I recently had the head of my 186k miles '99 Accord, 2.3L 4-cyl. reworked due to a burnt valve. I cleaned everything up and put it back together with new EGR valve, Cat, plugs, O2 sensors, belts, water pump .... It starts & runs fine except that the OBDII now detects a P1491 - Insufficient EGR lift ( I have a scanner). Driving the car, I notice some surging at around 2k rpm.

I removed the EGR valve and put it on the bench. I measured the resistance across the internal potentiometer and the total resistance is 4.6K ohms; there is resistance measured at the signal pin to each end of the internal resistor. Not knowing what the specific values should be, it does read the way one (I) would expect a potentiometer.

I then applied 12V across pins 4 & 6, per the Haynes manual, and the valve does open. Now for the confusing part ... with the valve open, the resistance measured from the signal pin to either end of the internal resistor is extremely high - multiple megohms - seemingly impossible for a potentiometer with a total resistance of 4.6K ohms. If I press or pull on the open pintle, the resistance does vary, but not predictably. The only pintle position where the resistance seems stable and appropriate is when the valve is closed.

Have any of you performed similar bench tests? Is what I'm reading normal, or do I have a bad EGR valve? Or, is my test bogus?

Thanks in advance.

 

most people just clean there EGR valve out and everything is fine I would suggest doing that before buying a new one especially since it has passed the bench test

 

Thanks for the reply - This is a new EGR valve with only a few hours of running time on it. I did clean it, just to be sure, but it wasn't really that dirty.

What I'm trying to understand is what's normal for the resistance checks made with the bench test? I'm hoping there is someone out there who has done similar tests and can tell me what the readings should be.

I've Googled my brains out & have found nothing.

thanks again,

 

Just an update for those interested ... it appears that energizing the EGR solenoid with 12 volts on the bench is not representative of the voltage applied by the PCM. I don't know what that voltage is (yet), but when I applied less voltage on the bench, the valve opened less and the resistance at the valve lift signal pin was within range of the internal potentiometer. I now suspect that the EGR is probably operating OK & my initial test was in error.

I'm nearing the end of my rope with this issue & may have to swallow my pride and take it to a shop - probably Honda. It wouldn't surprise me to find that the after-market EGR valve is still the culprit, giving a valve lift signal that's not the same as what a Honda part would give.

 

have you tried cleaning and using the old valve? What company made the new valve? Don't take it to Honda man, all they will do is replace the valve with an OEM one and charge you an arm and a leg.

Also, have you tried cleaning the EGR ports?

 

Thanks for the reply! -

Unfortunately, the original EGR valve got tossed. The new one is from a nearby foreign auto parts place which does a lot of business with garages.

Yes, the ports are clean, mostly as a result of having had the head reworked. The EGR port on this head is different from everything I've read regarding port cleaning. There is a single hole which goes from the #4 exhaust valve port to the base of the EGR. That path is clean. I've looked closely and do not see any other path to the EGR from the head. I cleaned the path from the EGR to the intake when I had that off and apart. All EGR paths should be unobstructed.

I know there are any number of possible causes for the PCM to decide that there is insufficient EGR lift. I'm leaning toward believing that the after-market EGR valve may not be giving the same lift signal as the Honda part would. It goes against my grain to just go out and buy another part before I'm sure, especially given the price. The MAP sensor appears to be working, according to my scanner's real-time readout, but even so, the MAP sensor's output could be varying but wrong. And then there's the PCM, itself ... I don't even want to think about that ....