Hey all I have been dealing with a rough idle issue for quite some time
I have replaced all Fuel components, Fuel pump, spider, internal fuel lines, filter and have replaced pretty much every sensor and connector on the vehicle except for the Map sensor and ignition control module Would either of the 2 in your opinion affect the idle problem?? also i have replaced the Idle air control unit but it's interesting that if i reset it using my Tech 2 scanner it seems to run better for a short period of time any thoughts?

Thanks

 

Have you cleaned/checked the EGR valve? How about the tune-up items (plugs,wires,cap & rotor)? There is the possibility that the PCM has gone bad.

 

I have done a full tune up and cleaned the EGR and replaced with the screened gasket
The PCM is a possibility The truck has a total of 316,000 miles on it I replaced the original engine at 200,000 miles I am going to try another tune up with ac delco wires,cap and Rotor instead of the Napa brand if the pcm went bad wouldn't there be more issues than just a rough idle?

 

Have you cleaned the throttle body, paying attention to the IAC valve? Have you ruled out a vacuum leak?

 

Hi,
Took the plenum off the other day when replacing the internal fuel lines and scrubbed down the entire plenum and all Sensor ports. I conducted a vacuum test off the back of the plenum to the brake booster and the smaller line off the passanger side all held steady pressure,in the green. I have a few used EGR valves that I swapped around but no change Wondering if I should spend the money on a brand new one, and another tuneup using AC Delco cap, rotor, wires. Other than that the only original part is the Ignition control Module and MAP sensor
Any Thoughts?

 

One other thing I could use an opinion on in reference to this Idle issue
when the truck is running good the voltmeter gauge shows 14volts when it is rough idling the gauge shows just below 14 volts. while in the rough idle mode I put a volt meter on the battery and Alternator both show between 13 and 14 volts.
Starting from the battery i checked each wire running off it and cleaned each connection, I also notice if i put on the brakes and Signal light,the instument cluster Volt meter Shows a drop. Any ideas or maybe just a bad volt gauge? also seems to act up more on Humid days. Grasping at straws here, any thoughts

 

Alternator output is proportional to engine speed. When it is running rough, it is quite possible that the RPMs are dropping to the point where it is not maintaining the output high enough to keep the system at 14V.

Acting up more on humid days points straight at the ignition system (wires, cap/rotor, distributor, coil, ICM, etc).

 

Ok thanks I will Focus on the ignition system, The coil has been replaced, I will try another Tune up using AC Delco parts and if there is no change I'll try the ICM
and post my results.
Thanks again

 

The coil and ICM can be tested by most chain autoparts stores. Just have them do it repeatedly to heat the components up. Most problems occur with increased heat.

 

Did a little reading up on Lazy O2 sensors and remembered while observing their performance on my scanner Notice one hanging up a little but then seem to operate ok.
so today I switched the sensors front to back and guess what i got a DTC for O2 sensor
low voltage don't remember the DTC # so i cleared the code and will monitor it for the next few days. I think a Lazy O2 sensor might be my problem and have notice gas milage is getting worse, Will update soon