Hesitation on acceleration
 

Hi, my name is zach and i recently bought a 2000 saturn sl2. Like ive heard about with these cars, mine has a stumble on initial acceleration but is fine once it is moving. What i have noticed is that there is no hesitation until the temp gauge gets to the 1/4 mark and as soon as it hits that it starts to stumble.
I recently changed the plugs and wiress, used ngk v power gapped at .040. The hesitation is still there but not as awful. Any suggestions? I checked the wires and the no 1 and no 4 plug wires are not mixed up. The only thing i know is that the motor was recently rebuilt (burnt valves) so it has all new gaskets and such. Any help is greatly appreciated. Last thing is that my ses light is on and last time i had it cleared it was saying the idle air control code. Came on again and havent had it read yet.

Moved to SLx section. No tech questions in the New Member Area please.

Please get the codes read and post them here as Pxxxx, not the description of the codes.

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Best plugs to use for this engine are the stock ones it left the factory with:

NGK NG5643 Copper Plugs, also known as NGK BKR5ESA-11 gapped at .040.
Simple, reliable, and concluded by 8 zillion people looking for a better plug to be best.
Ignition system likes it. Ignition system expects it -- not platinum, not iridium, not any exoticum.

Not sure about the "Like I've heard about with these cars" part. I've logged almost 500K on two mid 90's Saturn SC2s, and the few times they stumbled repeatedly, I figured out why and addressed it. A properly maintained S Series car runs and accelerates smoothly.

1) Try cleaning the throttle body w Throttle body cleaner (not carb cleaner). Be sure to get the back of the throttle plate clean. Pay particular attention to the small hole (inside the throttle body bore) near the throttle body entrance (in the bottom).

Work the throttle by hand from under the hood while spraying; you will need to give it extra gas as it will try to stall when you're spraying.

The way to thoroughly clean it is to remove it from the car.

Other possibilities but no need to jump the gun.

Manual/Auto?

Does it idle smoothly and at what RPM?

Reply to hesitation
 

It idles normal around 900 rpm, its an automatic and it has 186k on the body but around 40k on the motor. Ill get the codes read and will post them. Ipl try the throttle body cleani ng and see if that helps

The idle speed for a DOHC Automatic in Drive w A/C off is 700-800, so you're running a bit high. This could result from a number of factors, so I won't start guessing until we get the codes back.

Definitely try the throttle body cleaning and pay attention to the passageway at the bottom --it's the idle air control valve

Hesitation on acceleration
 

Sorry, but for some reason it will not let me reply to comments on my post so here goes again. I have a 2000 saturn sl2 automatic. 186k miles on body and around 40k miles on rebuikt motor. Car has hesitation on initial acceleration. I have changed the plugs and wires, no 1 and no 4 cyl are not mixed up. I have cleaned the throttle body. Only code that as showing was po442 and i cleared it. Any help is greatly appreciated. My number is 6363850241 as texting would be a bit easier as to help me troubleshoot. Thank you and happy mothers day

Response to your answer
 

The only code that popped up was po442 evaporitve canister leak. I cleaned the throttle body thoroughly and that did absolutely nothing. Car shifts rough too come to think of it, it bucks and it reminds me of my stealth, but that turned out to be a fried computer

Merged your threads. Not sure what was going on with that, but fixed now.


Have you ever changed the ECTS (Engine Coolant Temp Sensor)? Original design was resin tipped and failed, leading to bogus temp readings and overly rich A/F mixes.

Replace with a GM sourced brass tipped ECTS and replace the connector at the same time About $50. Solder n shrinkwrap.

Not every part on a car needs the OEM replacement. The ECTS on a Saturn S car DOES.

Generics from AutoShmo do not behave the same (resistance vs temp response)
and this is what leads to incorrect A/F mix issues.

When a Saturn S series ECTS fails it usually fails open circuit, which is the equivalent of -40 deg as interpreted by the PCM. Since the ECTS V drop Value measured by the PCM never changes, the car runs absurdly rich and as the car warms up and goes into closed loop operation, this can lead to driveability issues since the A/F mix should be getting tweaked by the Front O2 sensor readings and the coolant temp, but it's just sitting there as though it is -40C.

One of the driveability issues seems to be a stumble or hesitation around 2K rpm. Not the only one, but has been reported by many owners. Bad ECTS can lead from everything to driveability issues, starting issues when cold, starting issues when hot, cooling fan not coming on when coolant temp rises (because the PCM thinks the coolant is at -40 so it never requests the fan on) and eventual overheating...etc

Since throttle body cleaning didn't help at all (surprised), ECTS is next recommended step as it cures many subtle and not so subtle issues and prevents many others down the road. the engine w 40K was obviously rebuilt, but only a Saturn dude would know the ECTS issues.

As for P0442 Small Evap Leak detected:

Ensure gas cap is tightly sealed and clean around the mating surface. You can use a TINY bit of vaseline on the o-ring in the cap to restore its ability to flex.
Get the code cleared and see if it comes back.

Also
Check that the vacuum line from the intake to the purge solenoid is connected.
Check that the line from the purge solenoid to the canister is connected.

High idle, we'll wait on the outcome of the above.

I read about that somewhere else how the ects's were faulty from the plant. As for the motor it was pulled from a totalled saturn with 40k orig miles yet somehow the previous owner managed to burn up a valve so the motor was rebuilt. I will definately replace that as the symptoms you described are what my car does, it will overheat if it sits because the fan doesnt always come on. Can i get that ects through a gm dealer?

indeed you can---must be an original resin tipped ECTS in there.
Surprised no one grabbed up such a low mileage engine before you unless it just hit the lot.

You'll be happy you did. And REPLACE the CONNECTOR. It costs more than the sensor and it seems stupid, but when the resin tipped ones go bad, they often leak right up the center of the sensor and onto the connector, which then corrodes, adding resistance to the circuit and screwing up the PCM's temp measurement.


Try a Chevy dealership first. They seem to have a clue as to what you're asking for.
Lemme go look up the GM part number and I'll edit this thread

GM part Number 21025106 (Believe it is AC/Delco) about $11 online--this may be listed as an AIR CHARGE temp sensor. The car does have one. It is the IDENTICAL PART. If you have to you can ask him for the 2 wire ECTS --it should be the identical part number but you never know.

Forgot -- I think someone makes an aftermarket connector harness for this (FINALLY)

Dorman 645-900 --but theirs is near $30 at Advanced and the dealer is not that much more. Or is it.?

Call and get a quote. The dorman harness should be fine

Remember -- it's a SQUEEZE connector

I really appreciate it man, i bought the car as a commuted cause my 83 elcamino gets about 8 mpg lol. Ive never owned a saturn but ive heard of their renowned reliability although i will say they have some reall junky interiors lol. I plan to do a tranny flush soon, and a couple mods to make it more to my liking. Out of curiousity, is there any safe way to crank up th e power of the 1.9 without damaging the motor or tranny?

power? Turbo. But alot of fab is required and the parts needed to do it are getting harder to find. You can do this on a 40K engine but not advisable on a 186K auto tranny. You'd want a 5 speed swapped in to enjoy it.

Plus if it's a 186K tranny, count your blessings that you have no reverse slam, slamming into gears, missing 2nd gear, loose input shaft nut, yalvebody/solenoid issues, no reverse at all, etc.

The person you bought it from should have had some or all of those tranny issues.
Might be why they sold it. But fixed it first.

Updated parts numbers above

Honestly there is no record of tranny work done to the car. I have ever record, oil change, reciept, everything for this car including original window sticker. They never reported any tranny problems. It shifts good, but i think one of the motor mounts is bad/loose.

torque axis (top mount) --if they never changed it EVER it is gone. They are semi consumables on the s cars if you own them long enough

Another part where OEM makes all the difference. Reduced vibrations in the cabin = less cheap plastic rattling.

While you're at the dealership, get an upper torque axis mount. Be SURE he has the year correct as they kept changing the design and the hole patterns, so not all mounts will fit all years.

Also get a set of 3 new mounting studs and bolts and use a torque wrench or you WILL twist these off.

During replacement, after supporting the oil pan with a WIDE sheet of plywood to keep from denting the oil pan from applying pressure all in one spot, loosen the lower torque axis mounting bolts, then install the new upper mount, torque down, THEN tighten the lower torque axis mounting bolts, then put the car back on the ground and enjoy your quiet new ride.

The only other mount that usually causes troubles is the tranny mount, It can be changed in your garage but if it isn't causing problems, leave it alone

Still has hesitation
 

So after replacing the ects and the wire bundle for it the car still has the exact same hesitation. Next guess is fuel injectors. Pcv valve is working, car is showing correct temp on obd2 reader. Does not cut out when screaming down the highway so fuel filter is ruled out along with fuel pump. Idles normally. Any more ideas? Thanks

It may idle smoothly but the idle is too high. This is usually indicative of a vacuum leak. In your case, a small one, but a vac leak nonetheless.

I would spray down around the intake manifold ports to the cylinders, around where the throttle body meets the intake, and around all vac lines.

Per your P0442
Be sure to carefully inspect and spray down the vacuum line from the intake to the purge solenoid. COULD be the cause of your slightly high idle and MIGHT correct initial accel issues since if it is a vac leak, there is unmetered air sneaking into the manifold and messing up the A/F mix near idle.

I am surprised there is no difference in performance w the new ECTS.....

I dont think its a vacuum leak because that code has not come back since i reset it, and also when the motor was rebuilt it had all new gaskets including the intake manifold gasket and was sprayed down to check for that. We think it is a fuel injector stuck open because the o2 sensor is reading weird going from high to low, so the thought is that one of the injectors might be stuck open causing the car to run fat and the computer doesnt know how to compensate. My buddy has a tuning device on his computer we are going to use and seewhat the injectors are readi ng along with fuel pressure. My only rhought on the ects is if it was broke. Wouldnt the temp gauge not work?

EVAP system codes take a while to reset because meeting the somewhat obscure criteria for the different EVAP I/M tests to run is a PITA. If you check the EVAP I/M w your scanner, I pretty much guarantee it will say Not Ready, because not all the EVAP tests have been run.

If your injector was stuck open, the PCM would
---keep leaning out the mixture (shrinking the open window for the injectors) until it either succeeded in getting the front O2 readings in the correct range.
---keep leaning out the mix until it reached its preprogrammed adjustment limit -- at which time the PCM would throw a EDIT: RICH code. And that's not occurring.

A bottle of techron fuel system cleaner can't hurt for the next step. The injectors could be gunked up. Worked wonders for my 97 SC2 when it was getting sluggish.

The fuel pressure can easily be read w a gauge from the port on the fuel line that is under the hood.

If the ECTS was completely defective, I doubt the gauge would work, and I doubt the car would run well at all.

Read the resistance ice cold (include ambient temp)
Read the resistance at operating temp.
Post here and we'll double check.

You can look up the GM drive cycle as well as 300 posts regarding "can't get EVAP monitor test to run" for further information.

As far as vac leaks, it can't hurt to check and costs almost nothing.
As far as fuel system cleaner, less than 10 bucks

There is also a slim possibility that the Throttle Position Sensor is not behaving as designed. Meaning that the V vs % throttle behavior is either inconsistent or has "dead spots" or rough spots where the V does not smoothly change but instead jumps in a certain throttle % range.

This would be a good one to check with the scan tool and compare to expected values (which I can dig up).
In your case, I would be looking for barely off idle V fluctuations with increasing % throttle instead of the expected smooth V transitions.
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I'm not a parts shotgunner and I will not recommend changing anything I can not reasonably expect to be the cause of a problem as determined by testing. Hence the testing first, then the conclusion and next steps.

This may increase the overall diag and solution time, but for us DIYers, it is still a hell of a lot cheaper w no labor costs and judicious replacement of components