Ardee99

I have been trouble shooting a choppy/surging/rough idle for the last week. The CEL is on. When I pulled the code it is a 14; Idle Air Control. I have had this same code in the past but I have been able to pull the IACV and clean it out and had success. It got to the point this would no longer work so I purchased an OEM IACV, but it did not correct the issue.

The idle would only get bad after the car achieved temperature and after traveling. If i just let the car sit at temperature and never drove it then idle would never change. If the ilde was choppy after driving I shut the car off and turned it back on the idle would go to 1500 then drop down to 1000 and stay steady. It would become really bad surging to 1700 and staying at 1700 and make an awesome popping sound coming from the exhaust when ever I set at a stop light.

So I began my investigation;

I bled all the air out of the cooling system (6 months ago I changed all belts, including the timing belt and replaced the water pump) I never bled the cooling system after performing this maintenance. Still no success.

Next step I began checking the system for vacuum leaks. I used the carb cleaner method on a cool engine. I also tried the water method. I can't find a vacuum leak.

So today for some unknown reason while I was sitting in the car watching it idle nicely at 1000 with CEL on, I decided to press on the break peddle. When I let off the brake peddle the idle jumped to 1300 then back down to 1000 and stayed steady at 1000. I pressed the peddle again, same exact thing. I thought maybe I just had good peddle pressing timing, with the surges. So I waited a little longer and stepped on the peddle. Same exact thing. So I then began to pump the brake peddle, as if I was revving the car, the idle climbed and climbed to 2000 then the computer system kicked in and the idle began fluctuating from 1000 to 1700 for a 15-30 seconds then settle back at 1000. This would explain when i set at a stop light for an extended period of time with my foot on the peddle the idle would surge to 1700 and stay stuck. The surges are caused by me pressing on/or holding my foot on the break peddle

So after my story I shared, in the hopes it would help others, my question is... do I in fact have a vacuum leak and if yes, is it in the break system? If yes what vacuum line would this be?

If NO what should I begin to trouble shoot next?

As always thanks for everyone's replies, please feel free to ask all the questions you need too

Former User

Test the check valve to the brake booster and the booster itself.

Ardee99

On the diagram it days check valve built in. Just want to confirm, built in means that check valve is inside the hose, correct? To check the valve I follow the procedure in the diagram.

Also I have attached a photo can you tell me what this guy is?




If I hit this guy with carb cleaner while pumping the brakes the car dies. If I hit it with the carb cleaner without pumping the brakes there is no change in the idle.

Former User

Fuel pressure regulator

Do the tests.

Ardee99

I will have a follow up reply tomorrow. Off to bed now, up for work at 4am. Thanks Ron J

Former User

Valve is built into hose.

Ardee99

Follow up on the booster pump and booster pump check valve. Everything checked out OK There is plenty of vacuum on the line. When I started the car with the vacuum line unhooked it hit 2500. Once I put my finger over the opening to check for vacuum the idle went to 1000 to 1500 then to 1000 and settled at 1000. Once I hit the brake peddle it had the same reaction would bounce back and forth to 1500 to 1000 and then settle, suction on the line never decreased. I hooked the line back up and everything remained the same. I had a helper just FYI

If I disconnect the IACV sensor the car idles at 800 and acts normal with the exception of pushing on the gas peddle and letting off is a little jerky, but I don't have any issues at all with the idle fluctuating.

So I am at a loss once again..... anything with the comment on me being able to kill the car with the carb cleaner if I spray the fuel pressure regulator with it?

Ardee99

Bump

Ardee99

More info in hopes of more help....

I notice the idle surging to be at its worst when the car reaches temperature. After driving the car on the interstate for an hour or so, when i get off the exit and begin driving at a much lower speed say 25-35, the car will jerk violently.

As i stated before if I unplug the IACV sensor the surging stops and the car drives fine. Today I unplugged the sensor before I began my drive home on the interstate. Again idle was normal. However when I get off the interstate the car began to jerk violently just like it has in the past.

Any recommendations here? Trying to tie this all together. Again the only code is idle air control, 14

PJHennessy203

check your CFIV. This corrected my surging idle. Watch the whole video its very informative and shows you what to do.

Ardee99

Thanks for the reply. I am guessing you are referring to the Cold/Fast ICV. With my Honda being a 99 it doesn't have a FICV. Correct me if I am wrong, but I don't believe my motor contains this.

Keep the recommendations coming