Hesitation/flat spot problem with Honda Accord

Howard

Howard

Howard

Soldato
Joined
12 Jul 2007
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South East
Hi folks,

Thought I'd make a thread here in case someone may be able to shed some light!

My old 2000 Honda Accord 2.0 (my Dad has it now) has, since I've had it (and has done for years) a slight 'flat spot' at exactly 2,500RPM when under load, noticeable in lower gears, but mostly in 2nd and 3rd. The symptoms are if you're accelerating hard, i.e. WOT from low RPM through the revs, you'll feel a slight jolt as it passes 2,500RPM.

It didn't bother me as it's not THAT bad but my dad is very curious.

We've tried everything we can think of, including:

New plugs
New leads
New fuel filter
My dad took it to Honda who spent 4 hours looking at it (but don't worry, they didn't even charge him an hour's labour) and said that the distributor cap/rotor are fine, all the sensors are fine, all vacuum pipes are fine, nothing appeared on any diagnostic equipment. They don't know what to suggest without spending god knows how many more hours investigating.

It's had pretty much every other consumable part I can think of! Even a new clutch, although I'm sure that's not relevant ;)

We're out of ideas! My only remaining theory is that it's something to do with the engine management and some sort of mapping discrepancy, but I'm not sure what can be done about that.

Anyone?!

Thanks!


Edit: FYI, it's a 2L SOHC 16V VTEC engine.
 
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hmm might be something like a variable intake switch-over, but im not particularly familiar with the engine so couldnt give more than a guess :(
 
It doesn't have anything fancy like that. Only other thing that springs to mind is something to do with the VTEC actuation but 2,500RPM seems a bit low
 
My mondeo has an issue very similar to this at very similar RPM. I just ignore it because I don't want to spend any money trying to fix it but I'd be interested to see if you solve it.
 
When does the V-TEC kick in, in this engine?

The reason I say this, you can get hesitation when entering V-TEC when the timing tensioner is wearing out, or when your oil levels are low. But obviously if you're not entering V-TEC then it won't be this!
 
I did wonder if it had something to do with VTEC but 2.5k seems a bit low, even for the 'economy VTEC' engines?
 
Howard said:
I did wonder if it had something to do with VTEC but 2.5k seems a bit low, even for the 'economy VTEC' engines?
Click to expand...

It's massively low, but I don't pretend to know everything about engines and different variations of them! :) V-TEC usually kicks in around 6000 rpm mark, but I have no knowledge of this engine so can't comment!

V-TEC does have a built in fail safe when low on oil, it will just not let you engage V-TEC or hesitate until it feels fine.

Have you checked your oil?
Do you get any rattles? A rattle at idle or just above idle (1500 rpm) plus hesitation would be a decent shout for the timing tensioner.
 
It's had plenty of oil changes since I got the car in 2007 and is checked regularly :p No rattles, the engine runs absolutely perfectly otherwise
 
It's a good one then Howard!!

I'm just pulling on my s2000 experiences and reading the forum, so it might not entirely be accurate for your old mans Accord.

Low down hesitation on the s2000 could be coupled with 'kangarooing' does your old man get this?
Have you driven the car since? Are you sure he's driving it correctly? All V-TECs as I'm sure you are aware need to have the nuts revved off them and can feel very lame at lower speeds.
Is he flooring it from a higher gear, rather than dropping a cog or two and going from there? If so, drop the cogs down!
S2000's do have a bit of a characteristic of taking a fraction of a second (which can feel like a flat spot) when flooring it at lower speeds / RPM. It's a bit of a characteristic of the engine in all truth. When you owned the car did you notice it at all? Has it definately not always been there and you've never noticed it due to a different driving style?
 
Are there any oil leaks around the head area?

My mate had a similar problem on his ATR and Skywalker seemed to think it was due to leaking camshaft end seal(?) or possibly the VTEC solenoid or something.

Terminology is probably out - I was only half listening to their conversation at the time (someone has to do the hard work)
 
hilly said:
It's a good one then Howard!!

I'm just pulling on my s2000 experiences and reading the forum, so it might not entirely be accurate for your old mans Accord.

Low down hesitation on the s2000 could be coupled with 'kangarooing' does your old man get this?
Have you driven the car since? Are you sure he's driving it correctly? All V-TECs as I'm sure you are aware need to have the nuts revved off them and can feel very lame at lower speeds.
Is he flooring it from a higher gear, rather than dropping a cog or two and going from there? If so, drop the cogs down!
S2000's do have a bit of a characteristic of taking a fraction of a second (which can feel like a flat spot) when flooring it at lower speeds / RPM. It's a bit of a characteristic of the engine in all truth. When you owned the car did you notice it at all? Has it definately not always been there and you've never noticed it due to a different driving style?
Click to expand...

It's been there since I've had it, as I mentioned in the opening post ;) It's nothing to do with driving style, it occurs as the revs hit 2,500RPM and is noticeable in lower gears. It may be a VTEC engine but tbh it feels like any other 2.0. It's not a performance twin cam VTEC sadly :( Lol

I don't think there's any oil leaks, no!
 
hilly said:
It's massively low, but I don't pretend to know everything about engines and different variations of them! :) V-TEC usually kicks in around 6000 rpm mark, but I have no knowledge of this engine so can't comment!

V-TEC does have a built in fail safe when low on oil, it will just not let you engage V-TEC or hesitate until it feels fine.

Have you checked your oil?
Do you get any rattles? A rattle at idle or just above idle (1500 rpm) plus hesitation would be a decent shout for the timing tensioner.
Click to expand...

Isn't that due to cam switching? Eco vtec is very different and kicks in at nothing like 6k afaik.
 
loltim said:
Isn't that due to cam switching? Eco vtec is very different and kicks in at nothing like 6k afaik.
Click to expand...

Like I said, I have no knowledge of this engine mate! It could well be, I honestly don't know when it kicks in. But just speaking out of experience after owning an s2000 for 16 months.
 
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