My Accord 99 V6 was throwing P1491 "Insufficient EGR lift detected" for quite a while now. It did it once last winter, I reset the code, and it didn't come back until this January, and since January it's very persistent: comes back three trips after each reset, so I decided to do smth about it.

I'm aware of the TSB suggesting that EGR passages should be cleaned in the intake manifold whenever P0401 (Insufficient EGR flow) or P1491 is raised. I'm kind of puzzled why TSB mentions P1491. It seems to be purely EGR valve related. Really, how can the blockage of EGR passages affect the degree to which the valve opens?

Nevertheless, I decided to try approaching the dealer with the TSB and asking them to perhaps do the cleaning for free despite me having 93K on the odometer (and extended warranty ending at 80K). Well, that didn't work out very well. They said that they need to call Honda, and for that they need to read the codes (even though I already gave P1491 to them), and that will be $80, and even after doing it, according to him, chances of getting approval from Honda are slim. Errrr. That's after me doing all service there and paying them to change my timing belt month ago.

After the failure at the dealership I decided to actually take a look at the EGR valve. Unscrewing it didn't reveal any gunk or excess of carbon deposits: everything was pretty clean. Maybe I'll post some pictures later, but it was really clean. I also verified that the valve actually opens when 12V is applied to pins 4 and 6. Then I followed the troubleshooting chart from Alldata, measured resistance between pins 1, 2 and 1, 3 and verified that there are no shorts or infinity between them. Applied voltate to 4 and 6 while the engine was idling, and it almost died, which is a good sign according to the flowchart (it confirms that the valve actually opens and that the EGR flow is there).

So, according to Alldata, my valve works just fine, and the only thing left to blame is the ECU, which I'm just afraid to blame given how much it will cost me to replace it

I could try cleaning the EGR passages in the manifold myself, but given the pristine state of the EGR valve and that the engine actually reacts to me opening the valve at idle, I think it will be a wasted effort.

I think there's got to be more troubleshooting I could do before actually taking the manifold apart. Alldata's flowchart mainly targeted the valve and the state of wires going from the valve to the ECU. It didn't suggest any vacuum tests, for example. Is there anything else I can look at? Haynes avoids this topic, I hear that Helm may have more troubleshooting charts. If anyone has an electronic version of Helm, could you please, please copy/paste the chart?

Thanks!

 

Good post.

Alldata is the same as Helms FYI. Chilton's won't provide any extra help.

I think the fact you're overlooking is that you're spending hours and hours on this to save yourself an hour of easy labor. The intake manifold is a very quick job and just because your EGR valve entry ports were clean does not necessarily mean that the EGR ports in the cylinder head and manifold are clean. Taking off your intake manifold and cleaning it up should be routine mainttenance anyway for the paranoid car enthusiast.

'Insufficient EGR Valve Lift' indicated that the EGR valve isn't able to lift to the fully open position, either due to air blockage, mechanical or electrical failure. If you clean out the EGR ports you can completely eliminate the possibility that it isn't receiving enough exhaust gasses. It seems as if you've already ruled out the electrical possibility. That leaves either mechanical or a bad ECU. Your dealer will probably charge you a pretty penny to swap in a known good ECU and troubleshoot it, and EGR valves are pretty expensive. As any mechanic would say, do the cheapest fix first and work your way back from there. Clean the EGR ports in the head and manifold, then see if the problem persists.

 

That's the thing. The valve snaps open easily. No hesitation, no stickiness, no deposits that would prevent it from opening completely. Btw, did anyone try unscrewing the thin bolts in the valve and actually taking the valve apart?

True... I guess I'll go and order new gaskets then...

 

All I did was spray carb cleaner into the ports in the bottom of it, i didn't want to take the chance of damaging the valve mechanism.

All you need are two TB gaskets, don't order a new intake manifold gasket. Also, you should have replaced the EGR gasket if you didn't do that.

 

Why do I need two TB gaskets? Are they installed together as one?

About taking off the manifold... The TSB doesn't say anything about dropping fuel pressure or dealing with fuel rails. Yet I saw some posts here recommending to even buy injector o-rings in advance. So, what's the real deal here? Do just like the TSB says (detach TB, then all cables and hoses from the manifold, unscrew and clean manifold and put everything back together), or are there catches and gotchas like fuel pressure release?

 

There are two different TB gaskets, one TB side and one IM side. Your dealer will know.

The intake manifold and fuel rails are completely seperate. The only o-rings you might want to buy are the spark plug o-rings if you take off the valve covers and want to check their condition. I did and all of mine were in good shape. There are exactly zero surprises in this job. Take the TB off, pull it back far enough so you can get the IM off, clean, then replace. The only tricky part is pulling the TB around because it's attached to the throttle and cruise cables.