DuecedSol

The problem at hand:

Ok need some help, I just installed a TSX throttle body using a Z3 paper gasket, P2R spacer and then thermal gasket. But of course I've got a problem. I have a idle surge. It occurs under two different circumstances. First with the car not moving, giving it gas off idle it will rev up fine fall to about 1k then back up to 2k then slowly back down to idle. 2nd, while cruising when clutch is depressed and no throttle the rpms drop to about 1k then back to 2500k and repeats that till the car stops them it will slowly makes way back to idle. The car idles steady at 850 with no accessories on. Climbs through the rpms fine all the way to redline. Another issue I've noticed is the rev hang is worse than it used to be. It almost revs up between gear changes. And while cruising if I let off the gas while still in gear it takes a full second before throttle is pulled and the car starts decelerating.

What I've done to try and fix:

I've followed the first post of this thread DIY: Throttle Body Calibration Procedure step by step( other than using flash pro as I currently do not have it, only engine mods I have are the throttle body and spacer). I did the idle relearn(vit vipers process),pulled the dbw plug, adjusted the set screw till it idled at 1K, turn the car off, plugged in dbw, then key back to run position, tested voltage and adjusted the set screw accordingly, both are within spec(note i used the battery ground instead of SG if that makes a difference), turned key off and waited, started car and let idle for maybe 10mins or more, took it for a 10min drive, let it cool down then drive it again for maybe 30-40mins, let it cool again, then another 30-40min drive...still have same symptoms with no improvement.

My next step as of now:

I'm going to drive it all week and see if it improves, if not then my only theory is a small vacuum leak somewhere. I have a HPS intake tube on the way so next weekend when I put that in I may pull the TB and reinstall to make sure everything is sealed well. I've ready through countless threads on this and similar issues with no real answer, Any help or thoughts would be great!

Update:

Got about an 8 min drive to work this morning, still had the same symptoms except I noticed when I parked it was idling at 750 so maybe that was a sign of things fixing themselves. So on my first break today I went out and started it and let it run for 20mins. Rad fan kicks on 3 times during the 20mins, but idled at 850 the whole time. Did a few throttle blips and it would rev up fine then drop to about 1k and back to 1500 then slowly back to the 850 idle...Everytime.

Update:

So I decided to try the relearn again, this time I disconnect both battery cables and left them touching each other for a little over an hour. Then started the car and let it run for 30 mins. At this point it was idling at 850, so I turned the car off and restarted it quickly and rpms jumped to 2k and slowly came back down to 850 again. Still does the idle jump when I blip the throttle, revs up fine falls to about 1100 then up to 1400 then slowly back to 850. I'm stumped, oy thing I can think of is a very small vacuum leak. Note it still rpm jumps by maybe 500 between shifts, not to be confused with idle surge, along with a slow idle surge when coasting in neutral...i also restarted the car a few times (fully wamed up) and evertime upon startup the rpms jump to 2k then slowly come down to the idle of 850.

Note no CEL at any point during this whole thing.

DaveSi677

That sounds like the IACV intake air control valve. Did you clean the IACV? It could possibly be stuck so that is why the RPM are jumping up and down. The IACV just needs to be cleaned out this is a normal/common thing. Under the throttle body there are two 5point star screws. You can notch them with a dremel to get them off. Your IACV will come out, clean it with some carb cleaner and make sure it spins freely, then re-install it. Turn on your car and start her up.

Try it and keep us posted!

DuecedSol

Thanks for the reply! I will try that tonight!

DaveSi677

Keep us posted!

There are also some videos on how to do it if you aren't too sure!

DuecedSol

Well I couldn't find any videos Z3 specific but I'm sure it's pretty straight forward. The IACV has security torx bits holding it in correct?

Picking up a new paper gasket today as well.

DaveSi677

This should help a little:

DuecedSol

FIXED!!!!
Any one of these things could have been the answer or a combination of things but I'm leaning towards a small vacuum leak somewhere in all the mating surfaces.

Ok here it goes:

-First thing I did after removing the TSX TB, I did the blow test. Basically you hold the inlet of the TB against your face with your mouth on the inside and while gently holding the throttle plate closed from the other side with your finger blow and try to force air past the throttle plate. If it seals properly then the air will force it's way out past your cheeks. Mine sealed properly.

-Next I plugged in the DBW on my stock Si TB and turned the key to the ON II position. I read the voltage across TLH1 and SG along with TLH2 and SG on the DBW plug. The readings I got were .871v for THL1 and 1.694v for THL2. Recorded my results for later.

-I removed the covers from both throttle bodies and adjusted the throttle plate set screw so that the throttle plate closed all the way just shy if sticking. Of course put some thread lock on it. I did notice both covers had the same part number and since I believe they house the TPS and I knew the Si TPS worked properly, I put the Si cover/TPS on the TSX TB. Note this does require a security torx bit.

-Before reassembly I sanded down the mating surfaces of the TB and IM with 320 grit sandpaper then cleaned them with lacquer thinner along with the P2R spacer and thermal gasket. I also used a new Si paper gasket along with a very thin layer of gasket SEALANT on all mating surfaces just to insure a good air tight fit. Less is more in this situation.

-Reinstalled the TB. Now it's time to use my voltage readings I took earlier. Using the set screw on the top of the TB my goal was to try to get the same readings as I did before. After a few try's I got .870v for THL1 and 1.696v for THL2. I was pretty satisfied with that. Thread lock on the set screw.

-I disconnected the battery at this point, both positive and negative and left the cables touching each other while I got everything all button up. 10 mins or so past and I reconnected the battery and did the idle relearn process.

After a quick drive I couldn't be happier with the outcome. The seat of the pants feel tells me low end has improved along with throttle response. The car just feels more alive than it did. I can't say there's a power increase or anything like that but the car definitely drives better. I've got a solid 800rpm standing idle and a solid 1050 rpm cruising idle. No more rev jump or surging. Only thing negative I noticed was a tad more rev hang than with the Si TB but Flashpro will take care of that. Also after a few days of driving I'm sure some aspects may even improve. For me bang for the buck it was worth it, I paid $30 shipped for the TB and $40 Shipped for the spacer and gasket. I only wish the instal went correctly the first time haha

DaveSi677

That is great! Glad to see everything worked out for you in the end.

The TB actually doesn't give you more power per say... although it does give you better throttle response and will help to bring in more air for you Intake to make more power. The spacer will also add 1 or 2 hp at most but still 1 hp is 1 hp no matter what it will help somewhere lol...

Flashpro will cancel out the rev hang... don't be surprised if it takes you a week or 2 to get use too lol! It's night and day difference!

DuecedSol

I agree, the only purpose of adding the TB was to even out the air flow since the outlet is only a 1/2mm bigger than the IM inlet(as I plan on keeping the stock IM). Now it's 64mm-65mm all the way through. It may not add power but will help with future mods. The low end throttle response is well worth it.

Oh I bet! I love the car now, I can only imagine how it will be with Flashpro

DaveSi677

You don't even know... night and day my friend!

tlarimer

iTrader: (3)

I had rev hang bad after installing my TSX TB. Did the recalibration by opening the DBW housing and adjusting the set screw, then did the idle relearn. It solved 95% of the rev hang, it is still slightly noticeable, but been over a year now and I can live with it.

Did notice an increase in driveability, not added power per-say, but it definitely feels stronger through the entire RPM range. Probably my 2 or 3 favorite upgrade I've done.