tested the obd check because you could do it yourself for free my friend.

@Blakonblak94 Free if I buy an OBD I scanner I suppose. Might do that if it keeps happening.

Is your mechanic smart enough to know to scan the CEL from under the hood?...

@Addermk2 He thinks he is LOL! I checked it absolute cold as you suggested and before starting and it was one CUP low. Hasn't happened since adding just a small toss of water. Coincidence?

... Ill find it hanging off with my gauge reading no pressure. ... check in your coolant overflow bottle...

... sensor in the overflow tank ...

@JDwhite98gt @teal94gt All going on my maintenance check-list

the oil pressure sending unit ... Only a $13 item ...

@Mustanger $13? That's worth the piece of mind.



Thanks all!

 

[Blakonblak94]

No, you can run a jumper wire on your obd test box to read cel blinks. So entirely free. No "reader" needed.

 

[bsn95w]

Sending units are bad...

The oil pressure sending unit messed up about 2 days after I bought my gt.. Was a hard freeze and I started my car to warm it up, went inside to finish getting ready for work, then got back in the car and nearly shit myself when I looked at the dash and had no oil pressure... So I imediatly shut it off. I didn't hear a knock or even a tick when I walked up to the car, so I started it back up, and had great oil pressure... A few seconds later it dropped back to zero, so I gave it a little gas and it jump right back up, was fine and and then dropped down again... And then I just held it at about 2k for a few seconds untill my temp guage staged still... Then my pressure guage never droped down.. 2 days later I replaced the sending unit and haven't had a problem yet... Also my sending unit was only 7 bucks.

And my low fluids light came on about a month ago, checked it, and it was full, but the water was deffinately mercky... Flushed the whole coolant system, and the light wouldn't go away... Pulled the sending unit out, and it was covered in nasty crap, and a prong was bent on it... Cleaned it off with some carb cleaner and reinstalled it, and it went away. The light comes on every now and again if I don't drive the car for over a week, but goes away if I cut he car off and start it back up... So I'm realy assuming that that's just the sending unit too.

Sounds like the same is wrong with your car... Probly less then 30 bucks tofix and you can do it yourself with a cressent wrench.

 

[CC'S95GT]

No, you can run a jumper wire on your obd test box to read cel blinks. So entirely free. No "reader" needed.

A Haynes/Chilton manual will tell you how to do this. And tell you what the codes are. Best and first $15 bucks I spend on any car.