Mechanics

RPM CHOKE WHILE BRAKING

2007 Honda City • 4 cylinder 2WD Automatic • 60,000 miles

I'm driving a Honda City V-tec 2007 model. Recently the car has some problems with unstable rpm caused the car choking while braking the car in traffic flow slowly. This choking incident will cease when I change the gear status from "D" to "N" condition. This incident will happen only intermittent.
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Eefish
August 10, 2011.




When was the last time the spark plugs were checked?

KHLow2008
Aug 10, 2011.
I just changed the spark plugs last month ago. I had been trying this few days and this problm was appear again. My car start choking up & down while stopping in front of traffic light or braking with gear "D" condition. Anything goes wrong with my gear box?
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Tiny
Eefish
Aug 12, 2011.
The engine is surging when brakes are applied. This indicates you have a possible vacuum leak in the brake booster which would increase the rpm and when the engine computer senses it, it would try to reduce the rpm. The cycle would repeat so you need to have the brake booster checked.

The most common cause of vacuum leaks would be a bad seal between the master cylinder and booster. If you pull the master cylinder out slightly, ( need not remove any hoses) you would see the seal. Ensure the central portion is not worn or torn.

KHLow2008
Aug 12, 2011.
Hi KH,

This is really new to me. I just went back to Honda SC last Sat (12th Aug) to clean the Throttle body but it's seem not much improvement for rpm unstable and choking issues. After digested your below statement, I also realised that my braking system was too agressive & over react in a very short period until I can't managed it well. I felt my brake is over agressive nowaday without changing any new brake pad. I will go back to SC this coming Sat for another check-up on my brake booster & hopefully this is a real root cause for engine surging issue.

Tiny
Eefish
Aug 16, 2011.
If the rear brakes are locking up too fast, the front calipers are most likely not functioning correctly. The slider bolts or caliper pistons could be stiff/partially stuck.

Choking until engines seems to stall could be due to tight valve clearances if the throttle body is clean. Was the IAC cleaned by removing it from the throttle body? If the rpm is surging, then it is a possible vacuum leak.

KHLow2008
Aug 16, 2011.
Hi KH,

Thanks for the valuable info shared as per below.

I’m getting a little bit confused now. From the points of you, what should be the correct steps & actions I need to get SC mechanic to do? Check the brake booster to ensure there are no vacuum leaks thru the seal between the master cylinder and booster or just need to perform check & cleanup the IACV sensor, reset ECU needed? I’m not sure whether the mechanic engineers can fully understand my car problem when I’m trying to tell them all these issues later.

This issue had been annoying me few days while driving the car at traffic congestion condition. I really need to solve this problem with right approach otherwise I might spend more time and money of changing the spare parts without any final solution.

I hope you can provide me more concrete method & step of screening so that I can explain and lead them to the main root cause.

Appreciate very much your help and patience with me.

P/S: I tried to brake my car gentlely this morning. It seems like the choke not so obvious now. The choke also happening when I tried to reverse my car with rush braking.

Best Regards

Tiny
Eefish
Aug 17, 2011.
Since braking is affecting the engine idling, I would suggest starting woth that. Check for vacuum leaks with brake pedal depressed. Once you have the leaking rectified, I believe the idling should get back to normal, ubnless you have a fault with the IAC, which could be dirty internally.

KHLow2008
Aug 17, 2011.
Messsage noted. Let's see what is the finding after my 2nd round check with Honda SC this coming Sat. Cheers

Tiny
Eefish
Aug 18, 2011.
Hi KH,

SC had checked my brake booster and confirmed that there is no vacuum leak issue. They also re-check and re-clean the throttle body and IACV sensor for me & everything’s seems alright.

They went thru the computer diagnosis analysis with me, all data collected are positive but they found some noise when they changed the CVT gear box from “N” to “R”. They suspected the noise is come from the flywheel and it will also cause the RPM***** & surge.

They had quoted me total cost RM1160 to change the whole flywheel.
I was there when they try to prove me the noise and I feel very minimum rough gear transition and******** when changing to reverse gear.

I still yet buyoff his idea due to he can’t guarantee my problem can permanently fix after changing the flywheel.

I would like to hear from you what is the next step & action I suppose to do now?

Thks

Tiny
Eefish
Aug 23, 2011.
If the transmission fluids had not been replaced for an extended period of time, have it replaced and retest. Bad transmission fluids can cause surging when the chain in the CVt transmission slips.

KHLow2008
Aug 23, 2011.

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