NC rough idle

locksmack · Postby **locksmack** » Sat Oct 12, 2013 10:41 pm

Hey guys,

I test drove an NC on Thursday that I ended up buying. During the test drive I noted to the dealership that the engine was idling a bit rough - it seems to jump between 750 and 1k rpms every few seconds. Otherwise it felt smooth during acceleration.

I noted this to the salesman who said he would get the workshop to take a look. He called me yesterday and told me the mechanic reckons it was a but rough because the car was cold when we took it for the test drive, but it would stabilize once warmed up. Unfortunately I didn't check the idle at the end of the test drive so I'm not sure if that is true.

What do you guys reckon, is this normal like they say? I am supposed to pick up the car on Tuesday but have been stressing that there might be something wrong and kicking myself for not investigating further. Being a dealership, the car comes with a warranty.

The car is an NC1 with 52k kms on the clock. I'd love some opinions on this to put my mind at ease. Thanks

Old Dude · Postby **Old Dude** » Sat Oct 12, 2013 11:00 pm

it could be dirty injectors, or even an air filter. I would go for another test drive before handing over the money and if its still there don't collect it until its fixed.

Cheers
Dale

taminga16 · Postby **taminga16** » Sat Oct 12, 2013 11:17 pm

Ask them to FILL the tank with Premium fuel and tell them that you need it for an afternoon, 4500 RPM would not be too hard on it, if it is still rough and hunting and the dealer cannot sort it find another one. PCV's, vaccum leaks or a dirty air filter could be contributing to the symptoms described.
Greg.
My bike hates old fuel!

JBT · Postby **JBT** » Sun Oct 13, 2013 6:13 am

locksmack wrote:......I noted this to the salesman who said he would get the workshop to take a look. He called me yesterday and told me the mechanic reckons it was a but rough because the car was cold when we took it for the test drive, but it would stabilize once warmed up....

You may need this when you next see the dealer:

Our NC1 has nearly 80,000km on it and it has never done this. It starts and runs smoothly under all conditions from extremely cold to bluddy hot, whether it has been used daily, weekly or been left sitting for a month. I can't say I've ever heard of anyone having such a problem with this model.

If I were in your position, I would consider using the "cooling off" part of the purchase contract to cancel the contract, reject the car or request your deposit be returned until it is running to your complete satisfaction. There are plenty of alternative cars on the market.

At a minimum, stand your ground and go no further with the purchase until they do what taminga16 suggested. It should idle smoothly at all times and run out to 6000 RPM through the gears - watch your speed though. :wink:

JBT · Postby **JBT** » Sun Oct 13, 2013 7:52 am

Just to clarify a couple of things:

The tacho markings are every 125 RPM over 500 RPM.
When ours starts from overnight cold, the revs go up to about 1800-1900 initially and then fairly quickly start dropping to around 1500-1600 and then settle at normal idle speed of 750 after about 2 minutes.
Normal idle when warm is 750 but it will smoothly rise by 125 when the A/C cycles on and then back to 750 as it cycles off.
Idle is never rough though.

locksmack · Postby **locksmack** » Sun Oct 13, 2013 9:29 am

Thanks heaps guys.

I am expecting a call from the sales guy tomorrow, so I will mention to him that I will require a test drive before I accept the car (and make payment) to ensure that the idle is fixed and if not, I will refuse delivery. That should be enough of a threat for him to actually get it rectified.

Regarding the cooling off period - google tells me it is 3 days in Victoria. I signed the contract on Thursday arvo, making today (Sunday) the third day. The dealership isn't open today, so does that mean I can back out (citing cooling off) tomorrow if I am not happy with their response?

Cheers,
Lockie

Kuncha · Postby **Kuncha** » Sun Oct 13, 2013 9:33 am

The cooling off period starts the next business day and does not include Sat or Sun.

It will end close of business on Tuesday.

locksmack · Postby **locksmack** » Sun Oct 13, 2013 9:37 am

Thanks Kuncha, perfect.

speed freak · Postby **speed freak** » Sun Oct 13, 2013 5:30 pm

Definitely suss it out before you purchase and take delivery like the others have said.
Next time you test drive I would drive it with air con on and off and check anything else you can think of.

I have a similar issue with my NB that I purchased from a dealer, when I test drove it we had the air con on not thinking at the time to turn it off and drive with it off also. I didn't notice until I had purchased it and taken delivery that with air con off it does this weird thing when slowing down in gear with no throttle when the revs drop to 1500 rpm it jerks back and fourth and is really rough. Still to this day I have no idea what it is no one seems to be able to solve the issue.

Good luck with it hopefully they fix it for you otherwise Id keep looking.

locksmack · Postby **locksmack** » Sun Oct 13, 2013 6:18 pm

Thanks mate.

I'll definitely be sure to test drive before delivery. Come to think of it, I did turn on the AC right before I noticed the idle as the windows began fogging up. I'm really kicking myself that I didn't investigate further, I guess I was too busy checking out the other aspects of the car. What seemed like such a small detail at the time is now playing on my mind. I guess thats what spending tens of thousands of dollars will do to you.

The previous owner was a member of an mx5 car club (sales guy told me and a sticker on the window). A long shot, but I wonder if by chance anyone here knows of this car? Rego is ZZO511 and it is a Red PRHT 2008 model. It was traded-in in or near Epping (North of Melbourne).

Either way, as suggested I always have the cooling-off way out.

JayMo · Postby **JayMo** » Wed Oct 16, 2013 9:14 pm

Mine does this every time the battery gets disconnected, goes on for about 1000km... I am interested in the why myself... always run 98 in it...

regards

John

PAU61L · Postby **PAU61L** » Wed Oct 16, 2013 10:59 pm

As JayMo said, mine also runs rough for a while after battery disconnect, reconnect or a flat battery, ask the dealer about the battery cond and whether the battery has been disconnected or jump started,
Paul

JBT · Postby **JBT** » Thu Oct 17, 2013 5:59 am

I've disconnected my battery twice over the years but did not experience rough idle after reconnection.

93_Clubman · Postby **93_Clubman** » Thu Oct 17, 2013 10:46 am

JayMo wrote:Mine does this every time the battery gets disconnected, goes on for about 1000km... I am interested in the why myself...

Don't know if this specifically applies to the NC ECU, but when this happens on some other ECUs it's because the ECU is relearning.

JayMo · Postby **JayMo** » Fri Oct 18, 2013 9:00 pm

93_Clubman wrote:
JayMo wrote:Mine does this every time the battery gets disconnected, goes on for about 1000km... I am interested in the why myself...

Don't know if this specifically applies to the NC ECU, but when this happens on some other ECUs it's because the ECU is relearning.

Yeah got that it is relearning... moreso don't understand why it is off by that far that it hunts so much...