Rev hang on cold starts

[tricker_luke]

Mine still does it, just after starting up if I put the clutch in the revs hang, but it does drop if the throttle is blipped.
I just think it is more noticeable with a loud exhaust!

 

[tricker_luke]

And the starter motor screech is fixed with some grease on the moving part, just take it off and grease it up

 

[c4irney]

Yeah mine has an exhaust so the whole street hears it in the morning. I've been fixing/building engines for years, built my dc2 turbo aswell so have a good understanding of how it all works and i reckon it can only be the IACV either sticking or the ecu keeping it open too long. Might try the IACV off the wife's ep3 and see if it changes, if not, it must be the ecu. I'll report back once I've tried swapping them. Anyone running KPRO have the same problem?

 

[wj51fut]

And the starter motor screech is fixed with some grease on the moving part, just take it off and grease it up

I've had the whole thing apart before and after 3/4 weeks it starts again. Any good tips on how to do this properly?!

 

[TheH]

I dont think the ecu would be the problem,mine does the same even when i run the mugen N1 or the Oem ecu with either Oem manifold or the DC sports,i think on k20a.org there is a Diy on how to clean the IACV i think he uses a compressor to blast air inside and allow the spindle thingy to spin alot faster than it usually would to free it up.i have to get around to do this myself

 

[anton1234]

I've had the whole thing apart before and after 3/4 weeks it starts again. Any good tips on how to do this properly?!

The starter motor issues IMO is down to the CCA of the battery,as we all know the size of the battery is rather small for the size of the car and if the battery isn't up to its best and now that the weather is starting to get colder the CCA can drop by a significant amount

This can cause the starter motor to not retract quick enough from the ring Gear on the flywheel hence the noise

From my own personal experience mine would always do it in warm or cold weather from start up until I replaced the battery to one with a higher CCA, if the car is not used for a few weeks I will leave it on a trickle charger to keep battery at its best and for the past year I haven't had the noise once and I've never added any grease

Id imagine a bit of grease would help a bit to lubricate but I think it's just covering up the underlying battery issues, I'm not saying my way of thinking is 100% correct but from my own experience this is what I have found, hope this helps

Anton

 

[c4irney]

^^ I agree

Mine only seems to do it if I haven't driven the car a reasonable distance the day before. My commute to work is about half a mile so doesn't really get a charge. If I go a drive for a drive the night before it doesn't do it. Going to replace my battery soon, goes flat really easy after a short while with the stereo on

 

[beppe786]

It's annoying I know but they all do it. It's like the starter motor screech. They all do it eventually.

i took my starter off and sent it away for testing all it needed was grease it and its fine no noise..

 

[c4irney]

Right guys I've finally found what is causing this problem!! There is a thermostatic valve, one end goes to the airbox and the other end goes to the inlet manifold. There is little chambers on the inlet manifold that run to each injector. From a cold start the valve is open allowing unmetered air through the inlet manifold to the injector port to help the fuel atomise better and help speed up warmup. However, this acts like a vacuum leak causing a higher idle and more annoyingly causes the revs to shoot up when you dip the clutch. This valve is called an 'idle air assist valve' and can be deleted/bypassed without any bad effects, the car will just take slightly longer to warm up. I pulled off the 2 hoses and plugged them with bolts just to test and hey presto!! Ep3's also have this valve however I've had 3 ep3's and it's never been a problem.

I actually found this out by mistake, I had the induction kit off my dc5 and started the engine. I noticed a strong vacuum from one of the hoses and when covered the idle settled down so done some research and came across this.




And here's a pic of my ghetto bypass just to see if it fixed the problem. Now I know it has I'm going to tidy it up a bit




You can thank me later

 

[coyote_dc5]

Tegiwa do a delete kit for 20 quid I believe if you have a spare 20 note lying around

Sent from my Z10 using Tapatalk 2

 

[scottj15]

Interesting. I posted about this recently yet mine seems to have started sitting rather high when its warmed up too. Not as high as when its cold but still quite noticeable. Think I'll have a look at this at the weekend and make sure all the hoses are secured tight. Nice one.

 

[integraleo]

Before last couple posts I was going to say it's definitely not the idle control valve as I bought a new one from honda at a cost of 250 quid!! And mine still does it. I have k100 too and with k100 or kpro the benefit of these being the standard honda cold start options still used even after mapping.

 

[c4irney]

The idle air assist valve (IAAV) should close after warmup, if your idle is staying high when warm it's either the IACV or the IAAV. You can quickly test the IAAV, when the engine is warm remove the hose from the airbox that comes from the valve and cover it with your hand, your idle should stay the same. If it drops then the valve is stuck open

 

[RNP]

Had to revive this old thread because my car's RPM was stuck just under 2000rpm on a cold start and didn't drop. It usually decreases incrementally with increasing engine temp, but this time it just hung. Thought it could be a IACV issue but it was interesting to learn about the IAAV and I'll check it out tomorrow. Can the IAAV be cleaned like the IACV? and does anyone know the part number for the IAAV? Thanks.

 

[Johngreen537]

Give it a vtec blast blastfor 20 mins. That sorts it 99% of the time

Sent from my LG-H850 using Tapatalk

 

[RNP]

vtec for 20 mins? Woah...I'm pretty sure the cops would be on me before I solve that problem. haha. Probably looking for a more full proof solution because I'm sure it would pop back again.

 

[tricker_luke]

I forgot about this post. I just cable tied the pipe to block it for now and the surge has now gone. There is minimal higher idle when cold, but I don't sit around waiting for it to warm up anyway so it makes no difference.

What it has improved though is when cold, the car doesn't want to keep driving as quick with the higher idle and when depressing the clutch the revs stay low rather than shooting up!

I'll give it a couple more days before a permanent fix.

 

[RNP]

what would be the permanent fix? i actually got the IACV and TB cleaned (installed the ktuned TPS v2 while i was at it) and so far so good! I heard it's not really posible to clean the IAAV.

 

[tricker_luke]

Permanent as in a blanking cap haha rather than cable ties.

Update, the car must have been slightly warm because it does still idle higher when cold but it stops that surge and hang of revs when the clutch is dipped.

 

[MissMyDC2]

I found that my iaav was broken and had been for an age so I removed it and put in a K-tuned blank. It was useless and leaked like a sieve. I tried ptfe on the main thread and it leaked out the sensor grommet. We I had the engine rebuilt I fitted a second hand iaav and now works prefect. Yes it does idle high when cold but doesn't hunt anymore.

K-tuned one was a waste of money.