1991 SL2 Low RPM Rough and Stall problem

I have a 1991 SL2 that idles very rough when at low rpm, even to the point
of stalling. The rpm will fluctuate between 500 and 1500. When I put it
into neutral it does not do this. I have gotten a 26 diagnostic code and
replaced the PCM and the throttle position sensor, to no avail.

I would appreciate and ideas on what this may be.

 

You do not offer much additional information here beyond the symptoms to go
on: What is the mileage of the vehicle? What is the condition of the
plugs, wires, ignition tower cap? When was the throttle body and AIS last
thoroughly cleaned with a good TB cleaner? Was the EGR ever replaced and if
so at what mileage and age? Is the Coolant Temperature Sender (CTS)
original equipment? have you looked to make sure all vacuum hoses are
connected and none are cracked/leaking? These are all things that can
impact engine idle

Bob

 

What is the mileage of the vehicle? 136,500 I have only had it about 2,000
miles

What is the condition of the plugs, wires, ignition tower cap? Appear to be
good

When was the throttle body and AIS last thoroughly cleaned with a good TB
cleaner? Unknown, but I am get cleaner fluid.

Was the EGR ever replaced and if so at what mileage and age? Unknow, but I
have ordered a new through NAPA.

Is the Coolant Temperature Sender (CTS) original equipment? Unknown but I
got a new one today.

have you looked to make sure all vacuum hoses are connected and none are
cracked/leaking? All appear to be good.

I replaced the alternator, which did not work at all, as well as the fuel
filter, PCM and throttle position switch.

These are all things that can impact engine idle

Thank you for the suggestions.

Rob