1995 Saturn SC1 Irregular Downshift

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ELEMENTKNG20
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Hi, I have a 1995 Saturn SC1 SOHC. Just recently I was driving to the movies and I came to a stop light.
Normally when I brake it downshifts from two to one,
then idles normally just below one. When I came to
that stop light it downshifted from one to one and a
half, then idled at one. This didn't feel normal and
ever since that night it keeps downshifting below one.
Is this normal? Or is it suppose to shift above one
and just below 2? Basically it downshifts harder than
usual. I did a tune-up because I thought that was the
problem, but after I did that it still downshifted
irregularly. The performance button is not on, its set
to NORMAL. It shifts normally when driving, its only
when I come to brake is when it acts up and downshifts lower than one. Could the transmission be going? It feels like it surges down below one, then it idles fine. Any thoughts? Also a new alternator and battery were replaced, along with new belt and tensioner.
Mar 19, 2006 at 11:51 AM
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PEPPERMRJ
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How many miles? What other maintenece has been done? Satty's automatic transmissions should have the fluid and filter changed every 30,000 miles. Use OEM filters only.

I'm not sure I am following your post right. Are you saying that the downshifts occur at certain RPMs that you mention?

Post back. :)
Mar 19, 2006 at 12:42 PM
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ELEMENTKNG20
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OK, 87,400 miles exactly. Just hit it tonight. It was serviced July 2005, and has not been checked ever since. I tuned it up earlier today to try and fix the surging downshift. but to no luck didn't fix it. To answer your question about my last post, it surges a little when downshifting. Normally it downshifts from 2,000 RPM to 1,000 RPM when braking. Last night when I was braking it downshifted 1,500 RPM to 1,000 RPM then surged down to about 500 RPM, then back up to 1,000 RPM. I idled normally at 1,000 RPMs. Also when I start the car it used to rev up to 2,000 RPM, now it only goes to 1,500 RPM. I don't know what the problem is. Also...it may be that the transmission was never serviced since the car was purchased in 1995. :?
Mar 19, 2006 at 12:51 PM
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PEPPERMRJ
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I would definitely service the trans. It is easy and inexpensivto do. Use only a Saturn factory spin on tranny filter. There will be a donut shaped magnet inside the filter that you can clean and reuse with the factory filter. Aftermarket filters have a different hole patern that don't work well with the magnet. It is not necessary to keep it by why not. Also the tranny only requires about 6 or 7 quarts of fliud during a change. The bad part is you must use mobile 1 synthetic fluid. Pricey but woth every penny.

Next issue. Your flutuating idle may be caused by a bad ECTS (engine coolant temperature sensor). The original sensors had composite/plastic tips. They will crack at some point in time. When they do, they can leak coolant onto the wire connector of the sensor. this should be inspected, cleaned, or replaced.
A bad ECTS can cause RPM surges, poor fuel economy, erratic tranny shifts, hard starting, and even no starting.
Has the ECTS ever been updated to the all brass tip design from Saturn?

Good luck and let us know. :)
Mar 19, 2006 at 1:08 PM
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ELEMENTKNG20
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Nope nothing has been changed to my knowledge. I should def get this checked out. I have fixed most of the problems with my car but this might better for a certifiet tech to fix it, ex (STS, PepBoys) DO you think this would be pricey? And would they fix all the issues you explained? How much do you think it will cost? Also with the cracked tips, do you think this is why my engine quickly heats up? During the summer when idling it heats up fast. What may cause this?
Mar 19, 2006 at 1:15 PM
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PEPPERMRJ
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It is no harder to replace the ECTS than to replace a spark plug. Do it yourself. The part from Saturn should be under $20.00. Get the tranny filter while your there.

See https://www.2carpros.com/forum/saturn-sc-1-1995-vt4925.html for installation instructions.
Mar 19, 2006 at 1:22 PM
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PEPPERMRJ
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Where you located and how fast is fast for the engine heating up? My 96 runs at about 1/2 on the temp gauge. The fan kicks on at about 3/4 and goes off at 5/8ths.

The ECTS will help a variety of engine issues. It is something that will fail. It is only a matter of when. Replace it first and deal with any other issues as needed.
Mar 19, 2006 at 1:28 PM
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ELEMENTKNG20
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Thank you for the information, I will let you know how this turns out...one more question though. The engine heats up fast during the summer. Normally the coolant temp gauge is set normally between 1/4 and It usually never goes past the half mark. Is my fan suppose to turn on when it heats up fast? also, it starts to surge below 1,000 RPM when it gets to the half mark. Is this is ECTS?
Mar 19, 2006 at 1:31 PM
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PEPPERMRJ
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The coolant temp gauge is actually controlled by a different sensor that feeds only the gauge. It is explained in the link I posted earlier in this thread.

The cooling fan should come on at a predetermined temperature. It is controlled by the cars computer and the ECTS. It will aslo come on with the AC if it is working properly.

The surging could be caused by the ECTS. It could also be other issues. My advice is to replace it with the updated brass tipped sensor from Saturn first. It will fail, only a matter of when. Once that is ruled out as a cause you will be able to diagnose any other issues much more simply if need be.

Surging can also be caused by low fuel pressure, a malfunctioning IAC valve, and a few other items. None of which are common problems on Saturns like the ECTS is.
Mar 19, 2006 at 1:55 PM
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ELEMENTKNG20
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OK, thanks again, I will message you when I get these things figured out. Either way I will let you know how it went. Thanks again for the VERY USEFUL information. :)
Mar 19, 2006 at 1:57 PM
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Suggested Repair

Service the automatic transmission with a Saturn factory spin-on filter and about 6-7 quarts of Mobil 1 synthetic fluid, since fluid and filter service may never have been done. Also replace the engine coolant temperature sensor with Saturn's updated brass-tipped sensor first; a cracked original plastic-tip sensor commonly causes RPM surges, erratic shifts, and idle problems. If surging continues, then check less common causes such as low fuel pressure or a faulty IAC valve. The temperature gauge uses a separate sensor; the cooling fan is controlled by the computer and the ECTS.

Conversation Summary

The owner of a 1995 Saturn SC1 with about 87,400 miles reported harder, irregular downshifts and RPM surge only when braking, plus a lower cold-start rev and faster summer warm-up. Driving shifts were normal, a tune-up did not help, and the transmission may not have been serviced since 1995. The expert recommended an OEM filter and Mobil 1 fluid service and replacing the ECTS with the brass-tip sensor first, noting that a failing ECTS often causes surges and erratic shifts. Fan operation is computer and ECTS controlled, while the gauge uses a different sensor.

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