INGO Mechanics

[A 7.62 Exodus]

Calling all mechanics/car savvy people. I'm having some issues with my car. They're livable, but rather annoying at this point. My question to you is, what can cause RPM fluctuations in a car? More info:

Car: 2001 Saturn SL series

Here are the problems. Many times after running for a period of time, and shutting the engine off, I have to give it gas to start it again (grocery runs)

When the car DOES start, the RPMs shoot up to roughly 2300. That's comparable to me going 75 down the highway. Same thing when I put it in park. The RPMs shoot to around 2000, then back down to my standard idle of about 1200-1300. However, one time I put it in park, and it stayed idling at over 2000 RPMs

Sometimes when I put the car in gear (automatic), I'll lose RPMs. One time, I was idling at 1300, and when I put it in reverse, it fell to like 400-500 RPM before shooting back up.

I have one semester of school left, and was hoping to pay off my loans before I began car searching. So tell me, should I start saving for a new car? Or might this be something fixable?

EDIT: Spark plugs just changed by a pro

 

[CathyInBlue]

Could me engine speed sensor (generally a hall effect sensor on the camshaft) going bad, but I'd expect that to throw a massive computer code. If the computer thinks it's going faster than it is, it could retard the spark/throttle to bring it back down, resulting in very low RPM, or thinks it's going slower than it is, resulting in advanced spark/throttle, resulting in high RPM.

 

[Bigtanker]

Throttle position sensor.

 

[saleen4971]

What motor?

Typically a crank sensor will fail, or cause random sputtering.

Since it is a gm product, I would always check for vacuum leaks - specifically at the intake manifold. Are you low on oil or coolant?

Actually, I don't think those have coolant in the intake. Still, take some brake or carb cleaner and spray every vacuum connection, including intake to head surface.

Iirc a fairly common issue with them is the next and/or pigtail. A coolant temp sender can cause idle issues, AMD is relatively cheap. I would replace the ext and pigtail if for nothing more than a precaution.

Also wouldn't hurt to check and clean your IAC and egr valves, although a hit soak issue sounds more like an IAC or ext - get would usually have the same issue at the same temp, not necessarily only after a hot soak/start

 

[A 7.62 Exodus]

What motor?

Typically a crank sensor will fail, or cause random sputtering.

Since it is a gm product, I would always check for vacuum leaks - specifically at the intake manifold. Are you low on oil or coolant?

Actually, I don't think those have coolant in the intake. Still, take some brake or carb cleaner and spray every vacuum connection, including intake to head surface.

Iirc a fairly common issue with them is the next and/or pigtail. A coolant temp sender can cause idle issues, AMD is relatively cheap. I would replace the ext and pigtail if for nothing more than a precaution.

Also wouldn't hurt to check and clean your IAC and egr valves, although a hit soak issue sounds more like an IAC or ext - get would usually have the same issue at the same temp, not necessarily only after a hot soak/start

4 cylinder, 2.0 L, twin cam if I'm not mistaken. It's a 4 cylinder, 2.0 L for sure though

 

[A 7.62 Exodus]

Throttle position sensor.

Would this effect the start up issues I'm having as well?

 

[Moparracer89]

Would this effect the start up issues I'm having as well?

Yes. The computer doesnt know where the throttle blade is and is hunting for a signal (revs up)

 

[halfmileharry]

Do you have a check engine light on? Have the codes scanned. Lots of guessing without hands on.
IF it's not throwing codes I'd sure be looking at vacuum leaks.
Also, do you have exhaust leaks? IF exhaust is leaking you can possibly get fuel mixture irregularities as the readings fluctuate from too much oxygen in the burnt fuel exhaust.

 

[A 7.62 Exodus]

Do you have a check engine light on? Have the codes scanned. Lots of guessing without hands on.
IF it's not throwing codes I'd sure be looking at vacuum leaks.
Also, do you have exhaust leaks? IF exhaust is leaking you can possibly get fuel mixture irregularities as the readings fluctuate from too much oxygen in the burnt fuel exhaust.

No check engine light, no codes. When I took my car to my mechanic to get the plugs changed, they scanned the crap out of that thing. I found a saturn forum that says the ETCS sensor is also a problem. My spring break is in three weeks. I plan on replacing the ETCS, and the throttle control sensor. It's a whopping $40 dollars in parts, and a few hours of labor

Also, how can I tell is my exhaust is leaking? I feel like I can answer your question, I just need a little more info into what I'm looking for

 

[K_W]

1200-1300 is too high of an idle. I vote vacuum leak.

 

[Thegeek]

For things like this, I'd take it to the dealer and pay the $90 for the diagnostic. Even if it's not throwing a code, they'll be able to tell you where the bad ECU data is coming from. In my experience, it's $90 of insurance to make sure you don't spend your money and time on the wrong thing.

 

[Stschil]

With all the electronics cars need to operate these days, it could be any number of issues, most of which have already been mentioned. One that I haven't seen is the MAF (Mass Air Flow) sensor which will be located somewhere between the air filter and the engine intake. A quick and dirty test: With the motor running at idle, use the butt end of a screwdriver and rap on the sensor, but don't hit it hard enough to crack the plastic case. If this changes the way the engine idles, its a pretty good bet that the MAF is going bad.

 

[GTM]

Throttle position sensor.

I'll second this. I have a 2002 Saturn SL and had to replace the TPS. It's an easy, 5 minute job.

 

[GTM]

Also, 2000-2002 Saturn SL's had a tendency to leak around the intake gasket, toward the passenger side of the intake. My did and it caused it to idle at 1500 rpm. You can test it by spraying carb cleaner around the area and listening/watching for the RPM's to increase.

 

[RustyHornet]

Might clean the throttle body while you're in there. I had a 3800 with a really carboned up tb and the valve was sticking a little causing weird problems like you're describing.

Jon

 

[gunsisgood]

With all the electronics cars need to operate these days, it could be any number of issues, most of which have already been mentioned.

Yep,
I have always felt that cars and trucks were Perfected from around 1965 to the early 70s,
down hill from that point on.
Sorry cant help you but I can feel your pain.

 

[halfmileharry]

No check engine light, no codes. When I took my car to my mechanic to get the plugs changed, they scanned the crap out of that thing. I found a saturn forum that says the ETCS sensor is also a problem. My spring break is in three weeks. I plan on replacing the ETCS, and the throttle control sensor. It's a whopping $40 dollars in parts, and a few hours of labor

Also, how can I tell is my exhaust is leaking? I feel like I can answer your question, I just need a little more info into what I'm looking for

IF your exhaust is leaking you'll hear it.

 

[RustyHornet]

Yep,
I have always felt that cars and trucks were Perfected from around 1965 to the early 70s,
down hill from that point on.
Sorry cant help you but I can feel your pain.

Working in a resotoration shop we talk about this all the time, but the general consensus is in a perfect world we would have the looks, style, character of the old ones with modern running gear... While the new ones have become more complicated they are far more reliable than the old ones were, that's not to say the old ones were not reliable.

Just came up the other day as my boss and I went on a road trip to drop off all the chrome for a 1956 Buick, I was not fortunate enough to be around when the old cars were being driven daily but he was, he said it's amazing the cars nowadays just seem to run forever hardly ever see them on the side of the road. Unfortunately if you're modern car does break down its almost 100% likely you'll be calling a tow truck....

I myself prefer the old ones for their simplicity and if it weren't for other drivers, road salt and fuel prices, I'd be driving one everyday. The dumbest thing I've ever done, was last year my father and I took a road trip in a 1970 Lemans that we had only got running 2 weeks before and had been sitting 5 years without being driven, all original never been rebuilt, we did the basics to make sure it was safe. Drove that car from Fort Wayne to Wichita, Kansas for a Pontiac show. Did not have a single issue and made it back the same way. It may have been the dumbest thing I've ever done, but it sure was the most fun!

Jon

 

[PGRChaplain]

Vacuum Leak.