Tachometer problems
 

My 95 saturn sl2 runs fine but the needle on my rpm gauge darts back and fourth and every once in a while it will cause my car to stall and I just need help on figuring out what's wrong and how I can fix it. Can I get some help please and thank you.

How many miles on the cat?
Manual or automatic?
Does the needle just bounce or do the rpms of the engine increase and decrease with the needle?
Is the needle constantly bouncing around or Is it once every 2 days?
How much is it bouncing around? A few hundred RPM or 750 to 1000 rpm or more?
What rpm does the car idle at when warmed up and is it a steady idle?
Does the issue happen more when you are accelerating or slowing down?
Does your car lose power when trying to climb a hill?

How much oil does the car burn every 3000 miles?
Is the service engine soon light on?

It's much easier to diagnose these kinds of things by having you provide the basic info up front. Then we can systematically go through and troubleshoot the car. I have a 95 SC2 myself (same engine) so as long as you can provide answers and perform low tech checks and cleanings we should be able to find the cause.

It's the stock cat at 150000 miles, its automatic, the needle just bounces but every once in a while it will drop the rpm of the car, it fluctuates from 1000 rpm and 850 at idle, it happens more when I'm stopped than slowing down but it doesn't do it all the time, I dont loose power up hills, idk how much oil it burns every 3000 miles, my service engine light comes on cuz my trans like to shift hard into second gear but not when my guage bounces. Thx man.

Are you sure there aren't other codes stored except those for your transmission? With OBD1 cars at least with Saturn you need to read the codes through a flashing sequence of dash lights. you use a paperclip to cross to specific pins on the aldl. Search paperclip method on the forum and you will find out how to do it and what to expect. I will help you decipher the codes.

850 to 1000 is too high for an idle at operating temperature for a dohc automatic. Should be steady at something like 7:50. The fact that it is unsteady and high leads me to believe you have a vacuum leak somewhere.

Other culprits for driveability issues are the ECTS ( 2 wire in head; yours also has a single wire that drives the temp guage on the dash). At some point during the life of the car, it should have been replaced with an all brass sensor and the pigtail connector for it should also have been replaced. If this has not been done, use only AC Delco or Delphi parts sourced from a GM dealer or RockAuto or similar. Aftermarket sensors are not calibrated specifically for a Saturn. Sometimes they work sometimes they don't. Just avoid the whole mess and use GM parts.

If you have never replaced the front O2 sensor, this is another area for concern as the air fuel mix is controlled by the ects and the front oxygen sensor. If the reading on the front oxygen sensor is Goofy because the sensor has been poisoned by the exhaust it will not read high enough oxygen reading which richen in the mixture. In most cases so will a bad ECTS.

When I see funny things with the tach and the car stalling, it often turns out to be related to the EGR valve. If you have never cleaned it, it is certainly gunked up with carbon and is likely not fully opening or fully closing which causes weird things to happen.

Before you spend any money on the parts read the codes post the numbers here and I will help you.

Will do man, thx a lot!!

Any progress to report?

I have yet to get it scanned cuz I can't find anyone with an obd1. Though when I unhooked my battery to replace my starter, I hooked the battery back up and I haven't had any severe or constant problems with it like I did before. Idk if that may have helped it or not but it's not to much of a problem anymore.

You don't need a scanner. Find the port under the steering wheel or in the knee area under the dash that looks like it takes a plug of some kind. Once you find it, take a paper clip and bend it into a U shape that'll fit the top right two holes. Stick the paper clip into both of those holes and turn the key to the start position. DO NOT CRANK THE CAR. Watch the check engine light and if there are any engine codes, they'll start flashing. Each code will flash 3 times and then proceed to the next one. For example, a code 26 will flash the light 2 time, pause and then 6 times. It will do this 3 times and then move to the next code. When it's done, you should either get a code 12 or 55, IIRC. Quit looking for an OBD1 scanner. I doubt that you'll ever find someone that has one nowadays. Post back what happens.

You didn't mention starting issues that seemed starter related.i also mentioned the paperclip method on my post above.

Cost: 1 paperclip, 15 min max

Well, if you do ever want to know how to properly diag your car, you have the info

I greatly appreciate your help my friend! If I need any more advice I think you'll be the one I message first!! And again thanks!