I have two 2001 Accord Ex one auto (gold) and one manual (silver)
One day the gold one randomly died at the light and wouldn't stay running without my foot on the gas.
I cleaned the air filter, throttle plate, no engine light codes were appearing
I ordered a new IACV hoping it was the issue but after I replaced the IACV it ran worse and obd 505 code came on, so it obviously was junk itself so I cleaned the old one and put it back on, code didn't come back and car started but still is having a rough idle issue and after awhile the rpms will drop some and the engine will start shacking/shuddering so I won't drive it.
when I took the throttle off to clean the plate to get it all back on I had to take the idle cables off and had difficulty putting them back on so I had to induce the bolts to get the cables to reach and attach correctly, so now I don't know if I have enough slack or too much.
The gold one has been very well serviced at honda regularly as provided papers when I bought it 4 months ago. 238k
The silver one

Silvers EGR before I cleaned it.

I was able to scrap some out with the wire brush i had the could fit a inch or 2 inside... the fluid finally went through. Again silver car.
I just got 8 weeks ago came with the obd 401 code on they said they put a new egr valve on. Haven't gotten around to deal with it until it started having crazy shaking and idle issues too, within a few days as the gold one.
Obd 1399 started and flashing I took off the egr valve to discover it is filthy I clean the egr itself and the valve as good as I could with metal brush tube cleaner that thing I found with the help of cleaner also, as well as putting a gasket on as it was not put on with the egr valve. I am sure more carbon is clogged up inside.
Then obd codes 1399 flashing check engine light and 300,, 304 are now persistent. My boyfriend took it to someone he works with personal shop he spent 280$ I believe on parts, they ignored what I had said was the issue something with the EGR & intake stuff
I know they did spark plugs, coils, new oil and filter for sure, and something about I believe he said one of the cylinders underneath the spark plug isn't doing something but I don't know and it wasn't an issue before. The car still runs the exact same BAD and all codes came back plus 301.
I did a can of seafoam in the intake, it didn't smoke as much as I had expected (before when I did that on a different car it smoked a lot) but while driving and keeping the car at 3500 it actually improved for an hour maybe.
I added seafoam to the gas tank and filled it up the next day. Ive noticed I think the car is running rough and shaking when going slower speeds not noticed when on the freeway doing 50-60mph.
The silver one is actually my boyfriends and because 2 of his guy friends that work on cars say the car is done and costs too much to fix, he needs an engine junk it.
Service records did not come with it, and when I did a vin check the car sat at least a year. Silver has 175k.
I just dont understand how both cars all of a sudden have very similar issue with shaking and rpms dropping and car dying, the silver one because it is a manual is easier to start back up when it dies at a light.
Not that this has any relevance but this coincidently happened to the gold car after my boyfriend and I switched cars and he drove the gold car for maybe 2 weeks to work which in at a farm so dirt roads. Then when gold car dies at the light he took the silver car back and to work again in on dirt roads and within days started all the issues.
I don't believe his friends both cars did not just crap out the same week and needs new engines...