Hanging revs between shifts
 

Hi guys and gals! A couple of weeks ago I was in a front end collision which has put my Tib in the ICU but in the meantime I went ahead and picked up an 03 XD Elantra. Everything is fine and dandy about this car but I noticed that the revs are weird in between shifts. For example, say I'm accelerating and go to shift from 1st to 2nd, the revs will jump up about 300RPM and hang for about a second and then drop down. Now this doesn't sound terrible but it makes it a pain when trying to shift normally.



At first I thought maybe my foot was hitting the gas but it clearly isn't. I can somewhat get around the problem by taking my foot off the gas pedal for about a second before shifting but that's not feasible all the time. The issue doesn't seem to be apparent when the car is cold either. Also, if I'm just coasting in gear and push the clutch in, the RPMs drop immediately. I also will note that it doesn't seem to happen as much when I really romp on it and shifting around 5-6K. I've been doing research (outside of HA) in regards to this and have come across articles saying it might be a feature imposed by Hyundai to help inexperienced manual drivers. Does anyone know if there is a way around this?



Possible gummed up IAC? Need to slacken the throttle cable? Reset ECU?



Thanks for any insight!

Slave cylinder mod. Search a diy here on HA there is a restrictor in the slave cylinder that will slip the clutch a little for smoother shifting for the inexperienced. Doing this diy makes a real difference try it out.



Edit-here you go DIY

Sounds like a sticking IAC to me.

I don't think the slave cylinder mod would be the fix here but it's something I can look into. My thinking is if the throttle cable was too tight, the car would always idle high but that isn't the case. I'm going to try to clean out the IAC this weekend. Any other ideas?

From what I have seen from other experience and my own that doing the mod has stop the rpm jump. The usual jump was about 300 rpm before the mod. If you feel like its something a little more dramatic then it might be something else.

I guess I just don't see the correlation between the slave cylinder and the jumping/hanging revs. I'll keep poking around though.

vacuum leak possibly? does it ever stumble at idle, or just run rough?

Nope. Car runs flawlessly minus the rev hang.

Spoolinshark, it's a tactic to reduce emissions. The ECU can more accurately meter fuel when the revs don't drop so fast, so even though it might not be in closed loop, it's better than dumping TPS enrichment down the exhaust. I digress.



All you need to do is get some sheet aluminium and make up a restrictor plate for the ISC. It's pretty simple, I just took the ISC off, traced around it onto some aluminium, cut it out with tinsnips, and used a holepunch to get the holes right. Start small and step up the hole size until it's juuust big enough to prevent the car from stalling on a cold start.



I have done this on three X3s and by beta II swapped LC. It's a ridiculous improvement for bugger all time/effort/money.

I forgot to mention that the car is throwing a P0133 code, slow response from O2 sensor bank 1, but don't think it would have that effect. But it could.. Also, what is the ISC? That acronym isn't ringing a bell at the moment.



Edit: ISC is Idle speed control correct? Same thing as the IAC?