Engine rev's increase when changing gears =\ - Honda Prelude Forum

Mattimus · 03-02-2010, 12:27 AM

Hi guys, I've searched the forums but haven't come across any mention of the problem I have with my 92 Prelude Si. Every time I change gears (just driving normally), when I push the clutch in, the engine rpm increases about 100-200 rpm. Its not a serious problem but its a little annoying and I was wondering if anybody else has had this happen and if so, why does it do it? I can't think of any reason other than maybe extra air? It's like I take my foot off the throttle but there's a tiny delay (throttle response?) before the fuel cuts back and the rev's drop back down as they are supposed to...

If anybody has any idea's or personal experience please feel free because I'm puzzled lol...

Cheers.

Machine Head · 03-02-2010, 11:56 AM

I recall having this issue after swapping in my engine. it turned out it was a vaccum leak and a minor timing adjustment

Mattimus · 03-03-2010, 04:39 PM

Thanks for the fast reply. Ah ok. Well my mechanic checked my car for vacuum leaks a few months ago and he didn't find any :S When you say 'minor timing adjustment' do you mean just rotating the distributor cap slightly? I'm not sure how that would make the difference though....

Another thing I've just realised when I was looking closely at my engine is that on the top of my intake manifold, just next to the idle adjustment screw, it has P13. I read somewhere that the H23's use P14 ecu's and the H22's use P13 ecu's.... Could I be using an H22 ecu?! My H23 performs really well on the road so I would assume I'm running the right ecu?

red92si · 03-08-2010, 10:27 AM

No. The top part of the intake manifold was shared between H23 and H22 engines. That is why it is marked P13.

Da_lude · 03-08-2010, 01:27 PM

My lude does it too and so does my brothers 09 Civic Si, I know they are drive by, but the only reason i can think of any car doing it is to maybe to help for a smoother shift?

Im just throwin out a possible idea, I have no clue. I do know that when I use to run my a4 on a p28 it didnt do it, but when I put the stock one back in it did do it..

mEtaka · 03-10-2010, 06:32 AM

Hey boys, I have the same problem. Have anyone of you check the Throttle body for dirt?
P.S. Sorry for my english

theschwag420 · 03-10-2010, 08:56 PM

hey guys i used tohave the same problem in my car amd it was the throttle cable sticking

Mattimus · 03-10-2010, 11:20 PM

Red92Si: Ahh ok thanks for clearing that up.

Da_lude: You may be right in that the ecu is programmed to do it (perhaps like you say, for smoother shifting) but I wish I could stop it, because it does start to annoy...

mEtaka: Yeah mate I took my throttle body off a little while ago and hit it with the carby cleaner. DAM was there a lot of dirt and carbon built up. Looked so nice once it was clean. I didn't notice any obvious changes though.

theschwag420: Ah ok. How did you fix the sticky cable? Just some WD40? I wonder if mine is sticking, in my opinion it doesn't really FEEL like its the throttle cable sticking but then again...

To me it feels like the engine is somehow sucking in more air (like a vacuum leak or something - even though my mechanic checked mine for any leaks) as my car is always feeling like it wants to rev alot. (It's also a victim of the high idle problems/surging.)

[The only solution to the surging I could find was blocking off the FITV - which kind of fixed it, it stopped the constant surging, but when I pushed down on the clutch, the rpm's only drop back to around 1300rpm-ish, then after a few moments, the idle will lower back to 900-1000 (which I know is still high but it seems to be as low as it will go) =\ However, the engine still surges a bit every so often. Again, feels a bit like there's extra air getting in there somewhere, I dunno

...... ]

Sorry to get off topic there but it just feels like they might be connected somehow...

Matta1 · 03-11-2010, 06:40 AM

It really sound like the throttle isn't released 100%. It could be both a sticky throttle cable or carbon buildup in the throttle body. Same happened to me. Since you have a high rpm when it's in free, it could indicate that the throttle is still a little pushed in. Try taking your foot under the gas pedal and pull it a bit up, or go under the hood and push the throttle back to normal position (won't move much, but should do the trick). If your rpm drops to 500-750, you atleast know what's causing it.

(When I did this, my rpm went from 800 up to 2000 and down again. That's how I diagnosed my IAC valve as well

Mine was always idle at around 1500 rpm)

Hope this helps

BTW, I hope that the FITV block is just a temporary fix. You should look around on the forum on how to fix it more permanently.
I.e: HELP!!!! idle prob *vid*
Just a thought

Mattimus · 03-12-2010, 04:07 AM

Hmm well I have played with the throttle a bit (tried pulling the pedal outward and pressed on the throttle under the hood) but didn't notice any change but I'll try again.
I've already replaced the IACV ($330 - thankyou Honda >_>) but it didn't change anything...

Yeah I'll have to reconnect the FITV sometime, it's just the thought of having the rev's surging again makes me cringe at the idea. I did screw the FITV plastic screw thing back in and reattach it but it didn't stop the surging - which was when I decided to just block it off completely. I will try bleeding the coolant some more and see if that helps - I'm just skeptical that some air bubbles in the coolant could cause the idle to fluctuate so consistently?? I mean, wouldn't the surging be more random? Or would the air bubbles get stuck inside the IACV itself thus... ? I dunno... lol anyhoo...