Hi everyone,
A couple months back I bought a used 2001 Honda Accord LX (4-cyl engine) with 150k miles on it. Recently, Ive been experiencing some idle issues with the car and I've also noticed that the fuel economy is pretty garbage.
When I try to accelerate, the RPM will remain stagnant for a lil bit and after a few seconds it starts to climb normally. Then, when I'm above 2500 RPM and I try to reduce speed or stop the car the RPM will plummet and sometimes surge, fluctuating between 1000-1500RPM for just an instant. The CEL codes that have popped up are a P0172 code (system running rich) and a P0420 (catalytic converter below efficiency threshold). Could the system be running rich due to a problem with the fuel system (i.e., clogged fuel filter, clogged fuel injectors or some other fuel system failure) or could it be running rich from a vacuum leak? It should be noted however that after a few days the check engine light turned off without me having to connect the scan tool.
I also recently noticed that the car is running with rust in the coolant when I went to check the coolant level. When inspecting the coolant lines I noticed that there was one going to a part in the throttle body (just below the intake inlet) that seemed off color. When I removed the line I saw that the tube connecting to it was badly eaten up by rust. I don't know if this is the sole culprit of the rust in the coolant but its definitely a place to start. I dont know exactly for how long this has been going, but it seems like it could be potentially dangerous if left unchecked. The coolant is no more than 3 months old and Ive barely put 3000miles on the car since I bought it.
Can anyone here offer some sort of advice on how to diagnose the idle and poor fuel economy problems? And how should the rust issue be approached? I imagine a flush is in order, but what would be the best way to do it and what should I be aware of?
Find the MAP sensor and carefully inspect the air hose(s) from that point to the throttle body.
Had cars develop an air leak near the throttle body and cause stalling and very rich exhaust problems.
Yeah that was the first place I was going to check. I already had planned in the next months a thorough throttle body cleaning, but I guess I'll have to move that up in my calendar and get it cleaned earlier. I imagine, that while I'm at it, I should take the chance to remove the whole intake (manifold included) to give it a much deserved cleaning and replace the seals and gaskets for new ones.
However, lets say the idle persists after that, what sort of problem could the idle be pointing towards if its not a vacuum leak? Fuel system maybe?
Also, what should I do about the rust? Would you happen to have an idea of the name of the part in the throttle body that has coolant going through it? I dont think its a fast idle thermo valve (FITV) as a friend of mine had suggested, since Im pretty sure Honda shied away from that particular design after the 5th gen Accords.
No idea about the rust. Found this link too:
https://www.700r4transmissionhq.com/p0172-honda-accord/