1995 b'ville idles very rough and rich, over 2500 rpms runs good. dies if i stop fast, snap-on scanner says "no communication", autozone scanner says "link failure", GM tech2 scanner shows it going in and out of open/close loop. gets pretty good gas mileage. replced plugs and o2 sensor. please help.

If you have an idle air control motor on this vehicle clean it. Use throttle body cleaner and simply spray it until the carbon is removed. Also clean the port that opens into the throttle body. The other thing is to clean the wires on the Mass air flow sensor. Be extremely careful and use an electronics spray cleaner. Allow to dry before reinstalling. This will help with the idle and drivability. You may also be develpoing a computer problem due to the lack of communication betweent he diagnostic port and the computer. Keep tabs on it as it may go out soon.

Thanks, i'll try it. also, after sitting in traffic, after speeding up,it loses power and starts surging, if i put in neutral and turn it off and coast for a few seconds, i start it and it runs fine for a few minutes

didn't work, pulled throttle body, it was really nasty, cleaned everything very well. runs the same, any ideas???

There are only three other items I can think of that may cause this problem, bad EGR valve a Crank position sensor that is going bad or a bad ignition module. I would clean the EGR and replace the ignition module before I went to the trouble of changing the CPS. The former are much easier to change than the CPS. One last thought, since the computer determines the amount of fuel you may have a bad computer that is sending too much fuel to the car due to not reading sensors properly. These cars are hard to diagnose without the codes and since you have a problem with a scanner you may want to consider replacing the ECM with one from a wrecking yard.

cleaned the egr and scanned it with a tech 1 came up with p0172 (too rich) and p1670 (quad driver), now after about 30 minutes of driving, OD quits working, if I shut it off for a few minutes, it works OK.

This web page may give you some ideas on how to correct your problem of being too rich.

http://www.obd-codes.com/trouble_codes/generic/p0172-system-too-rich-bank-1-oxygen-sensor.php

Replaced the computer and it works great, thanks for your help.

THE 1993-1998 Bonneville and it family of GM cars have PCM problems. If you not think seriously, you will waste several hundreds of dollars in replacing sensors, valves, and actuaters. Most rough idling, driving and stalling are caused by the PCM - computer! The crank shaft sensor is also shitty to cause you to loose your hair.

That's why I'm going bald. lol. It drove me and many other people batty trying to figure it out, it spent 2 weeks on 3 different scanners with no results. Fortunately I work in a large body shop and we got a totalled Transport van. I swapped the computer and headlight (Transport headlight are the same as B'villes sometimes) thanks. mike

Michael,I have the same problem...rough idle,surging at 1800 rpm...I have tired nearly everything..(changed egr,crankshaft sensor,wires plugs,rebuilt the tranny,fuel filter,checked fuel pressure)

How hard/easy was it to swap the ECM...? Did you install the eeprom form the old Computer to the 'newer" one...

Could you please outline the procedure...cause thats what I wnat to do next...thanks...

The ECM is easy to swap, 2 phillips head screws under the glove compartment, then unsnap the plastic tabs and slide it out. I didn't swap the PROM, I should have, it doesn't shift right in Perform mode. mike

ever try the throttle position sensor? if the voltage
fluctuates without pressing the throttle. can cause
these hesitation problems.

I tested the TPS...and the voltage was right on....



Since then I changed the ECM..and the coil packs...no diffrence yet..I even checked the timing chain for slack...very little there...


My next thing will be the ICM...if that doesn't do it..then I don't know what will.....

o2 sensors? clean your injectors? fuel regulator?