New Member Working on a 2000 Honda Civic Hx

[Kirt Emery]

Came to ETCG after watching many of his videos on You Tube, which I love. If this is not the correct place to post this question, I apologize. I know I shouldn’t have but I wanted to fix a P401 error code on my son’s car before he went back to college. We pulled the fuel rail to access the egr passages which were blocked. We cleaned everything and put it back together. I felt like the project was a complete success-check engine went off, motor sound better, son felt it started better, etc. On his trip back to college, about 600 miles away, he reported his mpg going from 35 to 25. My first though was- so much for feeling the project was a success.

My first question is to ask if there is something that I could have done to create this problem or is it unrelated. We took off the minimum hoses, left the injectors on the bar and put silicon paste on when reinserting, was extra careful throughout the fix. The care has 280,000 miles on it – when my son brings the car back in a couple of months where would you start to diagnosis the problem? Any help would be gratefully a appreciated.

Topic

[Tri9SS]

First off if the check engine light did not come on I would still say it was a success. I would double check his figures. for example if he did not start with a full tank then fill it to the same level the numbers would be off. The only thing would be a fuel leak but I dismiss that because because there was no mention of that. Once again if the light is off and no faults then just wait till he gets back and double check the MPG. If that is the only thing and the car is driving normal then I feel you can relax and not stress over it. sounds like you done good. Good luck, and take it easy.

[college man]

I take it no codes came back? Idle is normal?
I would check for vacuum leaks on anything that
was removed.

http://www.ericthecarguy.com/faq/finding-and-fixing-the-causes-of-poor-mpg

http://www.ericthecarguy.com/faq/solving-automotive-performance-issues

[Bill]

I know your intentions were good and it sounds like you were very careful with the job you did but you never use anything silicone unless it’s sensor safe on an engine. It can coat the o2 sensor and create problems. If you ever remove fuel injectors again just use engine oil on the “O” rings.

I wouldn’t panic about it unless the check engine light comes on or the car begins to run poorly.

Sometimes available fuel and driving conditions can reduce fuel mileage also and might have nothing to do with the work performed..

[Kirt Emery]

Thanks for the info on silicone. I watched the ETCG video and he used silicone paste when he put the injectors back. I had to order it special and have used it on a number of different applications–actually like the stuff. I will however just use engine oil the next time I pull out injectors. No the check engine light has not come on. My son did check for typical gas leaks etc. today and didn’t find any. Thanks for the reply.

[Kirt Emery]

Correct no codes came back and it idles normal. I took off only the minimum number of hoses to push the fuel injectors out of the way to get to the passages. When I cleaned out the passages, I used a vacuum to suck out the crud plugging the passages. I was thinking some of the crud caused a problem.

Since I’m a weekend hacker, I’m going to ask a dumb question. How do you test for vacuum leaks? As a hacker, you probably guessed that in the past I just start replacing vacuum lines hoping I’ll find the one that is cracked or leaking. Is there a better way? Thanks in advance.

[EricTheCarGuy]

I think that Wystech was thinking that you used RTV silicone on those components. That would be wrong. What you did with the silicone paste was 100% correct.

That said, one thing that could have happened was a vacuum leak. Perhaps the passages were not sealed up correctly and as a result you may have a vacuum leak. To me this seems like the most plausible explanation of the problem you’re having. That or your math was off.

Good luck and keep us posted.

[Dmitry]

I agree with Eric that it’s likely to be a vacuum leak.. Did you use a new gasket on the EGR passage cover? Did you torque it down properly? Spray some starter fluid around the cover and watch for engine RPM increase (fire extinguisher on standby of course). If the RPM increases you do have a leak and will have to replace the gasket/tighten the cover bolts.

On the other hand, I don’t know if it could somehow be related here, but I too once had my HX get about 23 MPG. Adjusted the timing and was back at 36 B)

Good luck!

[Kirt Emery]

Thank you Karma for your comments. I did not use a new gasket, just cleaned everything spotless. Because it was hard to get to I did not torque the bolts down. I will do the vacuum check and timing when the car is back home. My son did report hitting something pretty hard that week also–not sure what it was. Again, thanks for your help.

[Author]

Replies