I have a 92 Saturn SL2 which surges when driving. If under load it doesn't surge but when just going city speed it just bumps and jerks. Any idea what might be the cause? What Kind of gas milage should I be getting? I get roughly 38 mpg. Is that good?





Any suggestions would be appreciated.


thanks

 

How many miles?



Manual or Automatic?

 

The saturn has 20700 Km's With a standard transmition. It runs fine when it is under load, or during highway driving. When you do city driving it just seems to jerk.

 

(I'll assume you meant 207,000 km (about 129K mi) based on the age of the car).



First thought would be clutch wear issue -- but this should get worse
under load -- and show signs of slipping (rpms rise but car doesn't go
any faster). Plus, I wouldn't expect you to get 38mpg on a dying
clutch plate.......but it may actually be that the clutch is slipping
under load too --- any burning/hot clutch smell under load?



Do the rpms gyrate wildly (up and down) on their own when the car is
jerking or is it that once it is in gear, the car jerks whenever you
give it gas (presumably at the lower rpms)?



Not trying to answer your question with more questions, but this one may indeed not be staightforward to track down.....

 

No I don't think the clutch is an issue. There is no burning or hot smell at all, nor does the rpm increase or decrease. Any chance of it being the egr valve? Or fuel filter. I've changed the ignition wires, the spark plugs, and the ignition coil, So I know it's not that. Any idea if there's any other sensors I should be looking at?

 

Service Engine Soon (SES) light on? If so, any codes?



Does the car start easily? Does the car idle smoothly when warmed up? Does it start easily when warmed up?



Try the following in the order listed -- they are all common S car issues.



0) Replace Engine Coolant temp sensor and connector (Cheap)



Replace the engine coolant temperature sensor. Originals designed
poorly and have close to 100% failure rate from what Saturn techs
say. (Many things are affected by this temp reading).



Get the brass replacement CTS from Saturn parts dept. Also replace the connector at the end of the wiring harness.



[There is also a separate temp sensor for the gauge on the dash -- don't wory about that one.]



1) Clean the throttle body



Remove the air intake at the throttle body. Rest a shop rag under
the throttle body opening. Use spray cleaner for throttle bodies
(do NOT use carb/choke cleaner -- it will ruin the internal
surfaces). With the engine off, hold the throttle wide open
(under the hood) and spray some cleaner in there -- be sure to get both
sides of the throttle plate. Use a soft toothbrush to remove the
crud from the back side of the plate.



Do not use more than a 1/4 of the can (at the beginning)-- the stuff is
pretty flammable and you don't want it to go off like a bomb when you
start the car up.



Remove the shop rag.



Start the engine -- it will be harder to start -- work the gas as necessary to start it up.



Once idling smoothly, hold the rpms at about 3500 rpm for 20-30sec at a time to flush the cleaner through the system.



Then go under the hood, and work the throttle by hand while spraying
the the cleaner into the throttle body -- you'll have to work the
throttle to keep it from stalling while doing so. Kick the rpms
up around 3500 again while doing this.



Throttle should be much freer and revving should be smooth between idle
and 4000 rpm in neutral-- do it slowly to make sure there is no rpm
range where it stutters or hesitates, and quickly to confirm that the
car's computer responds somewhat properly to real-time requests for
changes in air/fuel mix (no stalling/sputtering).



If the accel and decel are not smooth, then , MAYBE.....



2) EGR valve not operating correctly ? (you're probably due for a flush/replacement anyway (not cheap)



I suppose your EGR could be stuck open or not closing properly, but

EGR issues usually are worst when engine is under load or changing load
(accel and/or decel). Check the EGR solenoid when the engine is
hot to be sure it is actuating the EGR valve properly.



3) Camshaft position sensor (guessing)



Never replaced one, but it's worth a try if any of the stuff described below seems to apply in your situation.



I've experienced wierd jerky accelerations when the car's computer
thought that the CPS was malfunctioning (car was running on 3 cyls--
the readings were out of acceptable range, but the sensor was
fine...). The computer actually changed the timing (for the
worse) resulting in the jerking effect described above.
Strangely, the problem was only when stepping on the gas -- once it got
to a steady speed thre was no more jerking. (For the record, a 3
cyl saturn will run (roughly) without jerking if the misfire code for
the dead cylinder sets in the computer before the camshaft malfunction
code can set....)



Also, others here have reported stange behavior of this sensor when the engine is warm (no-start, hard to start).

__



I'm not a fan of "massive sensor swapping"-- don't swap out stuff
unless it actually makes sense -- otherwise you find yourself changing
multiple things at the same time and you lose your ability to
troubleshoot because you can't tell which change did what, if
anything......



Keep us posted.....



Derf