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96 Saturn SL2 - High Revs, Clicking Temp, Clunking

I need some guidance on what to do next.
My 96 Saturn SL2 all of a sudden, out of nowhere, started having serious issues. I’ve had to be towed home twice because of this.
It is revving slightly high all the time when the clutch is in (around 1500-2000 RPMs), but after about 30 minutes of driving the temp gauge on the dash board clicks slightly up then slightly back down (not dropping or anything, just a slight click that is audible) affecting my RPMs which then jump. The jumping will get so bad within a matter of minutes that my car is clunking hard down the road. At this point, putting the clutch in revs the engine up to 3500-4000 RPMs. The weirdest part? After clunking along for a couple of minutes, the ABS light will pop on.
I just want to reiterate - the clunking is pretty violent and nonstop. The temp is clicking and the RPMs are jumping from 4000 back down to 0 with it IN GEAR causing the car to jolt continuously.
Once the car was off, it smelled terrible, too, like an electrical fire or burning brakes.
I read about a common issue in older Saturns having a revving issue, so we cleaned the throttle body, replaced the idle air control sensor and throttle position sensor, and it is still having issues. Looking at the engine it looks like everything is in great shape - had a tune up about a year ago including a replacement of battery and alternator, all of the hoses look great, and all fluids are full.
Here are the next steps I imagine doing:

  • just bought a pack of incense. Planning on seeing if there are any vacuum leaks the old fashioned way.
  • Check the coolant relay.
  • Check the engine coolant temperature sensor.
    These are my only guesses on what else it could be. I really need this car, can’t afford a new one, and am willing to do any work on it that’s needed (by myself). Any thoughts? I’m assuming it’s something electrical causing serious mechanical issues, and likely related to the temp of the car (since it takes 30 minutes for it to happen, and is related to the jumping of the dash temp gauge).

Like you, I’m suspicious of an electrical problem. The ECM (computer) requires a certain voltage to power it, and if it doesn’t receive that voltage, but still something close to it, it confuses the ECM to no end and pretty much anything at that point can happen. It’s like in that condition the car would behave like an Alzheimer’s patient in other words.

If you are DIY’er inclined, clean the battery terminals. If that doesn’t fix it, you’ll have to take it to a shop where they have the tools to measure the voltage and how “clean” it is at the ECM power connector.

The coolant temp sensor does, in fact, provide an input to the ECU which becomes a part of the algorithm that controls the idle, and in your car the ECU may drive the temp sensor as well (you’ll have to look up a schematic to verify this), and the ECU does not verify against any other input (so if it’s bad the ECU will never know and will not store a fault code), so I think checking the temp sensor output is an excellent place to start.

Pay some attention to the cooling system too. If you’re generating an air bubble around the temp sensor when the engine is hot, it won’t be sending out a proper signal, and that COULD be the root cause of your problems. Pressure check the system and check to see if there’s any evidence of hydrocarbons getting into the coolant. These engines are known for headgasket problems when they get older and a combustion chamber blowing hot gasses into the water jacket could easily be creating an air bubble around the sensor.

I’m also going to suggest that the noises, the RPMs jumping up and down, and the burning smell may be the engine severely overheating and binding up as it tries to run. I suggest that you not run this engine until you thoroughly evaluate it for the possibility of a headgasket breech and evaluate its cooling system. If I’m right, you already have internal damage, but you may still get some use out of the engine IF you repair it. I hope I’m wrong.

The vacuum check is an excellent step as well.

Post back and keep us informed. I, for one, would love to help you solve this one. If you need suggestions for doing the suggested testing, please say so and I’ll be happy to help. I’d normally post them up-front, but you sound like you’re already headed down the right path. You sound like you already have some basic knowledge.

I plan to keep checking back here because you gave me some great ideas on where to go to from here. Replaced the engine coolant temp sensor and it made no difference.

Slight change occurred randomly in the past week - now when putting the clutch in the RPMs are dropping like normal instead of shooting up. At stop the RPMs are still staying at about 1500, then dropping down when my speed hits 0. It has a strange, rough idle hovering/fluctuating between 900 and 1100 RPMs. I am not driving it enough to get it up to operating temp again until I fix this. I don’t want to do any permanent damage to the engine (hopefully I haven’t already).

Planning on cleaning the EGR valve tomorrow and seeing what state it’s in. Head gasket is something I will look further into - I found some quick and painless tests on wikipedia for external/internal leaks that I will do. It does look like it may be a little “frothy” in the coolant tank with some grayish froth around the edges. I may need to look into that further. For now there is no smoke of any color coming out of either the engine or the exhaust pipe. As an aside… In the past year we have replaced the battery, alternator, O2 sensor, spark plugs and wires - so I’m assuming it isn’t an issue with any of those.

Saturn’s are notorious for having issues with the ETC sensor and the connector that goes to it. Usually you have to replace both the sensor and the connector, and it HAS to be a GM OEM replacement, aftermarket sensors don’t seem to work at all.

There is another issue that plagued the 00-02 SL1 engines and that was the intake manifold gasket. The design on the SL1 engine is very weak around the #1 cylinder and in 00, they went to a cloth gasket instead of a metal backed gasket and it would fail regularly.

I have not heard of this issue being so common on the earlier SL1 engines, though it would happen on high mileage engines occasionally. I have not heard of any issues with this on the SL2 engine but some of your idling issues are symptomatic of the intake manifold gasket or other vacuum leak.

These engines are not prone to blowing the head gasket unless severely overheated, but it can happen if the coolant gets way too old. The frothy coolant is worry some though. I’d start with a genuine GM ECT sensor and connector first.

Keith, I think you’re on the right track here. Frustrating day, just had to be towed home after getting a diagnostic at the mechanic. Had an issue with the throttle position sensor (we somehow didn’t install it correctly, didn’t twist it on just popped it on) so fixing that fixed the rough idle. It was driving great so we hoped it was fine, but after warming up the car it clunked again. Called a tow so I don’t risk further wear on the engine mount.
Diagnostics told us to do two other things. First, we hadn’t yet flushed the coolant or replaced the thermostat. Coolant is “cloudy”.
But they also mentioned the intake manifold gasket. There is so much oil in my spark plug wells that it is going up to the rims of the spark plugs. They said fixing the gasket should help with the leaking oil. I also installed Bosch spark plugs and they told me to never use those because they aren’t made well for my car (but he said they are firing well, surprisingly). So I plan to replace the gasket (which is fairly easy to do in Saturns) and replace spark plugs and wires (I will use ACDelco).

I had that wrong. The intake manifold isn’t leaking. it’s the valve cover gasket.

Leaky valve cover gaskets are a pretty common source of oil leaks. Usually not very difficult to fix.

Don’t “flush” the cooling system, especially do not use any chemical flushes on a Saturn, that is asking for trouble. Just drain the coolant from the radiator and the block. The block drain is just under the lower radiator hose, but if you are going to replace the thermostat, you will be removing this hose anyway.

You can stick a garden hose in the upper radiator hose with the thermostat out to flush the block, but I do not recommend it. I prefer to just drain the whole system and refill with fresh coolant mixed either 50/50 with distilled water, premix (already diluted to 50/50 with purified water) or my favorite of 2:1 antifreeze to distilled water. Any residual old coolant will actually have less contaminates in it that tap water.

If your current coolant is dexcool (pink or orange), either stay with it or use one of the new universal long life coolants. Don’t use the old green stuff.

If the spark plug is the right heat range and the proper tip length, it is not the wrong plug, regardless of who makes it, but I do prefer NGK, although my Saturn has double platinum Champion Spark Plugs that currently have about 90k on them and they haven’t missed yet.

Not sure how you “twist on” the TPS, that doesn’t make sense to me. I also do not understand how diagnostics came up with cloudy coolant, there isn’t a code for that that I know of. That would be a visual. What diagnostics did you have done? What were the actual codes, I don’t want the mechanics interpretation, I want the actual code number like P0116 etc.

Could you better describe the “clunk”?