Surging Idle, and other misc problems
 

so, without getting into why, I've had my car sitting for a month and a half doign nothing.

I finally used it again today, and my idle was surging like mad.

when in neutral it will surge from about 700 to 2500, then fall then do teh same thing.

other times it will bounce at around 2000 rpms like a rev limiter except instead of preventing it from exceeding a certain rpm, it prevents it from going below 2000, lol.

when I'm in gear and stopped it is like I'm giving it a tiny bit of gas when I'm not. it jumps from the line as soon as I let go of the brake. Someitmes it surges when in gear too.

I've also had it do that rev limiter shit while I was moving in third gear and coasting, which I'm sure is really bad for the trans.

I also got the P0505 code (idle control system error) or some crap on my CEL after driving it like that for a bit.

Just off the top of my head I want to say IACV, or vacume leak, but will a vacume leak cause a surge? I figure a vacume leak would just cause a high idle.

my helms says it could also be the Coolant temp sensor, or the throttle position sensor, but I think the TPS is fine since my VAFC reading of my throttle % is pretty accurate.

I unplugged the IACV and it still does that inverse revlimiter shit at 2000 rpms.



Also, my rear brakes are makign this load groaning noise when I use them. didn't do this before the 1.5 month downtime. Could it just be the rust on the rotors? Should I just drive it a bit more to see if it goes away on its own?


Any help or suggestions woudl be highly appreciated.

vacuum leaks can cause idle surges, but i dont think thats your problem.

ok, just drove it a bit more, adn it seems that when I'm driving and I let off the gas, it will do it's normal engine braking until about 1100 rpms and then it will jump up to around 1500-2000 rpms and cruise like that, as if cruise control were on or something.

very weird, and it's pissing me off.

I'm gonna pull off the IACV tommorow and clean the shit out of it.

mine does that sometimes, and one day i was messing with my throttle body spacer and it did it like mad, its worth a try to check the seal on your tb also

Did you drive around with your IACV unplugged? If so, then that will most likely be as to why your CEL came on.

As for the brakes, a little brake parts cleaner will do the trick to get the rust off (assuming it was left outside and it rained or snowed on it).

The rpms surging up and down def sounds like the IACV. As to why it wont drop, I was having that issue before as well, but dont remeber what the answer was.

so I pulled off the IACV today, adn sprayed the shit out of it with carb cleaner, same problem, so I just ordered another IACV for $107 :ugh:

I guess I'll just see if that fixes it.

I'll try cleaning off the brakes with the brake cleaner, and see if that fixes teh excessive shakking/groaning.

honda lube or brake cleaner for the brakes.

Mine does something similar. When I am coasting downhill around 1500-2000 rpms the car slows down and acts like I am braking. I also hear a slight hum when this happens. If I tap the gas at all it will stop slowing down and resume normal coasting. If I dont tap the gas and let the car slow down after a while it will all of a sudden resume normal coasting. Is this normal or something I should be concerned about?

small update on symptoms that might help me resolve my issue.

When I'm driving in 4th gear, it seems like when I completely let off the throttle the engine braking is more intense than usual., and if I give it any less than 5% throttle it doesn't change, it continues engine braking, but as soon as I give it more than 5% it JERKS and starts accelerating, or at least cruising.

Could it be the EGR?

did you bleed the coolant system? its definatley the iac. like when you come to a stop it feels like your pushing the gas and the brake at the same time? remove the radiator cap (when cold) sart the car let it run till the thermostat opens. that usually is enough. but you might have to loosten the bleed screw.

thanks wilp, I'll try that with the coolant system tommorow. I already ordered a new IACV, so hopefully if the coolant thing doens't fix it, this will.

it was the IACV, replaced it and it went away along with hard/shuddering shift problems I had.

good shit, how clogged up was the old one.

if it was just clogged you could have saved yourself some bills.

I had already pulled the old one and cleaned the shit out of it with carb cleaner, it must have been the motor that failed.

ahha cant be the motor.. you just told us that it the IACV. but o well w/e good job =]

wow.. soo sorry i forgot to check the date x_X

Had surging idle. My fix was vacuum leak out of $8.00 rubber pvc gromet.
Do your own smoke test. See youtube. Worked for me.
Replace iac valve only if verify error code, - make sure honda acura part. Do not use off brand imho.
Very small chance its your motor mounts.
Do the air bubbles out of radiator. - especially if you remove throttle body for cleaning.
Easy things that will help performance while your at it.. Clean egr passages and valve.
Change plugs- only took me 20 minutes and cost 20.00. 2003 tl has 135,000 miles and runs great.
.

I use to have the same problem, glad you got it fixed. I think I literally just plugged up my IACV with epoxy. OR maybe what fixed it was the plenum gasket. I cant remember it was too long ago. It's pretty easy to find leaks if you have some carb cleaner :thumbsup:

Had similar issues
 

I purchased my 97 with a 3.0 rust free but sitting in mud with the exhaust completely rusted off. Otherwise a nearly new looking car.

The dealership took it in on trade and couldn't fix the issue, I fixed it by using a breaker bar and a hammer to tap on the electric motor on the IAC valve. Sometimes they get rusty inside the plastic housing due to design, and they also coke up from carbon. Other than replacement, you can try either tapping it every once in a while lightly with a screw driver, or take it off and clean the piss out of it.

I still haven't replaced mine, only reoccurs every once in a blue moon during cold winters (10 degrees or less) and quits once warmed up.