ISX 475: Backfire from intake between shifts

Should I just wait until the engine is cool, then unplug it at the connector on the back of the EGR? Your theory could be correct- I've noticed that the boost doesn't feel as robust as it used to. It's like the low RPM boost is gone, and it feels "flat" until the turbo really spools up and gets going. The VGT turbo should provide low RPM boost more than what it feels like now.

 

Will do. I load out tomorrow, and should have some feedback on Wednesday how it went.

 

Which plug on the EGR? The one that plugs into the back of it, or the one that has about a 3" lead wire with the harness on the end? Or both?

 

Ok, I have them both unplugged, so I wanted to be sure that was going to work for the test. So far it hasn't coughed, but I'm empty. Most of the coughing happens when I am loaded and pulling a grade, then down shift. I'll run it like this for a few days to see how it does.

 

UPDATE: With both unplugged it made no difference. So I waited until the next morning when I was sure the engine was cold, turned the key to the run position, but not start, to make sure the valve closed. Then I unplugged the wires from the back of the valve only. This worked! Yes it throws a code for PID 146 OpenCirc, but otherwise NO MORE COUGHING!! Also gained over a point on my MPG and the truck runs a lot better. It pulls better, sounds better, no more black clouds from the stacks after shifting, and it doesn't feel "flat" anymore. Like the boost is back to where it should be.

One problem... With the EGR valve unplugged, when I pull a long steep grade, I get a red engine shut down light and a code for "Engine Oil Temp High". The fan is coming on when it should, and keeping the coolant temp below critical, yet still the oil temp is high. Before I rebuilt it, I had the EGR unplugged and it did this same thing. It only happens when the EGR is unplugged though. Is there some relationship with the EGR valve and the engine oil temp?

I was planning on just making a steel plate to go between the valve and the engine to block the exhaust gas, and plugging the valve back in to get rid of the light. Feasible?

Thanks for your help, man. A lot of people have benefited from your participation here, me included!

 

Follow-up on this issue: Here's a tip from another owner who had the same issues with his ISX "sneezing" back into the intake, and how he finally resolved it by having the shop clean out a couple of small tubes on the air intake. If anyone knows what he's talking about specifically, can you please elaborate a little? I still have this same issue, and have been unable to fix it so far, on my '05 CM870 ISX. His quote and the source link follows:

Source: http://www.topix.com/forum/com/###/TR5K0N8EAKMOMO28S/p2#c23