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My recent work was clean the EGR pipe and the inlet hole where EGR pipe connects to the intake(using screwdriver and toothbrush), about two weeks ago. Check Engine Light went away and never come back.
I have small hand, so I only removed the bar across the engine(which is holding AC low pressure line) and got the work done. I may have used a bit too much carb cleaner. When I first started up engine after putting EGR pipe back on, engine ran very rough. I raise up RPM a little. After a while, it ran very smooth and normally. I did dis-connect battery to clean the code. But I didn’t if disconnecting battery resets ECU or not.HOWEVER, when the first time I went to gas station to top off gas tank after cleaning EGR, I calculate MPG that is about 12.5, even worse than before 14.5. It might because these day are getting little bit cooler, around 70F. But It should not get worse MPG.
About a week later, I disconnect battery and remove 3 ECU fuse in an attempt to reset computer completely. I haven’t gone to gas station yet. But roughly estimation based on fuel gauge tell me I used about 1/4 18Gal Tank in about 50 miles.
I tested with OBD tool. I attache fuel trim log below. It was about 10 min driving in town (about 30~35mph speed limit)
Eric said NEVER assume. So I think I should not assume O2 sensors are absolute correct and give correct fuel trim reading.
Why I am getting worse MPG after cleaning EGR passage.
BTW, I am runing 91 premium gas without ethanol.
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jenaflex
see if you can get fuel trim numbers (both short and long) for varying rpms.
like idle,1000,1500 and 2000
fuel trims are conducted inside of “cells” so fuel trim numbers for idle can be diffrent for higher rpms as the computer moves up through the “cells”.
Intake leaks will often show up better in the idle “cells” and fuel volume /pressure issues will show up better in the high rpm/load cells.
I will try to record reading tomorrow.
BTW, If I pull 3 ECU fuse out and disconnect battery, did I clear the KAM memory in ECU?
You will need to remove the battery cables for at least 20 min or remove and touch both battery cables together to discharge the capacitors inside the pcm.
As to your question about MPG after your EGR cleaning, you stated that you removed the tube from the rear of the intake manifold. I’m not sure if you removed the plate as well but I do for the best cleaning. That said, this IS the intake manifold. If the gasket is not sealing properly you will have an intake vacuum leak which can equate to poor MPG. If you have poor MPG after you did something, it’s likely the something you did that caused the problem. Never rule yourself out as the cause of a problem.
Keep us posted.
Hey, Thank you Eric. You have been my online mentor of fixing car for a while. I learned a lot.
In terms of your point, I didn’t remove intake. All I did was remove EGR passage and its metal plate gaskets at two end. I cleaned them and the holes on both intake side and exhaust side.
Will EGR gaskets leak cause vacuum leak?
It is possible that the old EGR metal gasket didn’t sit on EGR passage flange really well.
I tried your carb cleaner method on the exhaust side of EGR passage gasket, which is easy to access. It didn’t change idle. I may spray some on the other side this weekend.
BTW, I had my fire extinguisher next to me, lol.
I didn’t mean to imply that you removed the intake, just the tube and plate. I’m very familiar with that set up. As I stated, that IS the back of the intake. Any leaks in that area are vacuum leaks and can cause fuel economy issues.
Didn’t feel the need to start a new thread. I have a 94 Acura Legend L AT, which basically has the same EGR setup. If I were to be thorough in cleaning out the build up and remove the pipe and plate, I assume I should replace all the gaskets I encounter? Specifically 2, 7, 9 (x2), and 10 in this diagram?
Just double-check, there are metal plate and gasket, two separate pieces? I ordered “ACURA OEM 18721-PR7-A01 Exhaust Air Supply Gasket“. What I got is a piece, that looks like grey-ish special fiber gasket, NOT a metal piece.
My original EGR gasket looks like a metal piece.
I am a little bit confused. Should I just install new fiber-like gasket without my original metal piece?
The ‘metal piece’ is what’s left of the gasket. When it was new it looked like the gasket you have. At least that’s what I suspect. If you only removed the pipe and not the plate beneath it, that may be all you need to deal with. However, if you removed the plate below the pipe then you will also need that gasket. That said, you also need to make sure you clean all the old gasket material off before you install your new gaskets.
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