Aloha from Hawaii all.
Friend has a 97 Monte that stalls at low rpms after 10+ miles of driving.
mechanic told her there was sediment in gas tank that gets stirred up after driving. I call BS. He changed fuel filter but it made no difference.
Here is what I know;
- Car stall at low RPM's or stops (does both only after 10+ miles of driving). Putting in neutral and feathering gas prevents stall. Once car starts stalling it smells like is running very, very rich. Once car sits overnight it runs fine again.
Some sort of sensor is danging a few feet behind the cat. I cant find where it goes to.
My thoughts so far are:
Try can of fuel filter cleaner.
Try to find where sensor by cat is supposed to go or uplug it.

Any other suggestions?
How can I tell if the cat is plugged?
Any input or suggestions appreciated.

Gary Woods
Hawaii
Former owner -85 Monte SS, 86 GN

 

You really can't tell if the cat is plugged to my knowledge - just your performance will suffer. When was the last time a tune up was done? Plugs, wires, etc? The plug that's dangling is most likely your secondary oxygen sensor. If it's unplugged, that may be your issue.

 

it should screw into the exaust pipe, that helps the computer read the air fuel ratio that it it burning. if its dangling and getting strait air that hasnt ran through the cylinder, it is probably telling the computer its not running 14.7:1 and thats its getting more air then gas. this would cause it to spray more gas into your cylinders and run more richer than needed.
if someone installed custom exaust, the screw in part for the sensor may not be there. your options are to go to zzp or some performance shop to get it taken out of the systems pcm. or you can cut out a section of that exaust and install that section of the exaust that has the insert from a junk car. again these are options if there is no threading in the exaust for it to go into.

 

If the post cat sensor is unplugged it won't make the car stall or shouldn't it mostly just a catalyst monitor to say if the cat is working or not. to check if the cat is plugged there are easy tests but should be easy to figure that one out without too much testing...

Is it setting any DTC's? besides a P0420 for the post cat oxy sensor not being attached.

And easy fixes would be clean the MAF (with a specialized cleaner) clean the throttle body with cleaner and clean the idle air control motor.

The sediment thing is definate BS.