Questions and Answers

Stumbling Saturn SL2 Q. Hi Mr. Ciulla, my name is Ricardo from Detroit and I have a little mystery here. Please help me. 1992 Saturn SL2 DOHV 112,000 miles 1G8ZK5475NZ257657 This only happens when I am driving slowly, five to ten mph when the car is at normal operating temperature (after five to ten minutes of driving).

When I press the accelerator the car stumbles if I release the gas pedal (if I keep accelerating everything is fines, the car runs fine), it does it even if acceleration and deceleration is not sudden, when this happens you can see rpm and oil pressure gauges go down simultaneously (some times rpm go down to 200 or 100 and recuperates and other times it dose not recuperate and cuts off and while cutting off some times sputters.

When I am coming back from the freeway, 60 to 70 mph, it decelerates nice and smooth, you can see rpm decreasing nice as long as you don't touch the gas pedal, when you do it, at around 10 mph it does it again. We changed the PCV valve.

• IAC Valve (after market).
• Cleaned Throttle body.
• Spark plugs.
• Coil pack (both).
• Did not change wires, but look kind of new.
• Inspected Oxygen sensor and looks kind of new.
• Inspected EGR Valve and diaphragm seems to hold vacuum.
• Spindle on EGR Valve seems to move freely up and down while you acceleration and deceleration.
• Inspected TP Sensor, looks fine.

Ran the unplug it test on:

• Oxygen sensor.
• TP Sensor.
• Map Sensor.

And guess what? Keeps doing the same thing. Any suggestions would be greatly appreciated.

Thanks for your valuable time.

A. TPS looks fine???? Everything can look fine but is it working properly? That is the question. You need to put a scanner on it and duplicate the condition while watching the data for any sudden changes. A open in the TPS would do this. A overactive EGR would do this. You could unplug the EGR to see if it stops.