Rotary_Powerd

When first starting up the engine idles really funny the needle moves up and down alot around 1500 +/- 400. Though a quick small stab to the gas fixes the idle. Once the car is warm idles fine to.

The engine runs really strong. Any ideas of what's up? also when I free rev the engine I noticed that if the revs climb slowly when I use the gas, the rpm's get knocked back down a bit around 1500 rpm.

Bad vacuum line? Bad ground? Other wise like I said she runs great! Thanks for anyones input.

SpeedOfLife

iTrader: (16)

could be a vacuum leak, I kind of doubt it's a bad ground causing THIS issue however you certainly could have bad grounds. could also be your TPS, search for how to adjust it (or there may be a link to a writeup in the FAQ). cruddy idles are a common problem, there should be plenty of information on it. I'm still battling mine, but it got a lot better when I adjusted my TPS back to spec.

Rotary_Powerd

Cool Thanks I'll research the TPS a bit.

Eternal_Gamer

iTrader: (10)

check the tps to see if its in spec. If not that or any vacuum leak, it can be throttle body related such as the thermowax, dashpot, etc. When I had this problem, it was the dashpot, and also the thermowax.

Rotary_Powerd

The funny thing is that it stabilizes with a quick and slight throttle application. Thought the slight RPM fall still happens at 1500 when free revving. I'll take a look at your advice as well.


Darn the FAQs doesn't give specifics on adjusting the TPS. I'll search around a little more, if anyone happens to stumble on anything please let me know, thanks.

SpeedOfLife

iTrader: (16)

Here's a good writeup, make sure you do the LED test because you'll likely get poor results only adjusting it by resistance. I know I did. Also, if you have a turbo model the green plug is to the driver's side between the TMIC and AC compressor and not where it shows in the picture.
http://howto.globalvicinity.com/gv_w...i=58&co=1&vi=1

Hyper4mance2k

iTrader: (40)

99% of bouncy idle problems are a bad AFM... clean it out and make sure it's level and that usually fixes the problem. S4 FC3 and NA3 Miatas are notorious for this same issue.

Rotary_Powerd

Thanks guys it's an S4 N/A. I think it's prob the TPS, but good to know the other options.

AFM = Air Flow Meter?

wthdidusay82

iTrader: (15)

yes afm is airflow meter, my car has the same problem with having bouncy idle but mine is streetported , 5/6 ports all removed, and ported tb. I think mine has to do with my tps setting and possibly the afm but I dont know.

One problem I do have though is I think my brake booster is going, because when at a stop the more pressure I put on the brakes , the idle will drop more and more to the point where the car is barely idling.