1995 Other Saturn Models Erratic Engine Behavior & Senso

TRAINMEISTER

MEMBER
1995 SATURN
4 CYL
FWD
MANUAL
172,000 MILES

I picked up a dandy 2005 Saturn SC-1 coupe at the towning company auction for $500 with 172000 miles on it's SOHC 1.9L 4-cyl. Engine. It runs pretty darn good but two odd conditions have emerged:

1. The engine won't rev beyond 4000 RPM (not that I rev it up that high much) during acceleration. Engine starts to sputter & jerk. Runs just fine up to 3999 RPM's!

2. Electric cooling fan won't come on unless the air conditioning is running. Turn the A/C off, the car overheats. Funny, should be the other way around!

Since the cooling fan does work with the A/C on, I suspect the coolant temperature sensor may be the culprit.

I suspect the Manifold Absolute Pressure (MAP) or Mass Air Flow (MAF) sensors may have something to do with the latter, but my darn Chilton's manual doesn't give any information about how to check or replace these sensors.

Any advice?

1 Reply

RASMATAZ

MECHANIC
75,992 POSTS

Since the cooling fan does work with the A/C on, I suspect the coolant temperature sensor may be the culprit. You could be right or an engine temperature sender/gauge switch, fan relay problem.

The engine won't rev beyond 4000 RPM (not that I rev it up that high much) during acceleration. Engine starts to sputter & jerk. Runs just fine up to 3999 RPM's!

Won't rev -check the following below
Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires