Having some car trouble, could use some input
February 28, 2014 10:03 AM   Subscribe

So my 2007 Honda Fit has been having these weird issues while at stop lights or stop signs and I can't figure out what's going on.

When we're stopped, the engine RPM will dip from 1000 to 500 briefly and the engine will 'chug.' Like some sort of shudder or something like that, surging a little.

We took it to the shop about this and a flat tire about a month or so ago and they changed the cabin air filter, did something to the throttle body, changed the tires, and looked over the whole thing. They didn't see any issue with the spark plugs and would have done something if they did.

What I so know, though, is that the when I'm braking at higher speeds (40+ MPH) the car will shake and rattle a lot. I talked to the mechanics about this and they said it was an issue with eh brake rotors being slightly warped. It's not severe enough that I lose control of the car or anything; it's just annoying. But I don't know if there's a chance of those things being related in any way.

Any advice would really be appreciated.
posted by Modica to Travel & Transportation (13 answers total)
The former issue does sound like it could be plugs, or another electrical issue. Does the check engine light not come on? I take it you are still having the issue after the service? I would probably take it into someone else for a second opinion. Or you could just switch the plugs out anyway, spark plugs are cheap. It's kind of hard to guess why you might have a rough idle if the system isn't throwing any codes.

If your rotors are warped enough that the car is shaking when you brake, you need to replace them.
posted by selfnoise at 10:15 AM on February 28, 2014

Nope, no check engine light.

One other thing, when these chugs or surges happen, the headlights also briefly dim then return to their full brightness. Dunno if that's important to note or not.
posted by Modica at 10:18 AM on February 28, 2014

Additionally, now that I'm thinking about it, the problem with the shuddering wasn't showing up after the service till recently, till it started getting warmer again. It was worse, too, when it was warm and less noticeable in the cold.

Sorry for all the stuff I forgot to mention, wasn't really thinking about it.
posted by Modica at 10:27 AM on February 28, 2014

But I don't know if there's a chance of those things being related in any way.

No, there isn't. For reference, your brake discs are not actually warped per se (urban myth) but there is an inconsistent layer of brake pad material smeared onto the disc from the brake pad. Perfectly normal and usually hard braking will clean that stuff If the build-up over time becomes too much to remove with hard braking (ie too much of your driving is gentle braking percentage-wise), then it needs to be removed (an easy enough job) or the disc replaced.

I wish people - especially mechanics who should know better - would stop propagating this 'warped disc' rubbish. It's almost impossible to actually physically warp a brake disc.

when these chugs or surges happen, the headlights also briefly dim then return to their full brightness.

More symptoms, but not useful ones. The headlights dim because the rpm drops and the alternator (whose output is dependent on engine speed) drops. So the only issue you have (plus a bunch of resulting effects) is the engine revs dropping. This could be almost anything electrical or fuel related in the car and will be difficult to diagnose without further information or testing.

When we're stopped, the engine RPM will dip from 1000 to 500 briefly and the engine will 'chug.'

If this can be reproduced reliably (ie you can make it do it or accurately predict when it will happen) then that will be useful for the mechanic to diagnose. Is it always in the hot weather, or cold, or after a long drive at steady throttle, or it only does it after 10 seconds of idling. Any repeatable parameter will be useful. It could be a sensor that is giving odd readings and the engine loses rpm until the ECU decides the signal is far enough out of parameters to ignore it and then 'rescues' the engine rpm by either disregarding that sensor or switching to a different map. Or a vacuum leak. Etc., etc.

basically, it's impossible to diagnose without a lucky guess. I suggest you give some critical thought to trying to spot patterns in when the fault occurs and give as much information as you can to the mechanic when you take it in next time - making sure he can replicate it is key for them to be able to diagnose it. Intermittent faults are things evrey mechanic hates because they never seem to happen when the mechanic is driving.
posted by Brockles at 10:27 AM on February 28, 2014 [1 favorite]

It was worse, too, when it was warm and less noticeable in the cold.

That is normal - differential expansion of the pad material and the disc will mean temperature is a factor.
posted by Brockles at 10:28 AM on February 28, 2014

I imagine you have, but - did you get all your recalls done? Have you checked for any new ones?

I remember a friend of mine had trouble with her Fit and had to have a bunch of wiring replaced, and it was related to one of the recalls. (Whereas my Fit has had the recalls completed and is fine.)
posted by needlegrrl at 10:29 AM on February 28, 2014

I had a similar issue with my 2006 Element. After looking at everything they could think of, I had them adjust the valves based on an entry I read on an Element board. This turned out to be the fix I was looking for. This happened at 55K and again at 110K. When I went in for the second one, my mechanic mentioned that they had seen the same thing in a lot of other Hondas after mine. As far as I know there was no recall or even a service bulletin, so this may not be on every Honda mechanics radar.
posted by doctor_negative at 10:33 AM on February 28, 2014

I actually don't know about the recalls. We got the car from her dad (it was his old car) about six months ago. I'm going to check on this.
posted by Modica at 10:35 AM on February 28, 2014

These sound like two different problems, I really don't think they're related. I can't speak to the second problem, but I did see the first problem a number of times when I owned a Honda POS**:

- air idle control valve (air idle valve / sensor) (AIC or AIV, has many names)
- exhaust gas recirculation valve (EGR) (this is a valve added for environmental reasons)
- alternator (dimming lights only)

If you are in any way mechanically inclined, you can clean the first two very easily, just google around for instructions. If you're not a quick trip to the mechanic will fix it ($100-$200 is what I paid I believe, the part is a little pricy for what it is but easy to install).

PS. If you're short on cash, next time never pay a mechanic to change your air cabin filter. In hondas they are easily located behind the glove compartment. It can be done in 2 minutes, there are many youtube videos showing how to do it.

**piece of sh*
posted by St. Peepsburg at 11:00 AM on February 28, 2014

My Fit had something similar a few months ago. No check engine light was on, but it was one of the plugs. Their OBD test saw the error.
posted by toddst at 12:24 PM on February 28, 2014

Another thing to look at: the Fit has a tiny battery. It's not much bigger than the battery that goes in a motorcycle. My '07 Fit had a few issues with the headlights dimming and some hesitation and it was solved by replacing the battery, which didn't quite fail a load test but was borderline.
posted by zsazsa at 2:21 PM on February 28, 2014

Could be symptoms of a failing or contaminated mass airflow sensor to me. When they did all this stuff to your car in conjunction with the flat tire fix, did they happen to change the oil? I'm of the understanding that sometimes when they replace the oil and are a bit generous with it, it can contaminate the sensor and it'll cause the engine to run too lean/rich, shudder, etc.

My old Cobalt had warped rotors and would transmit some shake through the wheel when braking. If the rotors aren't too far gone you can have them machined fairly cheaply. If they are, they shouldn't be prohibitively expensive.
posted by area.man at 10:07 PM on February 28, 2014

If you're not having much luck with your mechanic, the best place to post Fit questions is on the Fit Freak forums. The members of that board know Fits inside and out and are very helpful.
posted by gfrobe at 8:05 AM on March 2, 2014

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