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Discussion Starter #1 (Edited)
EGR valve replacement is expensive - around $200 whether it is OEM or aftermarket. There were several threads on cheaper replacements, which ended sort of inconclusive. I want to share what I learned about about Insight EGR valve - how it works, electric specs, what can go wrong, cleaning, testing, and replacement options.

The valve is not flip-flop, on-or-off type: it is continuous. The extent of opening is controlled by voltage applied to valve's solenoid: the higher the voltage, the more valve opening. Correct valve opening is monitored by a potentiometric position sensor. For the valve to function correctly, the pintle must move freely throughout its whole travel, it should be tight in its seat when the valve is closed, and potentiometric sensor should have correct resistances.

Looking into it, the EGR valve connector has 3 top (1,2,3) and two bottom (4,6) blades. The top three blades are for the position sensor, and the bottom two are for the solenoid. Potentiometer wiper is 1, and solenoid (-) is 6. Normal potentiometer resistance (measured between 2 and 3) is 4.5 - 5.5K. The solenoid is about 6.5 ohms.

The most common problem is carbon buildup. Carbon deposits may obstruct the passage, but, more importantly, they interfere with pintle movement and may cause incomplete closure. Much less common are open solenoid circuit (no continuity between 4 and 6), worn potentiometer (increased resistance or no continuity between 2 and 3, intermittent wiper continuity), or out of spec sensor voltage, the latter being an ECU defect. All these defects will throw EGR trouble codes.

All the electrical troubles necessitate valve replacement. Luckily, carbon buildup does not: it is easy to clean. Ultrasound bath is the best way to remove carbon, however carb spray and a piece of soft steel wire will do good job too. Cleaning must be done before the tests.

For the tests, it would be handy to have a pigtail connector cut off junk Honda wiring harness. First, check resistances of solenoid (4,6) and potentiometer (2,3). If these are correct, check wiper connection: resistance between 1 and 2 should be 1.3 - 2.2K when valve is closed, and 3.5 - 4.9K when it is fully open. Next, connect solenoid to regulated power supply. Gradually increase and then decrease voltage from 0 to 12V. The valve should smoothly open and close as you do it. If it doesn't, spray more carb cleaner inside the valve and work the valve by connecting and disconnecting 12V to the solenoid. After assuring unrestricted pintle movement, it might be advantageous to lightly spray valve's inside with dry moly lube for pintle lubrication.

To test valve tightness, turn the base up and pour a little bit of carb spray into the pintle valve. If the liquid doesn't flow through, the valve is tight. If the valve is not tight, this can be fixed by rotating the pintle with Allen wrench while applying some pressure. This will grind off carbon deposits on the sealing surfaces.

As to replacements, I compared my Insight valve to 3 other valves from different Honda cars (2.4 and 3.0L Accords), which can be bought used for as little as $10-20. All the valves have same connector pinout, base pattern, pintle diameter and travel, and solenoid resistance. Potentiometer resistances were within 20% of each other. To be more precise, the valve from my car and the valve marked EE01 had 4.6K pots, whereas the two AC01 valves had 5.4K pots, which I believe is not important. The differences were in the orientation of the connector:

DSC_0204_zpsmpacvjh8.jpg Photo by sser2 | Photobucket

This orientation is also not really important: the Insight harness will accomodate all these valves. The valve on the left is the one from my Insight, it appears to be an aftermarket replacement. OEM valves from the Accords are all Siemens made in Mexico.

There is a difference between bases of aftermarket and OEM valves:

DSC_0205_zpstk9fljpm.jpg Photo by sser2 | Photobucket

Aftermarket is left and OEM is right. Aftermarket has larger input opening, which is insignificant. OEM's base can be separated from solenoid housing using a T-type wrench, whereas the aftermarket valve cannot be taken apart. Also, the OEM pintle can be turned using Allen wrench, whereas the aftermarket pintle doesn't have such an option.
 

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Great info, thank you for your research!

In summation, which part number for an Accord would you recommend for the closest replacement?
 

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The most common problem is carbon buildup. Carbon deposits may obstruct the passage, but, more importantly, they interfere with pintle movement and may cause incomplete closure. Much less common are open solenoid circuit (no continuity between 4 and 6), worn potentiometer (increased resistance or no continuity between 2 and 3, intermittent wiper continuity), or out of spec sensor voltage, the latter being an ECU defect. All these defects will throw EGR trouble codes.
Good writeup but I'm not sure about the ratio of common to uncommon.

The Herky Jerky, stuttering on lean burn transition etc in my experience with my own and numerous customers cars are all down to the worn/bad potentiometer issue and generally nothing to do with carbon buildup.

I would say the carbon build up issue is less common than you think, and the bad pot is much more common. The pot also suffered a manufacturing defect in some units where the wiper was installed reversed and gouged a furrow in the pot carbon track.

The pot can sometimes be fixed by moving the wiper to a fresh part of the track or reversing it if it's installed the wrong way round. People inc myself have even tried adding external pots as replacements!!
 

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My findings mirror this also.



Good writeup but I'm not sure about the ratio of common to uncommon.

The Herky Jerky, stuttering on lean burn transition etc in my experience with my own and numerous customers cars are all down to the worn/bad potentiometer issue and generally nothing to do with carbon buildup.

I would say the carbon build up issue is less common than you think, and the bad pot is much more common. The pot also suffered a manufacturing defect in some units where the wiper was installed reversed and gouged a furrow in the pot carbon track.

The pot can sometimes be fixed by moving the wiper to a fresh part of the track or reversing it if it's installed the wrong way round. People inc myself have even tried adding external pots as replacements!!
 

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I installed an Accord V6 EGR valve on my current Insight right after I bought it, and 12K miles later it runs really smooth with no ill effects, and I average over 70 mpg on every tank. It went on fine, and came with the OEM style gasket.

Standard T Series EGV658T EGR Valve | eBay
 

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Discussion Starter #7
Great info, thank you for your research!

In summation, which part number for an Accord would you recommend for the closest replacement?
Honda part numbers beginning with 18011 or 18710, with a few exceptions. However, when buying used or from a junkyard, there will be no Honda part numbers there. The donor cars to look for are 98-07 Accord with a 4 cyl or 6 cyl engines, some Acuras and Civics, Odyssey, Pilot. You definitely should look at the pictures and positively ascertain that general appearance, connector, and base are as in my pictures. Also, make sure that connector is pointing from 3 o'clock to 7 o'clock, as in the picture. Buy cheap, test, and if it is not as described above, return it.
 

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Discussion Starter #8
Good writeup but I'm not sure about the ratio of common to uncommon.

The Herky Jerky, stuttering on lean burn transition etc in my experience with my own and numerous customers cars are all down to the worn/bad potentiometer issue and generally nothing to do with carbon buildup.

I would say the carbon build up issue is less common than you think, and the bad pot is much more common. The pot also suffered a manufacturing defect in some units where the wiper was installed reversed and gouged a furrow in the pot carbon track.

The pot can sometimes be fixed by moving the wiper to a fresh part of the track or reversing it if it's installed the wrong way round. People inc myself have even tried adding external pots as replacements!!
"Stueveo My findings mirror this also."

Guys - I stand corrected. Thanks for pointing to the importance of the potentiometer problems. On our side of the pond, there is no need to fix pots since our junkyards are full of cars with suitable replacement valve.
 
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