The Saturn SW2 from hell :)

A while back I bought a ‘new everything’ Saturn SW2 (from my bro-in-law, who’s a mechanic, so I trusted the car would be a good purchase). Engine ringed, cylinders re-surfaced, top re-machined… New spark plugs, new spark plug wires, a new ‘old’ ignition module that worked fine in a different car, new serpentine belt, alternator checked, new battery, new exhaust…

So, on to my trouble. The car misses a lot while running. Twice, shifting from fourth to fifth gear on the highway, the car died completely and started again once I popped the clutch in fifth gear.

Both while accelerating mildly, which I do 95% of the time, and at constant speed, the car hesitates. It’s like the engine dies ‘a little’ about twice every second, and it does this perpetually.

The only time it doesn’t do it is during full acceleration. Right now, the only way I can drive the car on the highway is in fourth gear; doing about 4,500rpm because the engine rotates fast enough that I don’t notice the problem as much. It becomes more of a vibration instead of a constant jerking or tugging. It literally feels as though somebody has a rope around the hitch and pulls from behind.

Facts: It gets worse when humidity is high. Oil gets black within 500 miles of an oil change (Kendall synthetic). Car is a 1996 Saturn SW2 with 125,000 miles on the odometer. The car sat for two years before my brother in law renovated it.

I still remember the day I got it from him, it was like a new car. Except it hasn’t run right since. There has always been some kind of problem with it, and I’m about to loose patience with my relative. He wants to help, but I’m starting to think he can’t. He’s been swapping parts and trying to fix this for a year on and off. He is a trained Saturn mechanic with several years (ten) experience.

Is the Check Engine light (CEL) on? Does it even glow at start up as a self test? There are lots of diagnostic testing that can help narrow down the problem, and the computer should run some of them on it own. Running this bad should set a Diagnostic Trouble Code (DTC), and turn the CEL on. Have the codes read.

That being said, you could be running rich, maybe due to a leaking injector. Once the car is warmed up, possibly after a drive where it has been acting up, smell the exhaust. If it smells gassy, it is running rich. Pull the spark plugs one at a time. The one that is sooty black is the cylinder running rich. If they all look that way, have the fuel pressure checked. The regulator might be bad. If the fuel pressure is too high, too much fuel gets squirted into the cylinders on each cycle. The computer on this car doesn’t monitor or control the fuel pressure, so there is no DTC for it.

Thank you for taking time! I appreciate it a lot.

No Check Engine Light. I’ll check to see if the self test happens or not.

I’m sorry, I forgot to mention one thing:

This only happens to the engine when it’s warm. It runs really well when it’s cold, and I’d imagine that’s because the fuel mixture is different when it’s cold, correct?

I will do the tests you’re recommending, especially putting the diagnostic tool on it.

It sounds as though the voltage at the spark plugs is not strong enough. The plugs seem to ignite the richer mixture when the car is cold, but can’t ignite a leaner mixture when the car is warmed up. When you say that it gets worse under high humidity conditions, it seems as though something is bleeding off the high voltage that would normally get to the spark plugs.

I was going to suggest that since the car sat for two years, the gasoline tank may have rust or sediment. However, that isn’t consistent with the problem becoming worse under high humidity conditions.

The high voltage would include the plugs, wires, and the ignition module, correct? (I don’t know much about cars, I’m trying to educate myself here :), but it looks as though there are two transformers on the module, and it has rust on it. It tested fine in a different Saturn SL with the same engine type.)

What other parts could be affected in the high voltage chain?

Thank you very much for taking time!

Maybe someone else can help you out on this one. I’m from the breaker point distributor days. I remembered having a similar problem on my 1954 Buick and the car wasn’t getting adequate spark. I had the ignition system hooked to a scope to locate the problem. That is why made the suggestion about your car. I assume that a scope could be hooked up to your engine and the screen would display the voltage going to the plugs. This would be a step to take before throwing more parts at the car.

That’s what I’m trying to achieve, yes. It’s like you read my mind! I’m tired of throwing good money after bad money, and swapping parts has become the standard for ‘fixing’ cars it seems. Not a whole lot of fixing going on. That’s dangerous, because knowledge of how things actually work (or don’t work) is lost.
I see the same thing in my field of business, HVAC…

Thanks again,

  • Thom