Mechanics

ROUGH IDLE IN DRIVE, DECREASED FUEL ECONOMY

2004 Honda Jazz • 80,000 miles

Our Honda Jazz (vtec, auto) has been at the mechanics every couple of months for the last year with this same problem. When the engine is cold, it idles rough and almost stalls, only when in drive (park, reverse and neutral are fine). When slowing down, close to 1000RPM's, the engine splutters and again almost stalls. Sometimes when taking the foot off the accelerator the car runs smoothly for a bit and then******, almost like it's suddenly switching to a lower gear suddenly. Accelerating, the engine runs fine. We have had the flywheel replaced (no improvement) and have had the valves cleaned (no improvement). After numerous trips to Honda, they keep giving it back with no improvement. When the idling is very bad we also notice the fuel economy drop to less that 9Km/ltr (at the best of times it's not better than 11km/ltr). So we're not sure if it's because of this problem. Any advice would be appreciated
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Johden
September 5, 2011.




This could be several things. Have them check for tune up, check for vacuum leaks, check idle air control valve, check to make sure O2 sensors are functioning properly, check catalytic converter for plugging. Any of the above can cause this issue. Also, if the check engine light comes on, have the computer scanned at a parts store. Most will do it for free. THat way you will know what trouble code is the issue and then we would be able to be more specific with our diagnosis. As far as some of the things they did, I don't understand. The flywheel wouldn't have anything to do with a rough idle.

The check engine light is not on and has never turned on at all anytime we have had this problem. Does this change any of the suggestion you have made so far? We have booked the car in with Honda again this wed, and will ask them to check the things you have suggested. If there is anything else you feel would be good to have checked, please let us know so we can tell them. Will let you know how it goes. Thank you again for your advice.

Tiny
Johden
Sep 5, 2011.
If the valve clearances had not been checked/sdjusted for a while, get it done.

KHLow2008
Sep 5, 2011.
It would have been done about a year ago. Do you think we should ask them to do it again anyway?
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Tiny
Johden
Sep 5, 2011.
If the valve clearances are too tight, it would result in surging and rough/erratic idling and since you are having problems with rough idling and high fuel consumptiom, I would suggest getting them to check again.

KHLow2008
Sep 5, 2011.
We went to pick up our car today and were told that all the things that were on the list of things suggested to fix had been done before, and were checked again. And no improvement. They then told us that we would need the whole gear and transmission box replaced (which would cost a fortune - may as well buy a new car). I asked them to write down exactly what they checked and the results of what they checked (which I would then let you know) and so he said he would do that for me. The car is still at Honda today and hopefully we'll be able to pick it up this afternoon. I am not entirely sure if they actually pulled everything apart to check everything or just looked at the list of problems/symtoms and decided that changing the entire transmission and gear box would just be easier. The reason why the car is still at Honda now is because we spoke to the manager and he's seeing if there is something else they can do now (Hmmm). Do you think that the symptoms presented would warrant changing the entire gearbox and transmission? I felt it was a bit extreme (not to mention the cost) given that the problems occur mostly only when the engine is cold, not all the time. Then again, my feelings mean nothing given I know nothing about cars. I also do not know if this would have bearing on the fuel consumption either.
Just to let you know, we are in Thailand, so when we get the list of things they have done, I'll be translating it from Thai and not being a mechanic at all, pls forgive me if I don't get all the technical terms. Will let you know how we go.

Tiny
Johden
Sep 8, 2011.
I rechecked through all the things that you have mentioned and I would still say it is something to do with the valve clearances. Most probably the clearances have been adjusted wrongly.

The symptoms do not indicate a fault with the transmission and it is the engine that is behaving erratically and does not do so when gears are engaged. Fault lies with the idle control and mechanically, the valve clearances is one of the most likely cause. Components linked to the idling would be the PCM, throttle plate clearances, IAC, idle adjust screw and its passage. An out of range O2 sensor can cause such problems too.

Since the engine is not running well, it definitely would affect the fuel consumption as the PCM needs to keep changing its mixture from lean to rich and vice versa.

KHLow2008
Sep 8, 2011.
Thanks so much for all your help. I REALLY appreciate this! When we picked up the car today, the manager had already left for the day so we were not able to speak with him directly and there were no details written down as to what they had checked in regards to what you had suggested we have them to check (even though I had specifically asked them to - no surprise!) The guy at the front desk just said that they had not done anything with the gear/transmission - so I am assuming nothing has changed in that department. They had however changed all our wheel bearings which they said were very worn (?) And adjusted something on the brakes (all for free!)When I drove it out of Honda, it had the same problem of rough idle/rough when it got close to 1000RPM (because that wasn't fixed), but I also felt like the brakes were on all the time especially when you start to slow right down (like the car doesn't just "roll"). Is this because they'v overtightened something on the brakes now? It definitely feels different to before when it felt like the car would change into a lower gear. Almost more "sluggish" when going slow. We're going to drop in tomorrow morning and talk to the manager face to face and I will insist that he check the valve clearances if he did not do it this last time. If you think we should get him to recheck the brakes again, I'll get him to do it at the same time. Thanks again for all your advice! I will let you know how it goes.

Tiny
Johden
Sep 8, 2011.
Yes, it is possible something is wrong with the brakes adajustment or it could be that the brake calipers are bad and not returning fully causing the brakes to be partially applied. One way of testing is to drive slowly and shift the transmission to neutral and allow the vehicle to coast to a stop on level ground. If the brakes are holding, the vehicle would not coast but instead try to stop as soon as possible and at the final instance, you would feel the vehicle******** slightly to a stop.

KHLow2008
Sep 8, 2011.
Some better news today.
My husband drove the car for a bit last night and we also drove the kids to school (round trip 24kms) before going back into Honda to speak to the manager. The brakes seemed much better this morning and the idling was better (only felt like it was just about to stall once) when stopped at the lights. We spoke to the manager at Honda who told us that they did clean the valves which were very dirty and looked also at the gear system and 02 sensors. Because we needed the car Friday and the weekend, he was not able to get another mechanic in yesterday for him to look at it and get a second opinion. So we're going to drop the car in again Mon-Tues next week so this other mechanic can look at it. The manager was good today in that he said he wanted to check all other options before having to do "major surgery", and we asked that on Monday to have the valve clearances checked as well, which he said he would do. If the brakes play up again, I'll mention it to them too.
Thanks again for all your help. Will let you now next week how things go.

Tiny
Johden
Sep 9, 2011.

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