96 SL-1 stumbles for a few minutes

Hi,
I have a 1996 SL-1 manual with 120,000 miles on it. For about the
first 5 minutes most mornings, it stumbles under medium load. Idles
ok. If revved above 3500, it runs ok. But, when cruising down the road
at 2000-2500 rpm, it will start to buck like crazy. I just downshift
and drive at a higher rpm for a while. After about 5 minutes, it goes
away. I have recently replaced the plugs, plug wires, fuel filter and
engine coolant temp sensor. It rarely throws a code (unless I let it
buck a lot) and if it does, the code tells me I have a cylinder
misfire (not always the same cylinder). It doesn't seem to do it as
much if it the ambient temp is above 80F. I only have a code reader,
not a real scan tool, so I can't check sensors, etc. Any ideas?
Thanks,
Buster

 

Hey Buster -
I think your problem is your fuel pump. A have a 95 that
occasionally acts this way too. (It began acting a lot worse after I
ran it completely out of gas and then had a heck of a time getting it
to run again - I've heard more than once that a fuel pump problem can
be aggravated by running it dry.) Sometimes it seems worse after
making a left turn.

Unfortunately when I tried to borrow a fuel pressure test guage at
AutoZone - it turned out they only had them for sale - not for loaning.
Darn thing was over $80.

Theres another guy that posts on this group and says he had a problem
for over 2 years before he finally got to the real source of the
problem.

Not being completely sure - I'm kindof waiting for mine to give out
completely (if that's what it is).
-WAv

 

Thanks for the tip. I've never run my tank dry, but it is 10 years
old. I'll check it out.
Buster

 

My 97SL2 had problems.....

This the process that seemed to reduce and later elminate the
stalling, rough idling, and spurtering.

1. I cleaned the throttle body.
2. Changed the Coolant Temperature Sensor.
3. Changed plugs and wires.
4. many bottles of Fuel injector cleaners.
5. Later, had the fuel pump replaced(Saturn finally found out it was
defective).

1-4 I did myself, #5 was costly. So far this is the first summer
without stalls, rough starts, and sputtering.

So from what you said, and what I did, it sounds like you should have
your fuel pump checked. You might have a problem with it.

Sorry.

later,

tom @ www.Consolidated-Loans.info

 

Try replacing fuel filter first.

 

New fuel filter 3 weeks ago. Keep in mind, this only occurs for the
first 5-10 minutes in the morning. After that it runs fine.
Buster

 

Would a bad fuel pump only act up for a few minutes in the morning?
Problem doesn't recur until next day. Car has new ECT, plugs, wires
and fuel filter. Will try cleaning the throttle body.
Buster

 

I have a 95SL2 that had somewhat of the same problem at aprox. 90,000mi.
Turned out to be a sticking EGR Valve. When the symptoms got real bad it
finally set a Code 32 (I believe) (EGR System Failure). Replaced the EGR
valve and no other problems. Did it again at aprox. 180,000mi. Same
symptoms, same fix.
Something you might look into.
EGR Valve not cheap ($105) at AutoZone.

Jerry

 

I have a 95SL2 that had somewhat of the same problem at aprox. 90,000mi.
Turned out to be a sticking EGR Valve. When the symptoms got real bad it
finally set a Code 32 (I believe) (EGR System Failure). Replaced the EGR
valve and no other problems. Did it again at aprox. 180,000mi. Same
symptoms, same fix.
Something you might look into.
EGR Valve not cheap ($105) at AutoZone.

Jerry

 

I have a 95SL2 that had somewhat of the same problem at aprox. 90,000mi.
Turned out to be a sticking EGR Valve. When the symptoms got real bad it
finally set a Code 32 (I believe) (EGR System Failure). Replaced the EGR
valve and no other problems. Did it again at aprox. 180,000mi. Same
symptoms, same fix.
Something you might look into.
EGR Valve not cheap ($105) at AutoZone.

Jerry

 

Back to the bad fuel pump issue. If I just drove the car, and then
parked it. My starting habits 'covered' the fact the pump was bad. I
would turn the car on (without cranking), buckle up, and then start
the car. The moment pause in going ON to Cranking gave time for the
fuel pump to refill the system.

Now over night, the system would drain so much, that a moment was too
short, so the engine cranked hard, and ran like crap for the first few
minutes. Since I had my pump replaced the 97SL2 runs very well.

Ofcourse I still get those mysterious "Check Engine" lights. They
solid, never seen flashing, but when I got to an auto zone to have
them checked, the light goes out.

later,

tom @ www.WorkAtHomePlans.com

 

Does it seem to be running lean when cold? The Coolant Temperature Sensor
is supposed to tell the engine computer to provide more fuel till the engine
warms up. If the CTS is defective and registering a "hot" engine even when
cold, then you might have drivability issues. I know you already said you
replaced it, but maybe that one was bad? Saturn CTS is known to fail often,
is cheap and easy to fix.

Bob

 

Any tips on how to tell if it's running lean? I'm pretty sure it runs
rich once it's warmed up, I get a lot of popping back in the exhaust
system when decelerating. Also, when I changed the ECT there was no
difference in performance or gauge operation.
Buster

 

I'm pretty sure it typically fails the "other way" - it goes out with
too high a resistance value. Consistantly, it 'indicates' a low
temperature condition when that is not the case.
It thinks the engine is too cold, and tries to warm it up even when its
hot.
I know that you can increase EGT by leaning out the mixture, but I dont
think that is how it manages to "warm up" the engine. With an over
rich mixture (and higher RPMs especially), I think you might be making
the engine run warmer, even if EGT is not high.

-WaV

 

Tom, I tried your technique and it didn't help. I usually just turn
the car on. Today, I turned it to the RUN position, then took the
trash to the curb. After about a minute, I started the car and it ran
the same.
Buster

 

Sorry to hear that. I was just explaining what happened to me, it
wasn't meant as a fix. You need to get your car to a qualified
mechanic.

tom