Hesitation while accelerating Saturn SL1

I have a 1995 Saturn SL1, SOHC, manual transaxle, with
145,000 Km (much on the hwy). I do change the engine oil frequently
5000Km, check fluids often, etc. In the past two
weeks, when accelerating, my car hesitates, it feels jumpy, or bucking/jerking.

To resolve a recent stalling problem at deceleration and low rpm <2000rpm,
I did the following:

- changed fuel filter
- cleaned carbon out of throttle body with carb cleaner (was
O2 sensor safe), and there was alot of carbon...
- replaced vacuum hose between throttle body and crank case, old one was
weak & almost ready to collapse. (fuel/PCV line hose 11/32" ID, 50 PSI)
-used STP concentrated fuel injector cleaner in gas tank.
-spark plugs were gapped & changed last summer.
-replace air filter

I don't think it is a slipping clutch, because the clutch feels fine and
grabs when I ease up on the clutch pedal when starting in 1st gear.
Although I feel this bucking in gears 1, 2, 3, not so much in
4/5....typically at lower rpm < 2500 rpm 1500 - 2200 rpm.

It could be the ...
-EGR valve
-ignition wires
-cap and rotor
-MAF/MAP sensor (where are these located?)

any suggestions?

Thanks, Roger

 

Very good post. You covered a lot to eliminate a bunch of questions we
here might of had to go through. I kinda suspect the EGR. It may not be
closing off, at least not very well do to carbon. Btw Saturns never used
cap and rotors.

 

Good. you might want to just remove and clean again to get EVERYTHING.
It's 2 10mm bolts and unplugging the cables. Really easy, at least on
the dual hamster models.

Maybe it did something. I don't trust those things though.

Good too.

*ding!*

Change those first. I bet the problem goes away. Mine was like this
too, i changed the wires - ran a LOT better. It just feels like it's
missing or hesitating every now and then, randomly? or, at low RPM, as
the RPM increases, it suddenly 'kicks in'?

None - it's a DIS system. A coil per plug.

No MAF. MAP is on the intake manifold. I'm not sure about the single
hamster motors, but the two hamster ones have it to the left end of the
manifold.

Replace the plug wires. Do it first. I bet it fixes it.

 

Thanks Philip & everyone

Ok here's some more observations....

Yesterday I did remove the EGR valve and there was much carbon in the
valve and pipe. I used Carburator cleaner (sensor safe) to try & clean it.
The valve seems to move/close more freely thereafter. I also
replaced the PCV valve (FRAM PV295).

However as I drove
to work this morning and the car still felt like it was stumbling when
accelerating. When gearing up from 1st to 2 & 3 my car hesitates, it feels
jumpy, or stumbles with a lurching/bucking. My sense is that it
seems like the clutch plate is slipping. However this symptom does not occur
consistently. Sometimes it drives/feels very well. But when it happens it
always does under lower rpm (1600-2500), typically as I am gearing up and
accelerating with the gas pedal. I do not notice this under high rpm >3000
rpm or when in gear 4 or 5 (maybe because of momentum). As I stated
before, I tested the clutch, easing up on the pedal into 1st gear from a
stationary position either on level ground or uphill, and the clutch does
grab. Then if I press the gas pedal once in gear sometimes the jerking
occurs. I cannot say that it appears to be a problem with the fuel pump.
It primes fine when I turn the key to ACC, and the engine does not seem to
sputter (like it's running out of gas). I'd suspect the clutch slipping if
it was consistent. As Philip suggested I'll change the ignition wires to
see if that does the trick (however when I changed the spark plugs last
summer I did also measure the Resistance on the wires and they were
fine). I would rather not spend money on changing the clutch plate or
fuel pump if it is not necessary as these are very expensive.

Thanks, Roger

Very good post. You covered a lot to eliminate a bunch of questions we
here might of had to go through. I kinda suspect the EGR. It may not be
closing off, at least not very well do to carbon. Btw Saturns never used
cap and rotors.

 

I experienced a hesitation while accelerating with my 1999 Saturn
SL1...then I started to notice a slight unusual sound. It ended up being
the TIMING CHAIN. I got it replaced and that problem is over. Dunno if
it's what you're problem is, but if it were, I would get it checked out.
As you know, when that chain goes, so does your car.

 

Resistance measurements aren't really that useful, and if the wires are
greater than 2 or 3 years old, they're suspect.

At the really high volages that ignition systems work at, you can get
interesting things even if the resistance checks OK, because the wire
insulation could break down at high voltage, etc. I've seen it with TV
sets a few times...

 

This matches the description as if you're driving on three cylinders,
intermittently, as most suspected. There's no safe way to check for
spark on the plugs or plug wires on DIS for DYIs, but perhaps one.
Hookup an induction timing light. At low rpm you can observe carefully
the consistent or inconsistent sparks. After finding the inconsistent
cylinder, swap the plugs and try again to rule out a bad plug. DO NOT
LEAN on the car's earth. At the really high voltages that ignition
systems work at, and for unknown reasons, you can get an interesting
shock that you'll remember a lifetime. I had my share.

 

A severe, but positive test for clutch slippage:
Put it in 3rd gear, aply the parking brake, and try to "take off".
Let the clutch out while revving the engine. The engine should die, even
before the clutch pedal is all the way up.

An even more brutal (but still more positive test) is to rev the engine to
above 3000 RPM, in third gear with the clutch pedal down, parking brake
applied. Without modulating the throttle, slowly let out the clutch. It
should slow and stall the engine, evenly and eventually. Any upward blips in
the engine speed could mean a worn throwout bearing, or weak dampener springs
in the clutch disk. More severe slippage will, of course, be more obvious.

Sounds more like weak spark on one or more cyls.
One or more coils are weak, or you have bad spark plug cables.

Take the car into a dark (I mean pitch-black) garage, run the engine at fast
idle, around 1800 RPM, and raise the hood. Look for any visible sparking,
corona discharge...

Ignition coils can also cause this symptom when they go bad.

 

Thanks everyone. But about the spark plug cables.....

I have noticed that the wire on cylinder 4 has a defective connector to
the plug itself, sometimes it does pop off....I have used pliers to try
and close the mating connector so that it is tighter. But I still suspect
it...so I'll get new cables (Niehoff brand - a-ok? good brand? I don't
need high performance cables, this car is a 1.9 L SOHC afterall ...)

A ? though, Would a misfiring plug feel different to the driver though? I
feel the car lurching as if it lost power momentarily... and this happens
only as I am gearing up, on level ground and up/downhill (any load to the
wheels). I notice it more when gearing up from 1 to 2 to 3. Sometimes the
car drives well though. I would think if a plug was misfiring the
vibration would be more from the engine itself. Considering the trouble I
had previously with lower rpm stalls, maybe I did not fully clean all the
carbon from the EGR valve (carb clnr). I did the best I could with the EGR
though. Maybe I should replace it also?????

--
Roger Ehrlich
Computer Science
Ryerson University, Toronto, Canada
**
"It is important that students bring a certain ragamuffin, barefoot,
irreverence to their studies; they are not here to worship what is known,
but to question it."
Jacob Bronowski, The Ascent of Man

"A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete fools."
Douglas Adams

 

I have a 1997 Saturn SL1. Two weeks after buying it used in 2000 I had
a terrible missfire. Got home, found a bad spark plug wire, change
them out and everything was okay for 3 years. Then about a year ago I
had the miss-fire with moderate throttle. I changed the plug and wires
and all was okay again until about 6 months ago. The car is fine when
cold for about 5 minutes and then starts to buck, if I go lightly on
the throttle it smooths out again. Since I don't drive it too far I
have been living with it for several months. You know accelerate
briskly and then back way off on the gas and it is okay. I have
changed the plug wires and plugs (NKG) and still no good. Cleaned the
EGR, throttle body with no luck. Upgraded from new stock wires to
Accell 8MM and bosch platimum plugs. Still no good. I have a code
reader and intermittently it pulls the code (forget the number, think
for crank sensor) for the sensor my SL1 does not have. I tried
reducing the spark plug gap from 40 to 32, still no good. I have a
timing light and one interesting thing is that I get a good signal at
idle but the timing light goes intermitent and even stops flashing for
lenghty periods at higher rpms. (Checked my other vehicle and the
strobe flashes at all engine speeds. Next I put a plug wire on a plug
resting on the engine block and the spark is indeed there at all
speeds. Guess just too week for the stobe pick-up. Last thing I tried
yesterday evening was to open the spark gap to 45 thou. This morning
was the first time my car has not jerked and hesitated on the way to
work in months. It did do some minor bucking on the way home but the
wife says it was okay for her tonight. Crossing my fingers on this one
as I need to get GOVN't emmissions test soon.

 

They have crank sensors just not a cam sensors. I had a similar
situation with a 3.8 and I reached down and could move the sensor
around, it had worked loose and was rubbing on
the...whatchamacallit...steel ring with what is often described as
shutters. Anyhow I would suspect that unless it said "cam". In that case
it would probably be the ignition module or something that has to do
with "compression sense". Btw dont play with your plug gaps especially
if they're platinum and be sure to check the resistance of your spark
plug wires.

 

Check the routing. OBDII saturns are picky about plug wire routing
because they need it to be the right way to sense something weird.

After that, suspect the crank sensor, and if that's not it, ignition
module.

 

I've had the exact same problem with my 96 SL1 for the last 4 years.
(Since I bought it, used)

After replacing plugs, plug wires, O2 sensors etc to try and fix the
problem, I stumbled across this.

http://www.magnecor.com/magnecor1/TechBulletins/TECHSAT.HTM

I did as they recommended (Buy new plugs and gap them at 0.04 instead of
0.06 and VOILA! The problem is long gone.

The silliest thing imaginable, but it works.

 

First I've ever seen this. The TSB 96-T-25 does show up on Alldata.
Thanks for the info.

 

Check the routing. OBDII saturns are picky about plug wire routing

The error he is getting that he says the car doesn't have is likely a cam
sensor error, which relies on the routing of the plug wires. The car doesn't in
fact have a cam sensor per se, but with wires 1 and 4 routed next to each other
near the coil it senses which cylinder is on the compression stroke; that
acting as a cam sensor.