Engine Performance problem
2001 Chevy Express V8 Two Wheel Drive Automatic 330000 miles
My van all of a sudden started stumbling and showing a loss of power (only at mid-upper rpms). Check engine light came on, so I took it to autozone and they gave me p0401. I have researched this and researched this, changed out the egr valve. I have read about vacuum lines being clogged-I believe mine does not run on vacuum. I read about carbon build-up--I saw some, but only around outside edges, didn't seem bad to me. I am guessing that it might be the sensor for the egr valve, but don't wanna play change this, change that. I have a fluke voltmeter, if it can be used to check the sensor, but don't know how to check it. This van has 330k on it, and I want it to see 1000k because I am a poor floorman that cannot afford a new van; so I do my very best at fixing/maintaining it. I have some training from UTI also, but like I said I am a floorman now. Your input is greatly appreciated.
The code is for insufficient air flow. Even though it wasn't plugged, are you sure the valve is working properly?
October, 18, 2010 AT 1:50 PM
I am " pretty sure" that the Egr valve is working because I bought and installed a new one with the same results.
October, 18, 2010 AT 1:51 PM
That code is insufficient EGR flow but I doubt it has anything to do with your symptoms. This EGR system is self contained within the EGR valve so there are no other components. The most likely problem is the passage between the EGR valve and the throttle body is plugged up with carbon. You should be able to clean it with some carb cleaner and a coathanger.
As I said though, it's doubtful that will make it run any better.
October, 18, 2010 AT 2:04 PM
So what you are implying is that I need to disregard the problem code and use the basic engine troubleshooting techniques to identify my problem? Ie: checking for proper spark, compression, fuel flow etc?
October, 18, 2010 AT 2:14 PM
No, not exactly. You still need to resolve that code but you will likely have other issues to resolve after that.
A scan tool would be helpful to analyze all the sensor data during the failure.
October, 18, 2010 AT 2:17 PM
I am going to try and return the new egr that wasn't the problem and trade it for a scanner. Hopefully this won't kill me, but make me stronger.
October, 18, 2010 AT 6:23 PM
Ok, so I got a scanner. First I cleared the prior code, which never came back. I recorded live data during idle, cruising at 55, acceleration, and deceleration. I am clueless at this point. I could not record the full acceleration at 3/4 throttle because it started pinging severely, which worried me, so I let off of it. I did get a 1/2 throttle acceleration though.
October, 18, 2010 AT 6:26 PM
That's the EGR problem causing the pinging. Fix that first.
October, 18, 2010 AT 6:30 PM
So then, since the new egr valve did not correct that problem, what am to do? And thank you for all of your advice so far.