FN2 running issues

[crazzzydave]

Hi all. For the last year or so, I've had this continuing running issue with my FN2. So far, dealerships answers have been " no fault apparent" or "they all run like that" and finally "it's a characteristic of the FN2's". It didnt do it when I first bought it, it just gradually appeared and now is at it's worst. Has been doing it from I'd say around 48 thousand miles onwards. Engine management light has not been on, and apparently the car shows no problems when on the diagnostics. The car is a 2008 and has done 57 thousand miles. She is always serviced and has FHSH. So here's the problems...

Problem 1 Driving whilst engine still cold.

When driving her from first start up, she is really difficult to drive. If using light throttle, the car just Kangaroos and is bloody annoying to drive. Just no smoothness at all. trying to keep to 20mph and 30mph limits is nigh on impossible to do as you would in any other car, it just kangaroos like it's on drugs! So you end up using more throttle (although this highlights problem number 2 more!) and end up over the speed limit. Not good!

Problem 2 Driving when engine cold/up to temp.

This second issue is also very annoying! Even when warmed up, this issue is there, although most noticeable when the engine is cold. Again under gentle throttle the car is sometimes quite jerky, and have noticed that there is a very noticeable "flat spot" if you are trying to accelerate from just under 2000rpm. There is a what I can only describe as a "pause" when you pres the throttle and when the power does come through it is slightly jerky, as in not smooth? It's almost like the engine bogs down for a second (you can hear it in the engine note) then decides to go? Hard to describe it. This happens in any gear, and mostly at lower speeds, but have also noticed it when at around 60-70mph if you accelerate it kinda pauses/engine bogs down before it goes.

The only mod engine wise is the HKS RSX kit, but it was doing it before fitting that anyways. Everything else engine/exhaust wise is standard FN2 stuff.
Would really like to get this sorted as it's impossible to drive the car smoothly. I'm thinking both issues are both probably caused by the same fault. Just don't know what that fault is. I've been around a lot of the forums and get various answers but nothing solid. Don't want to waste loads of money replacing parts that don't need replacing if I don't have to. Anyone here kn ow what the issue is most likely to be?

 

[Loxy]

HKS RSK does cause a flatspot for some people under 2k.

It does sound like what you are doing both when then car is cold and warm is effectively labouring the engine. Say if you wanted to going 20 mph when cold, I'm guessing you will be in 4th gear which means the revs are too low. If you use 3rd gear instead you won't get the issue as your engine speed will be higher for the same road speed. You need to modify your driving style. It is a highly strung NA engine that revs to 8,200 rpm and they don't like being under heavy load at low revs, particularly when cold.

It it a characteristic of the car, but you just can't drive them around on tickover when they are cold and they don't like accelerating from under 2k when warm, and the HKS (for some people) doesn't help with that.

It could be a throttle pedal fault, but to be honest from what you've said, it really does sound normal.

 

[crazzzydave]

Thanks Loxy. I doubt its my driving style though as the cold engine problem is there at low speeds even if i'm in 2nd gear at 20mph, it's really bad. If I tired 4th gear at 20mph The thing would almost deffo be impossible to drive, would either try to stall or just kangaroo to a stop. I know these things love to rev, been driving Hondas for over ten years now and this is the only one that's had any issues with flat spots/erratic driving when cold. I cant believe Honda would create a car with a "characteristic" that makes the car feel like somethings wrong with it? I've heard such varying stuff in the past it's hard to know what is right, some say theirs does it, other say theirs drives fine whether cold or warm. It deffo shouldn't bog down like this though, so thinking there has to be a fault with maybe the o2 sensor, egr valve or poss throttle position sensor. So may possibles! lol Thought about the fuel filter too, thinking maybe not enough fuel getting through for that split second?

One thing I have noticed. If I'm doing say 20mph in 2nd and the road is really bumpy, the problem of kangarooing s really exagerated even more. Which makes me think that it could well be the TPS, maybe if your foot bounces ever so slightly on the pedal due to bumps it could be enough to cause it if the TPS is faulty?

 

[Shoonk]

You could try cleaning out the throttle body first with some carb cleaner, that will be your cheapest option but I had something similar with my EP3 but not as bad as yours by the sound of it.

It would kangaroo when cold but wasn't too bad when warmed up for me. I got it checked out there was no EML on or anything but it turned out the O2 sensor was on it's way out, (mechanic said on the diagnostics it was showing wrong readings) so got that changed and all is fine. I'm sure it was the pre cat sensor that was my issue. But as you've mentioned it could be the TPS also.

It's difficult to pin point exactly as it could be a few things but, as you said, you don't want to spend loads of money on the issue. I would try cleaning the TB first as you can do this yourself, if it helps you can concentrate on that area otherwise you may want to explore the other options.

 

[crazzzydave]

Hmm, o2 sensor sounds probable mate. Is there any how to's for cleaning out the TB? Might be worth doing that too just to see if it makes a difference to it. Will price up an o2 sensor from Honda (and get ready to be shocked!). I take it there's just the one o2 sensor on these?

 

[crazzzydave]

Thinking about taking the HKS RSX back off her as it does seem to highlight the issues even more. Thing is, love the noise she makes with it!!! lol

 

[Loxy]

There are two O2 sensors, one pre and one post cat. It's a good shout to be honest. They are about £130 each IIRC, but Tegiwa, Hendy and Cox in the traders section sell them at probably cheaper than list price.

Carb cleaner into the inlet for the TB. It is an electric TB, so there isn't a lot to get stuck really as the motor for it is the black thing on the back of it.

 

[crazzzydave]

£130 each? Thats not too bad then! Think I'll give the above traders a call then mate and start with replacing those. I'm sure I head that about those bloody sensors before, in that they can be fecked but show nothing on the diagnostics. Just be nice to get rid of this problem. What do you reckon about going back to OEM filter? Good idea?

 

[Shoonk]

I think the throttle bodies are different on the fn2's with the ep3 I just took the hose off of the throttle body and sprayed carb cleaner on the butterfly valve just to clean possibly free it up. On the ep3 you can open the valve manually not sure if you can do this on the fn2 if it's electric but may help a bit.

IIRC the O2 sensors for the ep3 were closer to £200 each you can get cheaper aftermarket one's but they wouldn't last on the ep3 for some reason so I would advise to get genuine OEM one's.

 

[crazzzydave]

Yeah, would be going to Honda for them mate. A lot dearer but at least they won't fail! Had problems with the ignitor in the dizzy of my old mb6, and the parts guy at Honda got me a pattern part (to save money) Pattern part was £90, Honda part was £250. So, 4 weeks later, and 3 pattern parts later, got the proper one! All pattern ones lasted just over a week max!

 

[Jo5h]

Although mine is an EP3 it has done exactly what your problem #1 is describing, had to just put up with the jumping until a bit warmer. Did seem worse on colder mornings though, it was in May mind so not like this time of year!

That was both/one of the O2 sensors, the EML came on not to long after it started which pointed them out as a problem.

 

[crazzzydave]

Thanks mate. Yes, it's deff sounding like those are the culprate now. Will need to wait till next month to get them as a few big bills have landed with a thump on my floor! But will be good to get these changed and see if it cures it!