I have a 03 duramax that has a surging idle. The truck will idle at 700rpm then go up to about 800rpm, and slowly return to 700 rpm, repeating this cycle about every 15 seconds. The truck also has a k&n air filter and intake system on it. I have a reaccuring code of p0101, that I thought was from the oil on the k&n filter but I recently cleaned the filter without oiling it again and I got the same code. But this time when I checked the codes I also had a p0402 code( this is the first time I have gotten any code other than the p0101 ). Does anyone have any suggestion on what could be causing this surging idle issue? Thanks for any help.

Try cleaning your MAF sensor with cleaner from one of the auto parts stores of your choice. Be careful as the sensor is very sensitive. Oil from your K&N setup will coat the sensor and render it useless to do its job. Amsoil makes a replacement filter element that does not take oil and is better at filtering.

As for the 100RPM surge, you likely have a FPR (Fuel Pressure Regulator)going south on your truck. Has it been getting worse as time goes on? Most times it surges when the truck is cold and goes away as the engine warms up. If it now does it when the engine is warm you need to install a new one. They are not hard to replace, just a bear to get to.

Your P0402 is a EGR code, clean you MAF sensor and see if it comes back with the MAF getting the air that it needs. Never know, the surging could be MAF sensor related also!

Hope this helps,
Tony

I have cleaned the maf senser with no help and the code still came back. I did some research last night and I have all the same symptoms that are common in this thread except for the surging idle, maybee the two issues are not related. http://www.dieselplace.com/forum/showthread.php?t=152751 Where is the fuel pressure regulator located at?

I think I had this problem, check out my earlier thread:
http://www.dieselplace.com/forum/showthread.php?t=156997

page 2, post #16,
Only did it at Idle, about 100 rpm up then back down, repeat.

I ran B20 Biodiesel through it and I havn't had it since, that was right at 1 year ago.
Good luck