very fast idle surge

[maxpower98]

ok i have had my j35a4 in my ek for about a month now and have been driving around and sorting out the small things. one thing i have not been able to fix is sometimes randomly the car will start to idle surge very fast. the rpms dont raise very high, just a few hundred rpm. the way it acts i dont think its the iac valve. i say this because it effects the way the car acts while driving. while starting off the car will buck and jerk with the surges. any suggestions would be great.

[wolydotmatrix]

Most idle surges are from some form of vaccum leak or unmetered air. This means any place behind the throttle plate. For example T-body gasket, Iacv, idle screw, IM gasket, plenum gasket, vaccum line. The map sensor and the MAF or some cars measure the volume of air passing the throttle plate-> ECM/PCM adjusts fuel for that amount of air. So if there is air coming in from another source the idle will surge.

Surge will be amplified at lower engine speeds (surge/Buck) like when rolling out slowly from a light. Just my0.02

[StolenLegacy]

Ive been dealing with this for the past few months with my stock eg si.. When u first run it and its cold the idle surges and it bucks but when it gets up to temp it "pops" and it acts like nothing happened to begin with lol. Ive changed my iacv,IM gasket, and am currently looking at my vac lines. Does yours do it ALL the time? Or does it just stop suddenly after it warms up?

[maxpower98]

woly- at first i thought it was a vacuum leak. i checked and rechecked everything. the weird thing is that the last time it acted up i hooked up our hds at work and scanned for codes. the normal auto trans codes and secondary o2 code but nothing else. so i cleared all the code and restarted the car. it has ran fine for 3 days. so i feel its hard to be a vacuum leak when it doesnt happen all the time.

[wolydotmatrix]

Three days with no issues may not be vaccum related. Double check you STFT and see how checks out on the datalist. Should float above and below Zero. Leak would come out +1 and stay above zero as the ECM is trying to add fuel for lean condition. Wait until it messes up then look at you data list.
ECT will cause issues as well. reading cold when hot or vice versa.

Still think it could be leak some where. I fixed mine with a new TB gasket,hairline crack from when I swap TB's and the gasket stayed on the plenum or so I thought. Are you using some type of solvent(carb cleaner/tbody cleaner to find leaks?

[maxpower98]

ok ill have to look when it acts up again. and i checked for leaks a few ways, one with carb cleaner all over the vacuum ports and throttle body areas and i also filled the intake and crankcase with smoke from our smoke machine to see if there were any leaks from the lower intake or intake spacer. neither showing anything. all the top end gaskets are new from the valvecovers up. a vacuum leak still doesnt explain why when i cleared the codes and restarted it i havent had a problem since.

[3.2em1]

hey i might be bring up swap up to toledo tomorrow night for something to do not sure if you go out and hangout with everyone at night but if you do bring it out maybe we can figure out what it is.

[wolydotmatrix]

ok ill have to look when it acts up again. and i checked for leaks a few ways, one with carb cleaner all over the vacuum ports and throttle body areas and i also filled the intake and crankcase with smoke from our smoke machine to see if there were any leaks from the lower intake or intake spacer. neither showing anything. all the top end gaskets are new from the valvecovers up. a vacuum leak still doesnt explain why when i cleared the codes and restarted it i havent had a problem since.

Ah the smoke machine, I miss working at the dealership (sometimes). Good idea though. Mine didn't show up either with carb cleaner. I used a new J30 gasket from an EGR kit and it was close but did not seal the ports on the T-body correctly. New J32 gasket solved my idle issue.

What rpm is the surge? Worse cold or hot?

[maxpower98]

Ah the smoke machine, I miss working at the dealership (sometimes). Good idea though. Mine didn't show up either with carb cleaner. I used a new J30 gasket from an EGR kit and it was close but did not seal the ports on the T-body correctly. New J32 gasket solved my idle issue.

What rpm is the surge? Worse cold or hot?

the surge is only at idle or right off idle. and it is only like a hundred or two rpm. i have a s2000 cluster and it barely reads on that but with a multimeter you can see it. it doesnt matter it has happened after driving a bit and also right when i start it up. if i turn the car off for a minute or two and then restart it will still do the same thing. i clear the set codes and restart. perfect. i like the dealership... warranty is fun to get some needed stuff for the car. lol

[wolydotmatrix]

Have you tried adjusting your Racv?
Remove these two screws (tamper proof like on the TPS)and the valve will rotate rt and left. One way idle up, one way idle down. Have had to do this before on other j-swaps when nothing else worked.
http://i350.photobucket.com/albums/q413/wolydotmatrix/T-body-1.gif

Air trapped at the RACV can cause an idle surge as well. Is your radiator lower than your outlet on the cross-over?