Rough idle in drive, decreased fuel economy

Tiny
JOHDEN
  • 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

Do you
have the same problem?
Yes
No
Monday, September 5th, 2011 AT 2:30 AM

19 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
  • 68,336 POSTS

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.

Was this
answer
helpful?
Yes
No
Monday, September 5th, 2011 AT 2:41 AM
Tiny
JOHDEN
  • MEMBER

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.

Was this
answer
helpful?
Yes
No
Monday, September 5th, 2011 AT 8:55 AM
Tiny
KHLOW2008
  • EXPERT
  • 42,002 POSTS

If the valve clearances had not been checked/sdjusted for a while, get it done.

Was this
answer
helpful?
Yes
No
Monday, September 5th, 2011 AT 2:23 PM
Tiny
JOHDEN
  • MEMBER

It would have been done about a year ago. Do you think we should ask them to do it again anyway?

Was this
answer
helpful?
Yes
No
Monday, September 5th, 2011 AT 2:31 PM
Tiny
KHLOW2008
  • EXPERT
  • 42,002 POSTS

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.

Was this
answer
helpful?
Yes
No
Monday, September 5th, 2011 AT 3:36 PM
Tiny
JOHDEN
  • MEMBER

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.

Was this
answer
helpful?
Yes
No
Thursday, September 8th, 2011 AT 6:02 AM
Tiny
KHLOW2008
  • EXPERT
  • 42,002 POSTS

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.

Was this
answer
helpful?
Yes
No
Thursday, September 8th, 2011 AT 1:20 PM
Tiny
JOHDEN
  • MEMBER

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.

Was this
answer
helpful?
Yes
No
Thursday, September 8th, 2011 AT 3:44 PM
Tiny
KHLOW2008
  • EXPERT
  • 42,002 POSTS

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.

Was this
answer
helpful?
Yes
No
Thursday, September 8th, 2011 AT 6:27 PM
Tiny
JOHDEN
  • MEMBER

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.

Was this
answer
helpful?
Yes
No
Friday, September 9th, 2011 AT 3:01 AM
Tiny
JOHDEN
  • MEMBER

YAY! Thankyou so much for your help! We picked up the car and it's PERFECT! No rough idle, no feeling like it's going to stall, no sticky brakes and the car feels like new! Strangely, when we took the car in on Monday, the car was running beautifully, with no hint of feeling like it was going to stall, even though on Fri-Sun it was still idling quite roughly. I don't know if it takes time after cleaning the valves for things to "clear through" or did something just "fix itself"? Either way, when we picked it up after the service, the mechanic did say that they had rechecked everything and readjusted the valves and O2 sensors. We did not get to speak to the manager again to find out what exactly was the problem, as he had already left by the time picked up the car, but are very grateful that it is running beautifully now. Now we're seeing if the fuel economy improves. We filled up as soon as we got the car back and so far we've done over 130kms and the fuel needle has barely dropped (previously it would've dropped about 20% already). So fingers crossed.
Again we want to thankyou from the bottom of our hearts for your advice. Thankyou!

Was this
answer
helpful?
Yes
No
Thursday, September 15th, 2011 AT 3:04 PM
Tiny
KHLOW2008
  • EXPERT
  • 42,002 POSTS

Glad to hear the good news.

Have a great day.

Was this
answer
helpful?
Yes
No
Thursday, September 15th, 2011 AT 8:24 PM
Tiny
BURNER_18
  • MEMBER

Hi Johden,

did you find out what they did to fix the problem. I have the exact same problem. PLease HELP !

What was the exact cause of the problem

Was this
answer
helpful?
Yes
No
Saturday, August 4th, 2012 AT 6:41 PM
Tiny
JOHDEN
  • MEMBER

We had the whole thing re calibrated, cleaned out, re-tuned. But about 4 weeks later the problem came back and the fuel economy dropped back to what it used to be again. We did take it back and the mechanic basically said they couldn't understand what was going on. They suggested we replace the entire gear box next which was going to cost a bomb. Because of all the troubles we had with this car, we decided to just get rid of it and get a new one. It ended up being cheaper to trade it in and buy a brand new car than replace the entire gear box! Sorry to hear you've got the same problem. One person did mention to us that that this particular model needed a specific type of engine oil that only Honda produces. Any other type of oil wrecks the engine. I have no idea how true this is, but you may want to look into it? Hope you can get to the bottom of it. We weren't able to

Was this
answer
helpful?
Yes
No
Sunday, August 5th, 2012 AT 2:25 AM
Tiny
KHLOW2008
  • EXPERT
  • 42,002 POSTS

I had almost forgotten about this and lately I had the chance to do a diagnostic on a vehicle with similar symptoms.

O2 sensors etc and many other components were tested but finally the part that made a chage was the EGR system which showed no trouble codes. Replacement of the EGR valve (used part, twice)and cleaning the ports did not solve the problem of the rough idle and struggling at low speed, within the range of 1000 to 2000 rpm.

Disconnecting the EGR solenoid wire connector stopped all the problems and after that the vehicle was taken back by the customer as he had to go out state so I did not have the chance to rectify the problem. When the vehicle left it was with the EGR not connected and customer did not call back to say anything so I don't know how it goes.

From above, I gather it is the EGR system that is causing the problem and could be a PCM fault.

Was this
answer
helpful?
Yes
No
Sunday, August 5th, 2012 AT 4:21 AM
Tiny
BURNER_18
  • MEMBER

Thanks for your advice Johden,
Its unfortunate that you had to trade your car and we really didnt get a definitive solution.

KHLow2008,
Explain Disconnecting EGR solenoid wire connector?
I have changed the EGR valve.

Was this
answer
helpful?
Yes
No
Sunday, August 5th, 2012 AT 4:32 AM
Tiny
KHLOW2008
  • EXPERT
  • 42,002 POSTS

At the EGR valve, unplug the connector and retest.

Was this
answer
helpful?
Yes
No
Sunday, August 5th, 2012 AT 4:39 AM
Tiny
BURNER_18
  • MEMBER

Ok, I will try that tomorrow, although I think I have already.

My problem is that when the car is cold and I drive out and stop/idle in traffic the engine vibrates violently. Its worse when the a/c is on. Funny thing is that when the car is really warmed up, it will smooth right out. Since recently it has gotten worse though.
I have so far changed EGR, TPS, IAC, throttle body, o2 sensor, air temp sensor, Coolant temperature sensor and Tried another map sensor, catalyic converter replaced, I have changed air filter, gas filter, honda ngk plugs, honda oil and oil filter, honda CVT Transmission oil. I have also changed all 8 coil packs.
I think thats everything that has been replaced. Not sure where else to look at this point.

Was this
answer
helpful?
Yes
No
Sunday, August 5th, 2012 AT 5:00 AM
Tiny
KHLOW2008
  • EXPERT
  • 42,002 POSTS

Were the valve clearances checked?
You might need to have the PCM updated if it does not have the latest software. That would mean a visit to the dealer.

Was this
answer
helpful?
Yes
No
Please consider a donation if we helped you
Sunday, August 5th, 2012 AT 5:16 AM

Please login or register to post a reply.

Related Engine Poor Mileage Questions

Recommended articles